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India is endowed with enormous variability and genetic divergence for cucumber germplams throughout the country. However, several unique indigenous germplasm that could potentially enhance cucumber productivity and nutritional quality, have not yet been wiely utilized in crop improvement programmes due to lack of relevant information. So, there is a great need of screening cucumber germplasm to identify elite genotypes with improved quality and higher yield so that they may be utilized either directly as a selection or as a parent in hybridization programme. Cucumber (Cucumis sativus L.) is known to be highly preferred host for a number of diseases and pests. Among the diseases, downy mildew and virus diseases cause heavy losses particularly during hot and humid season. Downy mildew is one of the most important foliar diseases of cucurbits, causing significant yield losses not only in India but also in the USA, Europe, China and Israel (Thomas 1996). The downy mildew pathogen has a wide geographical distribution and host range of approximately twenty different cucurbitaceous crops (Lebeda and Urban 2007, Palti and Cohen 1980). Downy mildew management relies mainly on the application of fungicides and the use of resistant host. Fungicide resistance of Pseudoperonospora cubensis have been documented throughout the world (Lebeda and Urban 2007, Zhu et al. 2008). Use of resistant germplasm as source in resistance breeding program may be the answer for developing resistant variety to control the disease(s). ABSTRACT The material used in the present study is of diverse nature and can be used in the breeding programme for development of improved genotypes in cucumber (Cucumis sativus L.). The unique accessions identified in this study can be useful as genetic stocks. The superior genotypes for fruit trait variability combined with disease resistance may assist the breeders in identifying populations with desired traits for inclusion in crop improvement programme.
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India is endowed with enormous variability and genetic
divergence for cucumber germplams throughout the country.
However, several unique indigenous germplasm that could
potentially enhance cucumber productivity and nutritional
quality, have not yet been wiely utilized in crop improvement
programmes due to lack of relevant information. So, there
is a great need of screening cucumber germplasm to identify
elite genotypes with improved quality and higher yield so
that they may be utilized either directly as a selection or as
a parent in hybridization programme.
Cucumber (Cucumis sativus L.) is known to be highly
preferred host for a number of diseases and pests. Among
the diseases, downy mildew and virus diseases cause heavy
losses particularly during hot and humid season. Downy
mildew is one of the most important foliar diseases of
cucurbits, causing significant yield losses not only in India
but also in the USA, Europe, China and Israel (Thomas
1996). The downy mildew pathogen has a wide geographical
distribution and host range of approximately twenty different
cucurbitaceous crops (Lebeda and Urban 2007, Palti and
Cohen 1980). Downy mildew management relies mainly
on the application of fungicides and the use of resistant
host. Fungicide resistance of Pseudoperonospora cubensis
have been documented throughout the world (Lebeda and
Urban 2007, Zhu et al. 2008). Use of resistant germplasm
as source in resistance breeding program may be the answer
for developing resistant variety to control the disease(s).
Indian Journal of Agricultural Sciences 85 (2): 234–9, February 2015/Article
Evaluation of cucumber (Cucumis sativus) germplasm for agronomic traits and
disease resistance and estimation of genetic variability
PRAGYA RANJAN1, K K GANGOPADHYAY2, MANAS KUMAR BAG3, ANIRBAN ROY4,
R SRIVASTAVA5, R BHARDWAJ6 and M DUTTA7
National Bureau of Plant Genetic Resources, New Delhi 110 012
Received: 13 April 2014; Revised accepted: 13 November 2014
ABSTRACT
The material used in the present study is of diverse nature and can be used in the breeding programme for
development of improved genotypes in cucumber (Cucumis sativus L.). The unique accessions identified in this
study can be useful as genetic stocks. The superior genotypes for fruit trait variability combined with disease resistance
may assist the breeders in identifying populations with desired traits for inclusion in crop improvement programme.
