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The frequency and incidence of fungi, as well as their interdependence, on rachis and grain of 14 wheat cultivars grown under 19 different agroecological conditions in Serbia, were studied. Out of the 23 identified fungal genera, a significantly higher number of species was isolated and identified from rachides (22) than from kernels of wheat (9). Fusarium and Alternaria species were the most frequent (up to 100 %) species on both, rachides and kernels, but the incidence of these fungi were higher on rachides than on kernels. The most frequent of the 14 Fusarium species were F. graminearum (96.8 % on both, rachides and kernels) and F. poae (93.8 % on rachides and 51.6 % on kernels). The frequency of F. verticillioides was significantly higher on rachides (64.5 %) than on kernels (19.4 %). A positive correlation (r = 0.5356 **) was established between the frequency of F. graminearum on rachides and on kernels. Furthermore, the frequency of Alternaria spp. was also statistically higher on rachides than on kernels, but the correlation was not statistically significant (r = 0.1729). The incidence of F. graminearum was negatively correlated with the incidence of Alternaria species in both, rachides (r = −0.3783 *) and kernels (r = −0.4863 **). These are the first data on the frequency and incidence of fungi on wheat rachides in Serbia, and they support the few data presented in the world literature. Results of this research could be useful for better understanding of pathways in a fungal infection and the improvement of wheat breeding for resistance, as well as, a proper application of fungicides in the wheat head protection.
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Relationships of mycobiota on rachides and kernels of wheat
Jelena Lević&Slavica Stanković&Vesna Krnjaja &
Sonja Tančić&Dragica Ivanović&
Aleksandra Bočarov-Stančić
Accepted: 29 March 2012 /Published online: 14 April 2012
#KNPV 2012
Abstract The frequency and incidence of fungi, as
well as their interdependence, on rachis and grain of
14 wheat cultivars grown under 19 different agroeco-
logical conditions in Serbia, were studied. Out of the
23 identified fungal genera, a significantly higher
number of species was isolated and identified from
rachides (22) than from kernels of wheat (9). Fusa-
rium and Alternaria species were the most frequent
(up to 100 %) species on both, rachides and kernels,
but the incidence of these fungi were higher on rachi-
des than on kernels. The most frequent of the 14
Fusarium species were F. graminearum (96.8 % on
both, rachides and kernels) and F. poae (93.8 % on
rachides and 51.6 % on kernels). The frequency of F.
verticillioides was significantly higher on rachides
(64.5 %) than on kernels (19.4 %). A positive corre-
lation (r00.5356 **) was established between the
frequency of F. graminearum on rachides and on
kernels. Furthermore, the frequency of Alternaria
spp. was also statistically higher on rachides than on
kernels, but the correlation was not statistically signif-
icant (r00.1729). The incidence of F. graminearum
was negatively correlated with the incidence of Alter-
naria species in both, rachides (r00.3783 *) and
kernels (r00.4863 **). These are the first data on
the frequency and incidence of fungi on wheat rachi-
des in Serbia, and they support the few data presented
in the world literature. Results of this research could
be useful for better understanding of pathways in a
fungal infection and the improvement of wheat breed-
ing for resistance, as well as, a proper application of
fungicides in the wheat head protection.
Keywords Wheat .Fungi .Rachides .Kernels .
Frequency .Incidence .Fungal interdependence
Globally, there are more studies and results on myco-
biota of wheat kernels than on rachides. This is not in
accordance with the importance of a rachis pathogen
from the aspect of both resistance of small grains to
Fusarium species (Jansen et al. 2005)andthe
Eur J Plant Pathol (2012) 134:249256
DOI 10.1007/s10658-012-9982-8
J. Lević(*):S. Stanković:D. Ivanović
Maize Research Institute,
Zemun Polje, Slobodana Bajića1,
11185 Belgrade, Republic of Serbia
V. Krnjaja
Institute for Animal Husbandry,
Auto-put 16,
11080 Belgrade, Republic of Serbia
S. Tančić
Institute of Field and Vegetable Crops,
Maksima Gorkog 30,
2100 Novi Sad, Republic of Serbia
A. Bočarov-Stančić
Center for Bio-Ecology,
d.o.o., Petra Drapšina 15,
23000 Zrenjanin, Republic of Serbia
biosynthesis of some fusariotoxins (Voigt et al. 2007).
According to Mesterházy (2002), seven components
(as stated by the author) or types (the term previously
used) of resistance can be identified according to:
pathogen invasion, pathogen distribution, grain infec-
tion, plant tolerance, toxin (deoxynivalenol) accumu-
lation, late infection and death of a spike segment
above the infection point. The component of the first
type of resistance (I) is the infection distribution from
the spikelet into the rachis, while the component of the
second type of resistance (II) is the infection distribu-
tion from the rachis into other spikelets (Bai and
Shaner 1996).
Genera of Fusarium and Alternaria are the dominant
constituents of mycobiota isolated from wheat kernels
worldwide (Trigo-Stockli et al. 1995; Krysinska-
Traczyk et al. 2001; Bakutis et al. 2006;Gonzálezet
al. 2008). The other fungal species belonging to genera
Absidia, Aspergillus,Bipolaris/Drechslera, Cladospo-
rium, Cephalosporium, Chaetomium, Epicoccum,
Oidiodendron, Penicillium,Rhizoctonia,Rhizopus,
Stemphyllium and Trichothecium have not been always
determined, and even if they have occurred they
used to have a different status, because sometimes
they have been dominant and sometimes they have
occurred occasionally (Trigo-Stockli et al. 1995;
Krysinska-Traczyk et al. 2001; Bakutis et al. 2006;
Fakhrunnisa et al. 2006).
Many species of the genus Fusarium have been
isolated worldwide from wheat kernels (Muthomi et
al. 2008; González et al. 2008; Oerkea et al. 2010;
Spanic et al. 2010). F. graminearum (Trigo-Stockli et
al. 1995) or the combination of this species with F.
poae (Ioos et al. 2004; Xu et al. 2005; González et al.
2008; Oerkea et al. 2010; Spanic et al. 2010) have
been most often identified. Ioos et al. (2004)have
clearly identified the increasing importance of F. gra-
minearum and F. poae in the FEB complex in Europe.
In Serbia, the most important pathogenic species
associated with wheat, barley and maize is F. grami-
nearum. Furthermore, F. poae also is the most impor-
tant pathogenic species for wheat and barely, while
species of the section Liseola (F. verticillioides,F.
subglutinans and F. proliferatum) are more important
for maize and sorghum (Levićet al. 2009). The pre-
cipitation in Serbia during the wheat flowering time in
recent decades has been of a local character and has
had a significant effect on a variation of the intensity
of the spike infestation with fusarioses and Fusarium
head blight (FHB). In such a way, the grain yield
reduction varied from 3.5 to 38.3 %, depending on
agroecological conditions of the cultivation and resis-
tance of wheat varieties (Levićet al. 2008a).
