Relationships of mycobiota on rachides and kernels of wheat

Abstract

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.

Full text

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 (r0−0.3783 *) and
kernels (r0−0.4863 **). 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
Introduction
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) 134:249–256
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
e-mail: jlevic@mrizp.rs
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
2
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 5–7 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) 134:249–256

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.
Results
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) 134:249–256 251

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 (r0−0.3783*)
and kernels (r0−0.4863**).
Discussion
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 3.1–12.5 4.7 (± 2.3) 0.0 0.0 0.0
Alternaria spp. 96.8 68.8–100.0 87.0 (±8.8) 100.0 9.8–86.7 48.5 (±21.5)
Aspergillus spp. 6.5 3.1 3.1 (±0.0) 0.0 0.0 0.0
Bipolaris spp. 61.3 2.5–25.0 6.7 (±6.8) 22.6 0.8 0.8 (±0.0)
Cephalosporium spp. 13.4 3.1–92.5 26.1 (±37.4) 22.6 0.8–2.3 1.0 (±0.6)
Chaetomium spp. 90.3 3.1–78.1 18.1 (±18.3) 32.3 1.6–20.3 7.2 (±6.4)
Cladosporium spp. 19.4 2.5–9.4 4.6 (±2.7) 19.4 0.8–3.9 2.0 (±1.3)
Epicoccum spp. 9.7 3.1–18.8 11.5 (±7.9) 12.9 0.8–1.6 1.2 (±0.5)
Fusarium spp. 100.0 3.1–90.0 39.0 (±21.7) 100.0 0.8–55.5 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 3.1–18.8 8.6 (±7.4) 16.1 0.8–4.7 2.4 (±.8)
Paecylomices spp. 6.5 2.5–3.1 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 2.5–9.4 4.9 (±2.9) 0.0 0.0 0.0
Phoma spp. 0.0 0.0 0.0 9.8 0.8–1.6 1.3 (±0.5)
Rhizopus spp. 12.9 2.5–6.3 3.8 (±1.7) 0.0 0.0 0.0
Sordaria spp. 6.5 2.5–5.0 3.8 (±1.8) 0.0 0.0 0.0
Sporotrix spp. 6.5 3.1–6.3 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 3.1–15.6 6.2 (±5.4) 0.0 0.0 0.0
252 Eur J Plant Pathol (2012) 134:249–256

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 5.0–10.0 7.5 (±3.5) 6.5 0.8–1.6 1.2 (±0.6)
F. graminearum 96.8 3.1–90.0 24.0 (±20.5) 96.8 1.6–67.2 22.0 (±18.2)
F. oxysporum 16.1 3.1–25.0 8.5 (±9.3) 0.0 0.0 0.0
F. poae 93.5 3.1–28.1 11.6 (±9.1) 51.6 0.8–6.3 1.8 (1.4)
F. proliferatum 12.9 2.5–6.4 3.8 (±1.8) 9.7 0.8–7.8 3.1 (±4.0)
F. semitectum 6.5 3.1–6.3 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 3.1–5.0 3.4(±1.0) 6.5 0.8 0.8 (±0.0)
F. subglutinans 9.8 3.1–3.2 3.1 (±0.1) 9.7 0.8–2.3 1.4 (±0.7)
F. tricinctum 6.5 6.3–7.5 6.9 (±0.8) 3.2 2.3 2.3
F. verticillioides 64.5 3.1–28.1 7.8 (±6.1) 19.4 0.8–3.1 1.7 (±1.1)
Mean 24.0 15.2
Eur J Plant Pathol (2012) 134:249–256 253

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
Median
a
18.8 14.1 84.4 51.6
254 Eur J Plant Pathol (2012) 134:249–256

(53.1–64.0 %) contained FB
1
at levels higher than
1,000 mg kg
−1
.
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. (r0−0.4863**), are in accordance with
results gained by these authors. Moreover, we have also
determined a negative interaction between these two
species in rachides (r0−0.3783*).
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
Development of Republic of Serbia.
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