Key words: Agronomic traits, Cucumber germplasm, Disease resistance, Estimation, Evaluation,
Genetic variability
86
1Senior Scientist (e mail: ruchi_105@rediffmail.com),
2Principal Scientist (e mail: gangopadhyay1@rediffmail.com),
3Senior Scientist (e mail: manas@nbpgr.ernet.in), 4Senior Scientist
(e mail: anirban@nbpgr.ernet.in), 5Senior Scientist (e mail:
rsrivastava@nbpgr.ernet.in), 6Senior Scientist (e mail:
rakesh_bhardwaj@nbpgr.ernet.in), 7Head, GED (e mail:
mdutta@nbpgr.ernet.in)
The assessment of variability present in any crop species
is the essential pre-requisite for planning and execution of
breeding programme for improvement of yield related traits.
The genotypic and phenotypic coefficients of variability
are helpful in exploring the nature of variability in the
breeding populations, whereas estimates of heritability
provides index of transmissibility of characters. The
information on heritability alone may not help in identifying
characters for enforcing selection and heritability estimates
in conjunction with predicted genetic advance is more
reliable (Johnson et al. 1955). Heritability gives the
information on the magnitude of inheritance of characters
from parent to off spring, while genetic advance will be
helpful in finding the actual gain expected under selection.
All these measures are important for the identification of
genetically distant parents to get superior hybrids and
segregants, to evaluate the degree of genetic erosion, or
even to determine the extent of the genetic base of cultivated
forms to develop heterotic groups. Hence, on the basis of
these parameters, suitable selection strategy can be
formulated for higher yield as well as disease resistance in
cucumber. Information on genetic diversity is used to identify
the promising diverse genotypes, which may be used in
further breeding programme. Keeping this in view, the
present study is designed to characterize and evaluate 42
indigenous cucumber accessions including two checks and
to define the level of diversity present among them with
respect to agro-morphological traits and reaction to different
biotic stresses.
MATERIALS AND METHODS
The experimental materials comprised forty two
indigenous collections of cucumber including two checks,
235February 2015]
87
EVALUATION OF CUCUMBER GERMPLASM
conserved in National Gene Bank at National Bureau of
Plant Genetic Resources, New Delhi of which seven
accessions were from Tripura (IC410617, IC410638,
IC410654, IC410657, IC410658A, IC410658B, IC410682),
twenty from West Bengal (IC527391, IC527394, IC527395,
IC527397, IC527400, IC527402, IC527403, IC527404,
IC527405, IC527410, IC527412, IC527413, IC527418,
IC527419, IC527420, IC527423, IC527426, IC527427,
IC527431, IC527434), nine from Uttar Pradesh (IC538121,
IC538126, IC538130, IC538137, IC538145, IC538147,
IC538155, IC538173, IC538186), two from Mizoram
(IC420405, IC420422), one each from Haryana (IC557170)
and Odisha (IC257296) and two checks Pusa Uday and
Pahari Harit.
The present investigation was carried out at Research
Farm of the National Bureau of Plant Genetic Resources,
IARI farm, New Delhi in a Randomized Complete Block
Design with 2 replications for phenotypic evaluation during
kharif season in the year 2011 and 2012. The experimental
site was situated at 28° 35’ N latitude and 77° 12’ E longitudes
with an altitude of 228.6 m above mean sea level. The soil
is sandy loam in texture. The crop was raised in well
prepared hills with a spacing of 60 cm between hills and 4
m between channels. The recommended dose of fertilizer
and agronomic practices were followed to raise a successful
crop. There were seven hills per replication out of which
five plants were selected for taking observation on 14 traits,
viz. node number bearing first female flower, vine length,
number of primary branches, fruit length, fruit diameter,
seed cavity length, seed cavity breadth, fruit weight, number
of fruits/plant, shelf-life, total soluble solids (TSS), seed
length, 100 seed weight and number of seeds/fruit.