The aim of this study was to examine mycobiota,
especially species of the genus Fusarium, and to de-
termine whether there was interdependence in their
occurrence on rachides and kernels of wheat.
Materials and methods
Field sampling
Thirty one field sites in 19 growing locations where 14
bread wheat varieties were grown were chosen mostly
in the northern part of Serbia. Mature heads were hand
collected from four sites each of 0.25 m
from each
field. The samples were packed in paper bags and
immediately sent to the laboratory. The heads were
manually threshed. Samples contained, on the aver-
age, 630 rachides and 725.1 g kernels. The kernel
moisture ranged from 11.1 to 13.2 %. The samples
were stored at 5±1°C until analysed. Field sampling
was done in cooperation with the Extension Services
across Serbia.
Analysis of field samples
The rachis and kernel samples were rinsed under tap
water for an hour and then were surface-sterilised by
incubating for 1 min in 1 % (v/v) sodium hypochlorite
solution and rinsed three times with distilled water.
They were then dried, and one rachis or eight kernels
were transferred onto 2 % water agar (WA) and incu-
bated under ambient conditions, 25±2°C and daylight.
Six to seven days after incubation, samples were ex-
amined under a low magnification stereomicroscope.
In order to determine species such as Chaetomium
spp., Sordaria spp. and Thielaviopsis spp., incubated
samples were once again examined after 57 days.
The mycelia of Fusarium species growing out of the
rachides or kernels were transferred to potato dextrose
agar (PDA) and carnation leaf agar (CLA) under sterile
conditions to obtain pure cultures for the morphological
identification of species according to Burgess et al.
(1994). Subcultures on PDA were incubated in the dark
at 25°C, while those on CLA were incubated at 12 h
light (combined fluorescent and NUV light)/dark
250 Eur J Plant Pathol (2012) 134:249256
regime. All mentioned media were prepared according
to procedures described by Burgess et al. (1994). Forty
rachides and 128 kernels of each sample were analysed
in four replications.
Statistical analysis
The prevalence of fungi was expressed as the percent-
age of infected samples (isolation frequency) and the
infection levels as the percentage of infected kernels
(isolation incidence).
The isolation frequency (F) and the incidence (I) of
fungus were estimated as follows (Ghiasian et al. 2004):
F(%)0[Number of samples in which a species oc-
curred/Total number of samples] x 100; and I (%)0
[Number of rachides/kernels in which a species oc-
curred/Total number of rachides or kernels] x 100. The
distribution of the infection levels in five frequency
classes was performed according to Ioos et al. (2004).
The interrelation of the fungal species on rachides
and kernels were determined by the Pearson Product
moment Correlation. The median value of the incidence
of F. graminearum and Alternaria spp. in rachides and
kernels of different wheat varieties in various environ-
ments in Serbia was calculated using Microsoft Office
Excel 2007.
Fungal enumeration
Out of 31 surface-disinfected wheat samples, 30 and
nine fungal genera were isolated and identified from
rachides and from kernels, respectively (Table 1).
Phoma spp. was the only species that was not isolated
from the rachides, but was isolated from kernels.
Species of the genera Fusarium,Alternaria,Chaeto-
mium and Bipolaris were determined in 100 %, 96.8 %,
90.3 % and 61.3 % rachis samples, respectively, with the
incidence of 39.0 (±21.7), 87.0 (±8.8), 18.1 (±18.3) and
6.7 (±6.8) percentages, respectively (Table 1). The most
often identified species of the genus Bipolaris was B.
sorokiniana, and much less B. tetramera and others. The
distribution of the infection levels of other fungal species
was within the frequency range of >5 to 10 (Epicoccum
spp., Aspergillus spp., Paecylomices spp., Sordaria spp.,
Sporotrix spp., Thielaviopsis spp., Microdochium spp.,
Mucor spp. and Papulospora spp.), and of >10 to 25
(Acremoniella atra,Gonatobotrys spp., Nigrospora ory-
zae,Rhizopus spp., Trichoderama spp., Cladosporium
spp., Cephalosporium spp. and Penicillium spp.).
Out of fungi identified on wheat kernels, species of
the genera Fusarium and Alternaria were the most
frequent (100 %) with the incidence of 22.0 (±18.2)
and 48.5 (±21.5) percentages, respectively (Table 1).
One species was in the class within a frequency range
of >5 % to 10 % (Phoma spp.), five species within
the range of >10 % to 25 % (Cephalosporium spp.,
Bipolaris spp., Cladosporium spp., Epicoccum spp.
and Nigrospora oryzae), while the frequency of Chae-
tomium spp. was over 25 %.
Twelve and 11 species of the genus Fusarium were
identified on rachides and kernels, respectively (Table 2).
On the average, Fusarium species were more frequent on
rachides (mean 24.0 %) than on kernels (mean 15.2 %).
F. chlamydosporum,F. oxysporum and F. solani were
detected only on rachides, while F. arthrosporioides and
F. avenaceum were determined only on kernels. The
remaining Fusarium species were recorded on both,
rachides and kernels.
F. graminearum was detected in 30 out of 31 sam-
ples (in 96.8 % cases) on both, rachides and kernels.
The incidence of this species on rachides and kernels
were almost the same (24.0 % vs. 22.0 %).
F. poae was the second most prevalent Fusarium
species on both, rachides (93.5 %) and kernels
(51.6 %). However, the difference in the incidence of
this species on rachides and kernels was significant:
11.6 (±9.1) and 1.8 (± 1.4) percentages, respectively
(Table 2). Furthermore, F. sporotrichiodes was more
frequent on rachides (16.1 %) than on kernels (6.5 %).
A very high frequency of species of the section
Liseola was determined on rachides. This was partic-
ularly attributed to F. verticillioides (64.5 %). F. pro-
liferatum and F. subglutinans were detected on
rachides in 12.9 % and 9.8 % of samples, respectively
(Table 2). The most often isolated species of this
section from grain was F. verticillioides (19.4 %),
while F. proliferatum and F. subglutinans were
detected in 9.7 % of samples. The incidence of these
fungi on kernels amounted to 1.7 (±1.1), 3.1 (±4.0)
and 1.4 (±0.7) percentages, respectively.
The distribution of the infection levels of Fusarium
species on rachis samples was in the classes within a
frequency range of >5 to 10 (F. chlamydosporum,F.
equiseti,F. semitectum,F. solani,F. subglutinans and
F. tricinctum), and >10 to 25 (F. oxysporum and F.
Eur J Plant Pathol (2012) 134:249256 251
sporotrichiodes), while on kernels they were distrib-
uted only in one frequency class (>5 to 10).