Screening of cucumber accessions against the pathogen
causing downy mildew (DM) disease was done following
0 to 9 visual rating scales of Jenkins and Wehner (1983). As
per the Jenkins and Wehner’s scale 0, no disease, immune
(I); 1, few small leaf lesions, highly resistant (HR); 2, few
lesions on few leaves with no stem lesions, resistant (R); 3,
few lesions on few leaves or with superficial stem lesions,
moderately resistant (MR); 4, few well-formed leaf lesions
or superficial stem lesions, moderately susceptible (MS); 5,
few well-formed leaf lesions or enlarging stem lesions,
moderately susceptible (MS); 6, many large leaf lesions or
deep stem lesions with abundant sporulation, or plant more
than 50% defoliated, susceptible (S); 7, many large
coalescing leaf or stem lesions, over 75% of plant area
affected or defoliated, susceptible (S); 8, plants largely
defoliated, leaves or stems with abundant sporulating lesions,
highly susceptible (HS); 9, plants dead, highly susceptible
(HS). Screening for virus disease resistance was followed
with 0-4 scale (0, no symptoms; 1, 1-25% leaf area with
symptoms; 2, 26-50% leaf area with symptoms; 3, 51-75%
leaf area with symptoms; 4, 76-100% leaf area with
symptoms). After scoring, PDI was calculated for each
accession. The accessions were grouped into five categories
on the basis of PDI: 0-10, resistant (R); 11-20, moderately
resistant (MR); 21-30, moderately susceptible (MS); 31-
40, susceptible (S); >40, highly susceptible (HS) (Dhillon
et al. 2007).
Analysis of variance was performed using the GLM
procedure of SAS 9.2 (SAS Institute, 2007). The phenotypic
and genotypic coefficient of variation were calculated
according to Burton and De Vane (1953), heritability, genetic
advance and genetic gain were calculated following Johnson
et al. (1955).
RESULTS AND DISCUSSION
Analysis of variance (Table 1) revealed significant
differences for all the fourteen traits under study. Variance
due to genotypes was highly significant for all the traits
indicating the presence of sufficient variability in the
genotypes selected for this study.
Mean performance of genotypes
Genetic variability is the basic need for a plant breeder
to initiate any breeding programme. Among the horticultural
traits, comparatively wide range was observed for node
number bearing first female flower (4.25-18.95) which
determines the earliness of a variety. It has been observed
that a number of genotypes are having a varying degree of
earliness and lateness (Table 2). The genotypes IC257296,
IC410617, IC410654, IC410657, IC410658B were found
to be the earliest with first female flower at 5th to 6th node
while the genotypes IC420405, IC420422, IC538147 and
IC538155 are found to be very late, i.e. first female flower
at >15th node. Identification of such genotypes would be
useful in extending the availability. Judicious planting of
early and late genotypes will help in sustainable marketing
of cucumber cultivars for a longer period.
Wide range of variations (166.52-227.04 cm, 3.0-9.0)
was observed for vine length and number of primary
branches which are important traits reflecting vegetative
Table 1 Analysis of variance (ANOVA) for horticultural traits of cucumber (pooled data)
Source of df nnff vl (cm) pb fl fd scl scb fw nfp shl TSS sl sw nsf
variance (cm) (cm) (cm) (cm) (g) (days) (0B) (cm) (g)
Replication 1 15.77* 3.52 0.007 4.39* 0.47 2.44* 2.33 250.36 0.01 0.01 0.01 0.003 0.01 702.03
Genotype
41 24.41** 433.88** 3.42** 11.62** 8.47** 1.36** 0.41 3282** 13.26** 1.31** 0.38** 0.08** 0.64** 13583.63**
Error 41 0.763 159.237 0.31 0.697 0.393 0.25 0.265 496.41 0.107 0.04 0.004 0.02 0.02 167.66
Node number bearing first female flower (nnff), vine length (vl), number of primary branch (pb), fruit length (fl), fruit diameter (fd),
seed cavity length (scl), seed cavity breadth (scb), fruit weight (fw), number of fruits/plant (nfp), shelf-life (shl), TSS, seed length (sl),
100 seed weight (sw) and number of seed/fruit (nsf)
236 [Indian Journal of Agricultural Sciences 85 (2)
Table 2 Mean performance of cucumber genotypes for different horticultural traits (pooled data)
Genotypes nnff vl (cm) pb fl fd scl scb fw nfp shl TSS sl Sw nsf
(cm) (cm) (cm) (cm) (g) (days) (0B) (cm) (g)
IC257296 4.25 166.52 5.60 7.88 4.44 6.50 3.55 115.80 14.27 3.95 3.20 0.76 1.84 184.04
IC410617 5.15 177.44 6.10 14.50 3.71 12.45 3.05 136.75 11.40 3.37 4.70 1.39 3.14 315.00
IC410638 16.70 183.96 4.97 14.45 4.22 13.06 2.75 199.65 9.95 2.92 4.90 1.10 2.43 196.00
IC410654 4.95 178.27 5.70 16.60 4.76 13.36 3.23 246.81 12.50 3.92 4.65 1.32 2.66 220.40
IC410657 5.20 188.16 8.00 13.55 5.85 13.26 3.50 166.33 11.60 4.53 3.95 1.10 2.27 259.00
IC410658A 7.50 227.04 6.80 15.41 4.63 13.64 2.75 178.00 13.20 4.23 4.50 1.16 2.53 355.00
IC410658B 5.80 182.90 4.40 10.46 3.78 8.90 2.35 108.50 5.80 3.92 5.07 0.90 1.25 254.00
IC410682 7.55 187.67 8.10 13.46 3.43 10.86 2.85 122.50 11.00 3.97 4.60 1.27 2.63 250.48
IC420405 17.60 175.80 4.60 19.49 7.00 14.60 3.70 202.34 4.75 3.84 4.40 0.72 1.47 54.98
IC420422 18.95 185.25 4.35 14.60 6.01 11.10 3.75 200.60 5.11 3.72 4.80 0.75 1.66 64.32
IC527391 6.95 172.54 4.50 12.48 3.70 8.61 2.80 140.30 8.90 3.52 4.20 1.25 2.51 268.00
IC527394 8.55 180.76 5.90 13.22 4.47 11.73 3.13 134.69 14.00 4.15 4.60 1.10 2.36 379.00
IC527395 9.25 189.18 3.70 11.84 4.61 10.36 3.37 130.63 6.30 3.25 3.60 1.00 2.26 245.00
IC527397 7.80 177.76 3.90 10.27 4.15 8.56 2.83 82.75 6.00 5.48 4.40 1.10 2.56 101.00
IC527400 8.55 208.28 9.30 12.66 3.15 11.56 2.40 88.70 10.00 3.70 4.50 1.14 2.32 251.00
IC527402 9.65 178.16 5.08 13.25 3.97 11.85 3.15 121.50 13.40 4.88 3.50 1.24 3.13 305.00
IC527403 9.60 169.37 4.50 13.53 4.68 12.26 3.40 127.73 7.10 2.97 4.00 1.10 2.54 215.00
IC527404 9.60 224.88 5.60 15.71 4.28 13.42 2.93 170.69 10.20 2.87 4.10 1.14 2.59 210.00
IC527405 11.50 183.06 5.60 13.30 4.28 10.61 2.70 126.06 7.40 4.00 3.90 1.30 3.23 196.00
IC527410 9.85 171.50 4.80 13.09 4.79 12.40 3.18 124.94 14.20 3.37 3.90 1.20 2.99 365.00
IC527412 9.90 203.80 6.00 14.93 4.29 12.23 2.85 139.40 9.80 3.95 4.20 1.10 2.19 350.00
IC527413 10.25 178.32 4.40 14.13 3.60 11.66 2.75 137.25 8.90 4.15 4.10 1.30 3.48 367.00