Fungal relationships
The positive correlation was determined for the fre-
quency and incidence of fungi in both, rachides (r0
0.6191**) and kernels (r00.8524**). Furthermore,
there was also a positive correlation (r00.8074**)
between the incidences of fungi on rachides and ker-
nels, as well as, between the incidences of fungi in all
samples (r00.9584**).
The isolation incidence of F. g r a m i n e a r u m and
Alternaria spp. in rachides and kernels of different
wheat varieties in diverse environments in Serbia is
presented in Table 3. The positive correlation was
established between frequencies of F. graminearum
on rachides and kernels (r 00.5356**), while this cor-
relation, although positive, was not statistically signif-
icant for Alternaria spp. (r00.1729). The correlation
between frequencies of F. graminearum and Alterna-
ria spp. was negative on both, rachides (r00.3783*)
and kernels (r00.4863**).
Generally, greater abundance of different fungal spe-
cies was determined in rachis samples than in kernel
samples of the 14 wheat cultivars grown under diverse
agroecological conditions (19 locations). However,
differences between rachis and kernel mycobiota re-
lated to the frequency and incidence of certain species
of the genus Fusarium are much smaller.
Table 1 Frequency and incidence of fungi on wheat rachides and kernels
Species isolated Rachides Kernels
Frequency (%) Incidence (%) Frequency(%) Incidence (%)
Range Mean± SD Range Mean± SD
Acremoniella atra 19.4 3.112.5 4.7 (± 2.3) 0.0 0.0 0.0
Alternaria spp. 96.8 68.8100.0 87.0 (±8.8) 100.0 9.886.7 48.5 (±21.5)
Aspergillus spp. 6.5 3.1 3.1 (±0.0) 0.0 0.0 0.0
Bipolaris spp. 61.3 2.525.0 6.7 (±6.8) 22.6 0.8 0.8 (±0.0)
Cephalosporium spp. 13.4 3.192.5 26.1 (±37.4) 22.6 0.82.3 1.0 (±0.6)
Chaetomium spp. 90.3 3.178.1 18.1 (±18.3) 32.3 1.620.3 7.2 (±6.4)
Cladosporium spp. 19.4 2.59.4 4.6 (±2.7) 19.4 0.83.9 2.0 (±1.3)
Epicoccum spp. 9.7 3.118.8 11.5 (±7.9) 12.9 0.81.6 1.2 (±0.5)
Fusarium spp. 100.0 3.190.0 39.0 (±21.7) 100.0 0.855.5 22.0 (±18.2)
Gonatobotrys spp. 12.9 3.1 3.1 (±0.0) 0.0 0.0 0.0
Microdochium spp. 3.2 3.1 3.1 0.0 0.0 0.0
Mucor spp. 3.2 3.1 3.1 0.0 0.0 0.0
Nigrospora oryzae 12.9 3.118.8 8.6 (±7.4) 16.1 0.84.7 2.4 (±.8)
Paecylomices spp. 6.5 2.53.1 2.8 (±0.4) 0.0 0.0 0.0
Papulospora spp. 3.2 18.8 18.8 0.0 0.0 0.0
Penicillium spp. 16.1 2.59.4 4.9 (±2.9) 0.0 0.0 0.0
Phoma spp. 0.0 0.0 0.0 9.8 0.81.6 1.3 (±0.5)
Rhizopus spp. 12.9 2.56.3 3.8 (±1.7) 0.0 0.0 0.0
Sordaria spp. 6.5 2.55.0 3.8 (±1.8) 0.0 0.0 0.0
Sporotrix spp. 6.5 3.16.3 4.7 (±2.3) 0.0 0.0 0.0
Thielaviopsis spp. 6.5 27.5 27.5 (±0.0) 0.0 0.0 0.0
Trichoderama spp. 12.9 3.1 3.1 (±0.0) 0.0 0.0 0.0
Ulocladium spp. 22.6 3.115.6 6.2 (±5.4) 0.0 0.0 0.0
252 Eur J Plant Pathol (2012) 134:249256
The positive correlation established between infec-
tions of rachides and kernels caused by F. graminearum,
has a scientific explanation. During the plant infection,
F. graminearum spreads by systemic growth through the
rachis from one spike to another (Ribichich et al. 2000;
Wanj i r u e t a l . 2002). Histopathological studies showed
that the colonisation of wheat heads by F. graminearum
occurred in two ways, either by a horizontal or by a
vertical path (Ribichich et al. 2000). In the horizontal
path, the fungus invaded anthers and bracts of contigu-
ous florets in the first spikelet invaded, then moved
through the rachis and the rachilla to the contiguous
spikelet. In the vertical path, the fungus moved
through vascular bundles and parenchyma to invade
spikelets above and below the originally infected
spikelet. At later stages of infection, the pathogen
switched from predominately vertical to lateral growth
and accumulated below the surface of the rachis
(Brown et al. 2010). Delayed hyphal colonisation of
the vascular bundles in the rachis was observed in the
type II resistant genotypes (Foroud and Eudes 2009).
Transmission electron microscope studies showed that
at 5 days after inoculation, the hyphae had reached
the rachis from the infected ovary, lemma and palea
(Wanjiru et al. 2002). The fungus extended inter- and
intracellularly in the cortical tissue and vascular bun-
dles of the rachis.
Jansen et al. (2005) found that hyphae of F. g r a m i -
nearum reaching the rachis proceeded to apicallylocated
developing kernels. In the absence of trichothecenes, the
fungus is blocked by the development of heavy cell wall
thickenings in the rachis node of wheat, a defence
inhibited by the mycotoxin. In barley, hyphae of both
wild-type and trichothecene knockout mutant are
inhibited at the rachis node and rachilla, limiting infec-
tion of adjacent florets through the phloem and along the
surface of the rachis.
According to the literature more studies have
been conducted on kernel mycobiota than on rachis
mycobiota. Brandfass and Karlovsky (2006)have
stated that the only Fusarium species found apart
from F. graminearum and F. culmorum was F. poae,
occurring just in three instances in rachides, which
also contained F. graminearum or F. culmorum, and
in four instances in rachides where none of the other
two Fusarium spp. were detected. Other fungal spe-
cies occasionally recovered from the rachides were
Alternaria spp., Rhizoctonia cerealis and Epicoccum
spp. In comparison with these results, our results show
that a significantly higher number of fungi (22 fungal
Table 2 Frequency and incidence of the Fusarium species on rachides and kernels of wheat
Species Rachides Kernels
Frequency (%) Incidence (%) Frequency (%) Incidence (%)
Range Mean±SD Range Mean±SD
F. arthrosporioides 0.0 0.0 0.0 3.1 0.8 0.8
F. avenaceum 0.0 0.0 0.0 3.1 0.8 0.8
F. chlaydosporum 3.1 3.1 3.1 0.0 0.0 0.0
F. equiseti 6.5 5.010.0 7.5 (±3.5) 6.5 0.81.6 1.2 (±0.6)
F. graminearum 96.8 3.190.0 24.0 (±20.5) 96.8 1.667.2 22.0 (±18.2)
F. oxysporum 16.1 3.125.0 8.5 (±9.3) 0.0 0.0 0.0
F. poae 93.5 3.128.1 11.6 (±9.1) 51.6 0.86.3 1.8 (1.4)
F. proliferatum 12.9 2.56.4 3.8 (±1.8) 9.7 0.87.8 3.1 (±4.0)
F. semitectum 6.5 3.16.3 4.7 (±2.3) 3.1 0.8 0.8
F. solani 3.1 6.4 6.4 0.0 0.0 0.0
F. sporotrichiodes 16.1 3.15.0 3.4(±1.0) 6.5 0.8 0.8 (±0.0)
F. subglutinans 9.8 3.13.2 3.1 (±0.1) 9.7 0.82.3 1.4 (±0.7)
F. tricinctum 6.5 6.37.5 6.9 (±0.8) 3.2 2.3 2.3
F. verticillioides 64.5 3.128.1 7.8 (±6.1) 19.4 0.83.1 1.7 (±1.1)
Mean 24.0 15.2
Eur J Plant Pathol (2012) 134:249256 253
genera) were determined on wheat rachides and that
the genera Fusarium,Alternaria,Chaetomium and Bipo-
laris were dominant. Out of 11 species of the genus
Fusarium, F. graminearum (96.8 %) and F. poae
(93.5 %) had the highest incidence, while F. c u l m o r u m
was not detected.
It should be mentioned that the frequency of the
Fusarium species of the section Liseola (F. verticillioides,
F. proliferatum and F. subglutinans) was relatively high
on rachides and kernels of wheat. Recent literature data
has been indicating the importance of these species in the
aetiology of diseases of wheat kernels and contamination
by mycotoxins. Desjardins et al. (2006)characterised
nine F. proliferatum strains from wheat from Nepal
for ability to cause wheat kernel black point under
greenhouse conditions, and for fumonisin contamina-
tion of infected kernels. According to Stankovićet al.
(2012) a large number of stored wheat kernel samples
Table 3 Incidence of isolated F. graminearum and Alternaria spp. in rachides and kernels of different wheat varieties in diverse
environments in Serbia
No. of samples Wheat cultivars Locations F. graminearum Alternaria spp.
Rachides Kernels Rachides Kernels
224 Dragana Pirot 3.1 8.6 96.9 53.1
223 Dragana Zobnatica 15.6 2.3 81.3 54.7
208 Evropa Bač12.5 10.9 81.3 41.4
167 Evropa Gredetin 3.1 3.1 81.3 21.1
216 Evropa Krsmanovo 34.3 25.8 82.5 55.5
164 Evropa Sombor 22.5 7.8 75.0 39.8
172 Evropa 90 Kikinda 30.0 1.6 100.0 40.6
169 Evropa 90 L. Šor 3.1 14.1 90.6 74.2
162 Evropa 90 Sombor 6.3 12.5 78.1 53.1
212 Evropa 90 V. Radinci 15.6 14.1 84.4 84.4
220 Kg 20 Zobnatica 6.4 8.59 93.8 55.5
207 Kragujevčanka Zemun 18.8 55.5 87.5 25.8
210 Mina B. Petrovac 12.5 27.3 96.9 66.4
151 Pahulja Zemun Polje 3.1 2.34 93.8 84.4
222 Pesma Zobnatica 15.6 14.1 81.3 61.7
175 Pobeda Kovin 40.6 46.9 93.8 51.6
213 Pobeda N. Pazova 21.9 13.3 84.4 25.8
214 Pobeda S. Banovci 25.0 28.1 100.0 32.1
215 Pobeda S. Mitrovica 43.8 20.3 75.0 36.7
150 Pobeda Zemun Polje 43.8 27.3 100.0 50.0
219 Renesansa Despotovo 0.0 0.0 87.5 73.4
174 Renesansa Kikinda 37.5 19.5 81.3 55.5
209 Renesansa R. Šančevi 12.5 9.4 78.1 86.7
163 Renesansa Sombor 9.4 28.9 68.8 39.1
211 Renesansa V. Radinci 71.9 40.6 75.0 51.6
155 Renesansa Zemun Polje 90 67.2 87.5 17.2
217 Renesansa Zobnatica 18.8 1.6 96.8 84.4
165 Simonida Loznica 43.8 7.0 80.7 23.4
153 Takovčanka Zemun Polje 6.3 43.8 90.6 25.8
154 Tritikale Zemun Polje 34.4 51.6 96.9 28.1
152 Žitka Zemun Polje 18.8 46.1 75.0 9.8
18.8 14.1 84.4 51.6
254 Eur J Plant Pathol (2012) 134:249256
(53.164.0 %) contained FB
at levels higher than
1,000 mg kg
Our studies confirmed that in Serbia, as well as, in
Europe (Ioos et al. 2004), F. graminearum and F. poae
were the most frequent species in the FEB complex.
Our previous studies show that under agroecological
conditions of Serbia, F. graminearum mainly devel-
oped along the rachides (Levićet al. 2008a). These
points out that cultivated varieties of wheat are not the
type II resistant or resistant to spreading of pathogens
on spikes. On the other hand, F. poae was the most
often developed on the rachis tips, and although it was
very frequent it did not express pathogenic properties
against wheat seedlings (Levićet al. 2008b).
Unlike F. graminearum and F. poae, other species
of the genus Fusarium did not spread beyond kernels
(F. arthrosporioides and F. avenaceum) or rachides (F.
chlamydosporum,F. oxysporum and F. solani). These
results point out to smaller effects of these Fusarium
species on the development of FHB.
Different incidences of F. graminearum on wheat
kernels were established in dependence on the location
in Serbia in which the varieties were grown. For
example, the incidence of this species in kernels of
the variety cv-10 varied from 0 % to 71.9 % over
seven locations. These differences can be explained
by different impacts of agrometeorological conditions
on the development of spike infection, as well as, by
the application of fungicides. We have previously
determined that precipitation during the stage of wheat
flowering varied over locations and significantly
affected the variation of the incidence of Fusarium
head blight over the environments in Serbia (Levićet
al. 2008a). For the particular years, the climatic
conditions reported by Ioos et al. (2004) were quite
favourable for FHB development with high levels of
moisture at the cereal flowering stage.