IC527418 10.50 177.62 3.80 10.35 3.80 8.03 2.75 82.55 9.90 5.15 4.10 1.10 2.83 280.00
IC527419 11.00 198.44 6.60 13.73 3.35 10.48 2.45 88.55 8.50 4.00 4.00 1.12 3.32 198.00
IC527420 10.50 179.58 4.00 10.96 3.80 8.26 2.50 117.00 8.50 7.00 4.20 1.00 2.26 190.00
IC527423 11.50 180.10 4.60 17.36 4.90 14.30 2.95 127.50 12.40 3.92 3.80 1.20 2.58 245.00
IC527426 10.90 168.22 3.00 12.57 3.35 10.28 2.55 125.50 11.30 4.00 5.40 1.00 2.39 279.11
IC527427 10.95 171.46 4.00 10.50 3.45 8.16 2.45 97.80 9.50 4.93 4.40 1.10 2.69 307.00
IC527431 11.50 201.27 6.40 13.03 3.45 9.71 2.47 102.50 5.80 2.20 4.10 1.10 2.47 180.00
IC527434 10.55 178.72 5.00 9.97 3.45 8.52 2.65 92.25 10.50 2.10 4.30 1.00 1.53 395.00
IC538121 12.60 202.74 5.60 14.43 4.15 11.56 3.25 157.38 8.80 4.00 3.90 1.10 2.47 210.00
IC538126 13.49 175.77 4.70 14.08 3.53 12.46 2.52 178.38 9.40 3.87 3.70 0.50 1.54 234.00
IC538130 11.95 172.54 4.10 11.48 4.40 9.33 3.32 93.30 12.40 4.00 3.90 1.10 2.31 210.00
IC538137 13.15 180.62 4.70 12.20 3.88 10.16 2.48 112.10 6.10 3.50 5.00 0.54 1.43 363.00
IC538145 13.85 181.93 5.10 15.20 3.80 12.26 3.33 135.90 10.20 3.90 4.10 1.10 2.26 178.00
IC538147 15.16 171.14 4.30 20.40 4.60 15.33 3.70 226.34 10.00 3.92 4.10 1.10 3.17 230.00
IC538155 15.10 184.28 4.70 14.40 4.15 11.60 2.70 201.00 8.10 4.21 4.20 1.10 3.52 250.10
IC538173 14.50 184.88 3.55 11.69 3.40 9.70 2.75 86.30 10.00 4.10 4.90 1.10 2.59 144.00
IC538186 14.40 182.62 5.10 14.22 3.62 11.60 2.62 132.83 8.82 3.82 4.30 1.10 2.36 130.00
IC557170 14.55 204.00 5.90 15.57 3.75 14.43 2.60 167.98 10.20 3.90 4.40 0.68 1.66 189.00
Pusa Uday 7.20 175.72 5.25 13.87 5.28 12.00 3.42 169.67 9.20 4.02 4.20 0.84 2.43 144.00
Pahari Harit 8.55 217.26 7.40 15.03 5.90 13.33 4.42 145.80 10.00 3.62 4.20 1.20 3.13 176.00
CD (P=0.05) 1.77 25.50 1.13 1.69 1.01 1.27 1.04 45.03 0.66 0.42 0.13 0.11 0.29 26.17
Node number bearing first female flower (nnff), vine length (vl), number of primary branch (pb), fruit length (fl), fruit diameter (fd),
seed cavity length (scl), seed cavity breadth (scb), fruit weight (fw), number of fruits/plant (nfp), shelf-life (shl), TSS, seed length (sl),
100 seed weight (sw) and number of seed/fruit (nsf)
growth (Table 4). IC410658A was found to bear longest
vine (227.04 cm) while IC257296 bear shortest (166.52
cm) vine. Wide variations (7.88- 20.40 cm, 3.15-7.00 cm,
82.55-246.81 g) were observed with respect to fruit length,
breadth and weight respectively, which are considered as
major yield contributing traits. IC538147 (20.4 cm) recorded
the longest fruit and was found at par with IC420405 (19.49
cm) while IC257296 recorded the smallest fruit (7.87 cm).
For slicing cucumber, thin and long fruits are desirable;
however, small fruit types may be desirable for processing
industry. Usually pickling cucumbers are canned as a whole
fruit but slicing cucumber is canned after making slices.
RANJAN ET AL.
88
237February 2015]
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EVALUATION OF CUCUMBER GERMPLASM
The accession showing small fruit may be a good source of
genes for developing small cucumber suitable for processing.