Our results are in accordance with results obtained by
other researchers who have studied FHB and deter-
mined a great variation in the species composition and
in dominant species in the fungal complex that caused
FHB. This variation related not only totheir year-to-year
variation (Ioos et al. 2004) or variations in previous
decade (Tomczak et al. 2002), but also to region-to-
region variation (Xu et al. 2005) or zone-to-zone varia-
tion (Muthomi et al. 2008), and also to their field-to-
field variation or even within-field variation (Birzele et
al. 2002; Oerkea et al. 2010). Results obtained in eastern
Croatia, located eastwards from the northern part of
Serbia, differed in frequencies of certain Fusarium spe-
cies in comparison with our results, although the spatial
distance between the two countries is small.
The results of Kosaik et al. (2004) indicated a nega-
tive interaction between F. graminearum and Alternaria
spp. in Norwegian grains, as well as, between F. grami-
nearum and other Fusarium spp. Our results, related to a
negative interaction between F. graminearum and Alter-
naria spp. (r00.4863**), are in accordance with
results gained by these authors. Moreover, we have also
determined a negative interaction between these two
species in rachides (r00.3783*).
In conclusion, the majority of rachis samples
contained more notable quantities of fungal species
than kernel samples of wheat collected from 19 loca-
tions in Serbia characterised with different agroeco-
logical conditions. But, the number of Fusarium
species was approximately the same on rachides and
kernels. The high frequency and incidence of F. gra-
minearum,F. poae and Alternaria species in wheat is a
matter of concern for wheat production.
Acknowledgments The study was a part of investigations
realised within the scope of the Project No. TR-31023 finan-
cially supported by the Ministry of Science and Technological
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... and other fungal species, e.g. Fusarium culmorum, Botrytis cinerea and Cladosporium herbarum (Kilic et al. 2010;Lević et al. 2012;Liggitt et al. 1997;Nicolaisen et al. 2014). A consequence of the non-significant relationship and antagonistic spatio-temporal pattern between A. alternata and Alternaria spp. ...
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Alternaria is a plant pathogen and human allergen. Alternaria alternata is one of the most abundant fungal spores in the air. The purpose of this study was to examine whether Alternaria spp. spore concentrations can be used to predict the abundance and spatio-temporal pattern of A. alternata spores in the air. This was investigated by testing the hypothesis that A. alternata dominates airborne Alternaria spp. spores and varies spatio-temporally. Secondarily, we aimed at investigating the relationship between airborne Alternaria spp. spores and the DNA profile of A. alternata spores between two proximate (~ 7 km apart) sites. These were examined by sampling Alternaria spp. spores using Burkard 7-day and cyclone samplers for the period 2016-2018 at Worcester and Lakeside campuses of the University of Worcester, UK. Daily Alternaria spp. spores from the Burkard traps were identified using optical microscopy whilst A. alternata from the cyclone samples was detected and quantified using quantitative polymerase chain reaction (qPCR). The results showed that either A. alternata or other Alternaria species spores dominate the airborne Alternaria spore concentrations, generally depending on weather conditions. Furthermore, although Alternaria spp. spore concentrations were similar for the two proximate sites, A. alternata spore concentrations significantly varied for those sites and it is highly likely that the airborne samples contained large amounts of small fragments of A. alternata. Overall, the study shows that there is a higher abundance of airborne Alternaria allergen than reported by aerobiological networks and the majority is likely to be from spore and hyphal fragments.
... This genus was detected from almost all sampled wheat fields, with proportions of contamination between 1 and 84%. Other reports of high levels of Alternaria contamination of grain (more than 90% of grains affected) have been from Serbia, Argentina, and Italy (Patriarca et al., 2007;Levic et al., 2012;Ramires et Somma et al., 2019). The results from the present study contradict those of Joubrane et al. (2011) for Lebanon, in which Alternaria species were rarely isolated (frequency of approx. ...
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Alternaria is a ubiquitous genus that may infect wheat in many countries, causing the disease black point. The present study aimed to assess contamination by fungi, of durum wheat kernels from Lebanon, and identify the main Alternaria species contaminants. Alternaria was detected in the majority (97%) of the inspected fields. Contamination by Alternaria differed among the samples according to their geographical origins. The greatest contamination was detected in the West Bekaa area (average 59%), followed by Akkar (55%), and lowest was observed in Baalbeck (2%). HPLC-DAD analyses performed on grain samples showed that altenuene, alternariol, alternariol monomethyl ether, and tenuazonic acid were not detected in any sample. Phylogenetic analyses, based on DNA sequences of β-tubulin, glyceraldehyde-3-phosphate dehydrogenase and calmodulin gene fragments, showed that Alternaria field strains belonged to two major sections: Alternaria (51%) and Infectoriae (40%). The remaining strains were in separate clades in sections Ulocladioides (3%), Chalastospora (3%) and Pseudoalternaria (3%). Although this study revealed no contamination of wheat kernels by Alternaria mycotoxins, the potential risk of mycotoxin accumulation remains high due to the widespread occurrence of toxigenic Alternaria species on kernels.
... Fusarium head blight (FHB) is one of the most devastating diseases of small grain cereals worldwide and, in Serbia, it is mainly caused by Fusarium graminearum Schwabe (sexual stage Gibberella zeae (Schwein.) Petch) (Lević et al., 2012). The main goals of breeding programs are to obtain FHB-resistance varieties as well as improve yield and quality of cereal crops. ...
... In our study, metabarcoding also revealed the presence of two common saprophytes, Epicoccum (OTU 2) and Cladosporium (OTU 5), that did not appear to be associated with gluten strength. Epicoccum nigrum (syn E. purpurascens), a common saprophyte on seeds and other plant materials, is reported from many studies of fungi on wheat seed (Lević et al., 2012;Nicolaisen et al., 2014;Overaa, 1978;Ylimaki, 1981) and was one of the most abundant species in our study. This fungus has been investigated for antagonistic activity against fungal pathogens, including F. graminearum Ogórek and Plaskowska, 2011). ...
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The bread-making quality of wheat depends on the viscoelastic properties of the dough in which gluten proteins play an important role. The quality of gluten proteins is influenced by the genetics of the different wheat varieties and environmental factors. Occasionally, a near complete loss of gluten strength, measured as the maximum resistance towards stretching (Rmax), is observed in grain lots of Norwegian wheat. It is hypothesized that the loss of gluten quality is caused by degradation of gluten proteins by fungal proteases. To identify fungi associated with loss of gluten strength, samples from a selection of wheat grain lots with weak gluten (n = 10, Rmax < 0.3 N) and strong gluten (n = 10, Rmax ≥ 0.6 N) was analyzed for the abundance of fungal operational taxonomic units (OTUs) using DNA metabarcoding of the nuclear ribosomal Internal Transcribed Spacer (ITS) region ITS1. The DNA quantities for a selection of fungal pathogens of wheat, and the total amount of fungal DNA, were analyzed by quantitative PCR (qPCR). The mean level of total fungal DNA was higher in grain samples with weak gluten compared to grain samples with strong gluten. Heightened quantities of DNA from fungi within the Fusarium Head Blight (FHB) complex, i.e. Fusarium avenaceum, Fusarium graminearum, Microdochium majus, and Microdochium nivale, were observed in grain samples with weak gluten compared to those with strong gluten. Microdochium majus was the dominant fungus in the samples with weak gluten. Stepwise regression modeling based on different wheat quality parameters, qPCR data, and the 35 most common OTUs revealed a significant negative association between gluten strength and three OTUs, of which the OTU identified as M. majus was the most abundant. The same analysis also revealed a significant negative relationship between gluten strength and F. avenaceum detected by qPCR, although the DNA levels of this fungus were low compared to those of M. majus. In vitro growth rate studies of a selection of FHB species showed that all the tested isolates were able to grow with gluten as a sole nitrogen source. In addition, proteins secreted by these fungi in liquid cultures were able to hydrolyze gluten substrate proteins in zymograms, confirming their capacity to secrete gluten-degrading proteases. The identification of fungi with potential to influence gluten quality can enable the development of strategies to minimize future problems with gluten strength in food-grade wheat.
... In addition, G. graminis (1.1%) and Pseudocercosporella herpotrichoides (0.7%) were present at low levels. Until now, there were no reports on which Fusarium species predominates as causal agent of FRR and FCR in Serbia, although it was reported that F. graminearum predominates as causal agent of FHB (Lević et al., 2012). In addition, Serbia is facing with increment of frequency, intensity, and duration of periods with extreme climatic conditions which were reported to be climate change manifestations worldwide (Westra et al., 2014). ...
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Investigations related with factors influencing root and crown rot are rare and mainly related to farming practice and soil management. The main objective of this study was to examine broader range of factors influencing stem-base infestation of winter wheat in the field conditions. The effect of spatial distribution of infected plants on disease index (DIs) assessments was also investigated. Analysis of factors influencing DIs of crown rot of wheat demonstrated significant influence of the growing seasons (P < 0.001) and extreme fluctuations in winter temperatures (P < 0.001). In addition to that, localities together with their interaction with the growing season also significantly influenced DIs (P < 0.001). Aggregation of infected plants influenced variability of DI estimations, and it was pointed out that more extensive investigation should be conducted on broad range of DI in order to establish sampling method giving uniform sampling precision. Fusarium graminearum was shown to be predominant Fusarium species in Serbia (72.6%) using sequence-characterized amplified region analysis. Interestingly F. oxysporum was isolated in higher frequencies (27.4%) than it was reported in the literature. Given that there were no reports on the diversity of Fusarium species causing crown rot of wheat in Serbia, this study presents first report on this important subject. It also indicated that more attention should be focused on combined effects of abiotic and biotic factors influencing stem-base infestation of winter wheat. This knowledge will contribute to better understanding of factors influencing root and crown rot of wheat which would ensure sustainable disease management in the future.
... Although identified Although the mycobiota of the genus Cladosporium had a high frequency (80.0%), their incidence was rather low (7.7%) on the common wheat (Table 1). Representatives of this genus, together with Nigrospora oryzae, are common mycobiota of wheat grain all over the world (Fahrunnisa et al., 2006;Lević et al., 2012b). ...
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The incidence of mycobiota on common wheat (Triticum aestivum) and spelt (Triticum aestivum ssp. spelta) samples, collected during the harvest in 2015, was investigated. The obtained results showed that more genera of mycobiota were isolated from the common wheat grains than from the spelt grains. The most frequently isolated species from common wheat grains belonged to genus Alternaria (41.7%), followed by Fusarium (15.2%), while the incidence of this mycobiota on the spelt grains were 32.4% and 10.4%, respectively. Aspergillus flavus was identified in 40.0% wheat samples, with the incidence of 2.0%. Additionally, this study was undertaken in respect of the occurrence and toxigenic potential of A. flavus isolates from these small grain cereals. A simple screening method was applied to determine toxigenic profiles (aflatoxins production) of A. flavus isolates from common wheat. The results revealed the importance of precise investigation of mycobiota distribution on common wheat and spelt grains, and especially the investigation of toxigenic potential of A. flavus.
... Contrary to wheat, where statistically highly significant negative correlation between Fusarium spp. and Alternaria spp. was found (Lević et al., 2012) on maize grains this negative correlation was not statistically significant. ...
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In this study the presence of moulds and mycotoxins in samples of stored maize grains in the period from October 2011 to September 2012 was investigated. Mycological analyses of whole and broken grains showed the presence of species from the genera Alternaria, Aspergillus, Fusarium, Penicillium, Rhizopus and others. Among the Aspergillus and Fusarium genera as potentially toxigenic fungi, Aspergillus flavus was identified with the highest percentage on broken grains (20.38%) whereas F. verticilioides was the predominant species in the whole maize grains (34.04%). In addition, it was obtained that tested samples of stored maize grains were 100% positive with aflatoxin B1 (AFB1), zearalenone (ZON), deoxynivalenol (DON) and fumonisin B1 (FB1) with an average concentration of 1.39 μg kg-1, 71.79 μg kg-1, 128.17 μg kg-1, and 1610.83 μg kg-1, respectively. A significant positive correlation was found between the moisture content and the presence of Fusarium spp. on the broken grains (r = 0.44) and between the moisture content and the concentration of DON (r = 0.61). However, a significant negative correlation was found between moisture content and FB1 (r = -0.34), and between the concentration of ZON and DON mycotoxins (r = -0.58). Key words: moulds, mycotoxins, storage, maize grains
... Opinions of different European scientific committees (BfR 2003;EFSA 2011) recognised the need to collect more information about the toxicity of these substances to understand better the real risk for public health. Several authors from Serbia have stated that the dominant wheat contaminating mycoflora also includes, besides Fusarium genus, the genus Alternaria (Ivanovic et al. 2001;Bagi et al. 2005;Stanković et al. 2007;Lević et al. 2012;Vučković et al. 2012). According to our knowledge regarding the natural contamination of wheat with Alternaria toxins, there are no published data from Serbia. ...