Nevertheless, the small types may also be suitable for
growing in kitchen gardens due to small vine length (166.52
cm).
Quite a good variation was observed with respect to
number of fruits/plant (4.75-14.40), shelf-life (2.1-7.0 days),
seed length (0.50-1.39 cm), 100 seed weight (1.25-3.52 g)
and seed per fruit (54.98-395). IC527426 (14.27), IC527410
(14.2) and IC527394 (14.0) were found to bear significantly
largest number of fruits per vine. Wide variations for
different horticultural traits were earlier reported by Singh
et al. (2002), Das et al. (2003), Verma (2003), Kumar
(2006), Munshi et al. (2007), Hanchinamani et al. (2008),
Yogesh et al. (2009) and Kumar et al. (2013) in cucumber.
All the genotypes under study showed wide variations
for fruit colour (green, light green, dark green and white),
flesh colour (white, green, orange) and total soluble solid
(3.2-5.4° Brix), which decides the consumer’s preference.
Majority of the genotypes including both the check cultivars
had light green coloured fruits which are in general preferred
by consumers. Highest TSS was recorded in IC527426
(5.4°B) followed by IC410658B (5.07°B) and three other
genotypes namely IC410638, IC410617, IC538173
performed better over both the checks (4.2°B) for total
soluble solids. Similar results have also been reported by
Verma (2003) and Kumar (2006) for these characters. Two
accessions, viz. IC420405 and IC420422 were found to
have orange flesh colour. Previously orange flesh cucumber
was reported to be derived from a landrace named
Xishuangbanna Gourd (Cucumis sativus var.
xishuangbannaenensis) from the Prefecture Xishuangbanna
of the Yunnan Province in Southwest China, which is close
to North Eastern part of India and incidentally the above
two orange flesh cucumber were also collected from
Mizoram located in North Eastern part of India. Recent
studies indicated that orange fleshed cucumber of China
(Xishuangbanna gourd) is closely related to Indian cucumber
germplasm (Lv et al. 2012). This suggests that the orange
flesh Indian cucumber germplasm might have migrated to
China from north eastern parts of India, the primary centre
of origin. Hence, there is an urgent need to collect more
diversity for this trait from the north eastern states, and
identify the promising germplasm and use them in breeding
program to develop carotenoid rich cucumber, which might
play a significant role in achieving nutritional security.
Screening for disease resistance
The check varieties Pahari Harit and Pusa Uday both
exhibited susceptible reaction (Score >6) to downy mildew
pathogen indicating presence of high inoculum load in the
experimental area. Out of 38 accesssions screened for disease
reaction, 12 accessions have shown disease symptom
categorised in 0 to 2 score (resistant reaction) and 26
accessions in 4 to 9 score (susceptible reaction) as per 0 to
9 scale during both the year (Table 3). Out of 12 germplasm
showing resistant reaction, three accessions, viz. IC410617,
IC527419 and IC538130 were highly resistant (score = 1).
Wehner and Shetty (1997) evaluated several germplasm in
multiple environments following the Jenkins and Wehner’s
scale (1983) and reported responses of germplasm to downy
mildew as highly resistant having ratings of 1.3 to 3 and as
resistant from 3.3 to 5.0 after analysis. They also classified
some germplasm as resistant if the rating is 1.0 to 5.0, when
evaluated in only two environments. Thirteen accessions
were observed as resistant against virus (PDI= 0 - 10) and
seven accessions were moderately resistant (PDI= 11-20).