Although Fusarium species remain a main source of mycotoxin contamination of wheat, in recent years, due to the evident climatic changes, other mycotoxigenic fungi have been recognised as important wheat contaminants. Alternaria species, especially Alternaria alternata, have been found as contaminants of wheat as well as wheat-based products. Under favourable conditions Alternaria alternata very often produce alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA) and others Alternaria toxins. The aim of the present study was to examine the presence of three Alternaria toxins (AOH, AME and TeA) in wheat samples harvested during the period of three years (2011-2013). To this end, 92 samples were collected during wheat harvesting from different growing regions of Autonomous Province of Vojvodina, which represents the most important wheat growing area in Serbia. The presence of Alternaria toxins were analysed by HPLC with electrospray ionisation triple quadrupole mass spectrometry (LC-ESI-MS/MS). Among the all analysed wheat samples, 63 (68.5%) were contaminated with TeA, 11 (12.0%) with AOH and 6 (6.5%) with AME. Furthermore, the maximum and mean toxin concentrations were 2676 µg kg(-1), 48.9 µg kg(-1), 70.2 µg kg(-1) and 92.4 µg kg(-1), 18.6 µg kg(-1) and 39.0 µg kg(-1) for TeA, AOH and AME, respectively. Co-occurrence of three Alternaria toxins in wheat samples was detected in six samples, a combination of two toxins was found in two samples and 64 samples contained one toxin. The results showed that among 92 analysed wheat samples only 20 (21.7%) samples were without Alternaria toxins. The presence of Alternaria toxins was also investigated in terms of weather conditions recorded during period of investigation, as well as with the sampling region. This study represents the first preliminary report of natural occurrence of Alternaria toxins in wheat (Triticum aestivum) from Serbia.
Ethiopia is sub-Saharan Africa’s greatest wheat producer. However, its production, productivity and utilisations are constrained by fungal infections, which lead to yield losses and mycotoxin contaminations. The present study was aimed to determined fungal species and multi-mycotoxins in wheat grain samples (n=178) collected during the 2020 cropping season in Ethiopia. Different fungal genera of Alternaria, Aspergillus, Fusarium, Penicillium, and Rhizopus species were isolated from the infected grain samples, of which Fusarium species were abundantly prevalent. Multi-mycotoxin analysis done using liquid chromatography-tandem mass spectrometric (LC-MS/MS). Overall, 49 metabolites of different fungal species including masked, regulated and emerging mycotoxins were detected and categorised into eight groups. Among major mycotoxins and derivatives, deoxynivalenol was frequently detected in about 70.8% of samples with the maximum concertation 15,900 μg/kg, followed by its masked metabolites of deoxynivalenol-3-glucoside detected in 64% of the samples with maximum level 2,120 μg/kg. Among Fusarium metabolites, 15-hydroxyculmorin was detected in 46.6% of wheat samples with maximum level of 4,290 μg/kg, while chrysogin, enniatin B and culmorin were detected in 58.4, 43.3 and 44.9%, of the wheat samples with maximum levels of 154, 325 and 2,860 μg/kg, respectively. Among Alternaria metabolites tenuazonic acid was most prevalent mycotoxin occurring in 79.2% of samples with maximum level (236 μg/kg). Furthermore, metabolites from other fungal genera were detected at different levels. The widespread presence and high amount of multi-mycotoxin in wheat samples indicated proportionately higher exposure levels, which could result in serious food safety and health consequences. Integrating several management strategies both before and after harvest may lower the risk of mycotoxin contamination in wheat, being used as diversified food products in the country.
The interactions among grain-colonizing species on wheat and their effects on incidence and severity of Fusarium head blight are usually neglected in studies. Although saprophytes can predominate over pathogenic species, studies related to the control of saprophytic mycoflora in wheat production are rare. Here we hypothesized that the infection level of Fusarium and contamination level of Alternaria spp. are significantly influenced by environmental factors and their interactions and investigated the relationship between Fusarium and Alternaria spp. under field conditions and estimate its effect on conventional wheat production, The most prevalent species associated with wheat grain were Alternaria spp. (80% in 2012 and 55% in 2013), and the second was F. graminearum (9% in 2012 and 38% in 2013). In general, varieties that are moderately resistant to Fusarium infection are less contaminated with Alternaria spp. compared to susceptible and moderately susceptible varieties. F. graminearum on Alternaria spp. had a strong antagonistic effect on moderately susceptible and susceptible varieties with P < 0.001 using Spearman’s coefficient of correlation. An infection level of F. graminearum over 25% showed antagonistic activity against Alternaria spp. under field conditions. Using prothioconazole + tebuconazole as a chemical measure to prevent F. graminearum infection on susceptible varieties can be related to an increase in the contamination level of Alternaria spp., jeopardizing the effectiveness of seed health control measures.
Full-text available
Fusarium proliferatum is a major cause of maize ear rot and fumonisin contamination and also can cause wheat kernel black point disease. The primary objective of this study was to determine whether nine F. proliferatum strains from wheat from Nepal can cause black point and fumonisin contamination in wheat kernels. For comparison, the study included three Fusarium strains from US maize. In test 1, all the strains but one produced significant symptoms of kernel black point; two strains decreased kernel yield; and four strains contaminated kernels with fumonisins B1, B2 and B3 as determined by liquid chromatography-mass spectroscopy. Strain Ggm202 from Nepal, which produced the highest levels of fumonisins (mean = 49 ug g-1) on five wheat cultivars in test 1, was confirmed to produce fumonisins (mean = 38 ug g-1) on two cultivars in test 2. The data indicate a potential for fumonisin contamination of wheat infected with F. proliferatum.
Understanding variation in pathogen virulence and cultivar resistance is important for development of effective strategies for breeding wheat cultivars resistant to scab. Six isolates of Fusarium graminearum from China and the United States were compared for variation in cultural characteristics and virulence on nine wheat cultivars with different degrees of resistance to scab. The isolates varied in their cultural characteristics and ability to cause scab, but there was no consistent specificity of cultivar resistance or pathogen virulence. Therefore, a mixture of local isolates is an appropriate inoculum to screen for scab resistance. Subculturing the fungus on potato dextrose agar for eight generations did not reduce virulence. In the greenhouse, eight cultivars were tested five times over 3 years by inoculating one central floret in a spike with an Indiana isolate of the fungus. Cultivars Ning 7840, Sumai 49, Fu 5114, and Sumai 3 were consistently resistant. The fungus spread from the inoculated spikelet to noninoculated spikelets of resistant cultivars in less than 20% of the plants, and spread was not evident until 12 days after inoculation. All plants of susceptible cultivar Clark showed spread of infection, and symptoms appeared on noninoculated spikelets by 8 days after inoculation. Sudden blight on the top part of the spike may be an important characteristic of highly susceptible cultivars. Measurement of spread of scab within a spike is a stable and reliable estimate of cultivar resistance.
The natural occurrence of fumonisin B1 (FB1) and its co-occurrence with zearalenone (ZEA), T-2 toxin and deoxynivalenol (DON) were surveyed in 103 winter wheat samples collected after four to six-month storage in family barns from different locations in Serbia. All 103 samples were mycotoxin positive. The mean concentrations of all mycotoxins except ZEA were greater in 2005 than in 2007. FB1 was detected in 82.1% and 92.0% of all samples with ranges of 750-5400 mg kg-1 (mean, 2079.45 mg kg-1) and 750-4900 mg kg-1 (mean 918.76 mg kg-1) in 2005 and 2007, respectively. Moderate positive correlations were found between FB and DON concentrations (r = 0.56 in 2005 and r = 0.54 in 2007) and between FB1 and ZEA concentrations (r = 0.48 in 2005 and r = 0.60 in 2007), while a moderate negative correlation was detected between the production of FB1 and T-2 toxin in 2007 (r = -0.33). This is the first report of FB1 occurrence in naturally-contaminated wheat grain and its simultaneous occurrence with ZEA, DON and T-2 toxin in Serbia. Moreover, this is one of the rare reports presenting the occurrence of FB1 on wheat in the world. Key words: Wheat, Fumonisin B1, Deoxynivalenol, T-2 toxin, Zearalenone
Standard blotter and Deep Freezing methods were used to study the seed-borne mycoflora of 19 samples of wheat, 27 samples of sorghum and 14 samples of barley. A significant contamination with fungal genera was detected in analyzed samples. Fungi most frequently isolated and identified were Absidia sp., Alternaria alternata, Aspergillus sp., A. candidus, A. flavus, A. niger, A.sulphureus, Cephalosprium sp., Chaetomium globosum, Cladosporium herbarum, Curvularia lunata, Drechslera dematioidea, D. halodes, D. hawaiiensis, D. tetramera, Fusarium moniliforme, F. oxysporum, F. pallidoroseum, F. subglutinans, Nigrospora oryzae, Penicillium spp., Piptocephalis sp., Rhizoctonia solani, Rhizopus sp., Stemphylium sp., Syncephalastrum racemosum, Trichoderma hamatum, Trichothecium roseum and Ulocladium sp. This is the first report of Chaetomium globosum and D. hawaiiensis on wheat, A.sulphureus, Fusarium subglutinans, Nigrospora oryzae, Piptocephalis sp., Syncephalastrum racemosum and Trichoderma hamatum on sorghum and A. niger, Cephalosprium sp., Cladosporium herbarum, Drechslera dematioidea, D. tetramera, Trichothecium roseum, Stemphylium sp., and Ulocladium sp., are new records on barley. There does not appear to be any previous report of Absidia sp., Aspergillus sulphureus, Fusarium subglutinans and Rhizoctonia solani on wheat in Pakistan. Deep freezing method showed better results for isolation of Alternaria alternata, Cladosporium herbarum, Drechslera spp., and Fusarium spp.
The spatial pattern of Fusarium-infected kernels and their mycotoxin contamination was studied in four wheat fields in Germany using geo-referenced sampling grids (12–15 × 20–30 m, 28–30 samples per field) at harvest. For each sample, frequency of Fusarium-infected kernels and spectrum of species were assessed microbiologically; mycotoxin contents were determined by HPLC-MS/MS analysis. Spatial variability of pathogens and mycotoxins was analysed using various parameters including Spatial Analysis by Distance IndicEs (sadie® ). Microdochium majus, the most frequent head blight pathogen in 1998, was less frequent in 1999 and could not be detected in kernels from two fields in 2004. Fusarium avenaceum, F. graminearum and F. poae were the most frequent Fusarium species, with 7–8 species per field. The frequency of Fusarium-infected kernels was 3–15% and the incidence of species showed considerable within-field variability. Spatial patterns varied among Fusarium species as well as from field to field. Although pathogens and mycotoxin were often distributed randomly in the field, F. avenaceum, F. graminearum, F. poae, F. sporotrichioides, F. tricinctum and the mycotoxin moniliformin had an aggregated pattern in at least one field. Patterns are discussed in relation to spread of Fusarium species depending on inoculum sources, spore type, kind of dispersal, availability of susceptible host tissue and micro-climate. Sampling of wheat fields for representative assessment of mycotoxins is complicated by random patterns of Fusarium-infected kernels, especially where the frequency of infection is small.
Scab is an important disease of wheat throughout the world: Fusarium graminearum is the species most frequently isolated in Argentina. Histopathological modifications observed in Pro INTA Oasis (a susceptible Argentine cultivar) and in Sumai 3 (a resistant Chinese cultivar) from the time of inoculation, at the spike emergence stage, until major disease expression (10.5 days postinoculation in the susceptible cultivar) are described. Both cultivars showed a horizontal progression of disease, from anthers to glumes, and a vertical progression, from anthers to rachis. Chlorenchyma was the most damaged tissue, with progressive chlorosis and necrosis. Walls of mesophyll, parenchyma, and epidermal cells around the lesions became thicker, particularly in the resistant cultivar. Vessels and sieve tubes were occluded, particularly the former in the susceptible cultivar and the latter in the resistant cultivar. Possible relationships between tissue changes generated during disease progression and known resistance mechanisms are discussed.
Cereal Chem. 72(5):470-474 Wheat samples from various locations in Kansas were tested for mold Kansas. Deoxynivalenol was detected in 23 of 116 samples analyzed invasion by plating on agar medium and then analyzing for the presence (20%) and was correlated highly (r = 0.839, P < 0.001) with the level of of deoxynivalenol, zearalenone, and aflatoxin B 1 using thin-layer chroma- invasion by F graminearum. Zearalenone was detected only in one sam- tography. In eastern Kansas, 29 of 30 samples (96%) were invaded with ple from northeast Kansas. Cool, wet weather during 1993 was an impor- Fusarium graminearum and the mean percentage of invaded kernels was tant factor affecting invasion and toxin formation by E graminearum. 33% in northeast, 16% in east central, and 15% in southeast districts. The The level of mycotoxin in 1993 Kansas wheat was relatively low. highest level of invasion observed was 75% on a sample from northeast Mycotoxins are compounds that are produced by fungi and can cause illness or even death when food or feed containing them are consumed (CAST 1989). Mycotoxins often occur in grain crops in the field before harvest when certain weather conditions prevail. The crop year from July 1992 through June 1993 in Kansas was characterized by above normal total precipitation. For most of the spring and summer of 1993, heavy and frequent rains saturated fields in central and eastern Kansas (Roozeboom 1993). Such unusually high precipitation favors the growth of many fungi, including Fusarium species, that produce toxins. One of the Fusarium species favored by such weather conditions is Fusarium graminearum Schwabe (Gibberella zeae (Schw.) Petch), which causes wheat scab or head blight. Scab results from infection of individual spikelets at or soon after flowering, when they are most susceptible. Infected spikelets are killed, and the fungus then may girdle the rachis so that the head above that point dies. A distinct salmon-pink ring of fungus de- velops at the base of the glumes. Direct yield losses from scab are usually minor but can reach 25-40% in severely diseased fields (Willis 1984). Of greater concern is the ability of the causal fungi to produce deoxynivalenol (vomitoxin), zearalenone, and other toxins.