Remaining was observed as moderately resistant to highly
susceptible to viruses causing curling, mosaic and severe
stunting diseases. High disease severity of curling and
Table 3 Cucumber germplasm showing disease reaction to downy mildew and virus diseases
Disease reaction Downy mildew Virus diseases
Immune IC410617, IC527419, IC538130 -
Highly Resistant IC410682, IC527391,IC527394, IC527397, IC527400, -
IC527413, IC527418, IC527423, IC538137
Resistant IC527403, IC527404, IC527405, IC527410, IC527412, IC410617, IC410658A, IC410658B, IC410682,
IC527420, IC527431, IC538121, IC538173 IC527394, IC527400, IC527404, IC527410,
IC527431, IC538121, IC538145, IC538155,
IC538186
Moderately Resistant - IC527391, IC527397, IC527402, IC527403,
IC527423, IC538130, IC538173, Pusa Uday (Check)
Moderately Susceptible IC410654, IC410657, IC527426, IC527427,
IC557170, Pahari Harit (Check)
Susceptible IC410658B, IC527402, IC527426, IC527427, IC527405, IC527412, IC527434, IC538126,
IC527434, IC538126, IC538145, IC538147, IC538137, IC538147, IC410638
Pahari Harit (Check), Pusa Uday (Check)
Highly Susceptible IC410654, IC410657, IC410658A, IC527395, IC420405, IC420422, IC527395, IC527413,
IC538155, IC557170, IC538186, IC410638, IC527418, IC527419, IC527420
238 [Indian Journal of Agricultural Sciences 85 (2)
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RANJAN ET AL.
stunting caused by ToLCNDV were observed in 5
accessions. Twelve accessions were identified as resistant
to downy mildew pathogen, 13 accessions resistant to virus.
Incidentally the check Pahari Harit (Score = 6) and Pusa
Uday (Score = 6) exhibited susceptible reaction to downy
mildew pathogen but both have shown resistant reaction to
virus. Three accessions, viz. IC410617, IC527419, and
IC538130 were found free from DM symptom but only
IC410617 was found resistant to virus disease and remaining
two acc. IC527419 and IC538130 were observed as
susceptible to ToLCNDV. Another three acc. IC410682,
IC527394 and IC527400 were highly resistant to DM but
resistant to virus disease, whereas IC527404, IC527410,
IC527431 and IC538121 were resistant to both DM and
virus disease. The accession IC410617, collected from West
Tripura district of Tripura during 2003 had shown immunity
against DM but resistant (R) reaction against ToLCNV.
Besides the resistance to diseases, this novel accession
IC410617 has good agro-morphological characters with
average fruit length of 14.7 cm, diameter (3.7 cm) and fruit
weight (136.7 g). This accession can be utilized as resistant
source to both the diseases.
Coefficients of variability
The estimates of phenotypic and genotypic coefficients
of variation gave a clear picture on the magnitude of variations
presents in the available germplasm (Table 4). High PCV
(>20%) and GCV (>20%) were observed for node number
bearing first female flower, primary branches, fruit weight,
fruits/plant, shelf-life, 100 seed weight, seeds/fruit. High
estimates of PCV and GCV for number of fruits/plant and
fruit weight has been reported earlier in cucumber (Kumar
et al. 2008) and culinary melons (Rakhi and Rajamony
2005). Phenotypic coefficient of variation was higher in
magnitude than genotypic coefficient of variation for all the
characters under study. The high magnitude of variability in
the present study may be due the fact that the genotypes were
collected from different agro climatic conditions. Low GCV
(<10%) was recorded in vine length and seed cavity breadth.
These results are in line with Singh (1997), Yogesh et al.
(2009), Bisht et al. (2010) and Kumar et al. (2013). However,
the difference between PCV and GCV was not higher in all
the characters except vine length, seed cavity breadth and
fruit weight which reflects that the variability existing in
them was mainly due to their genetic makeup. Thus, selection
on the basis of phenotype will be effective.
Heritability and genetic gain
Heritability estimate is an informative parameter to the
breeder for selecting the desired genotypes for further use.
The estimates of heritability were found high (>90%) for
all the characters except primary branch and fruit length
with moderate heritability (80-90%); and vine length, fruit
diameter, seed cavity breadth and fruit weight with low
heritability (<80%) indicating major role of genotypes in
expression of these characters. High heritability estimates
for number of fruits/plant was also reported by Singh (1997),
Munshi et al. (2007) and Bisht et al. (2010). However,
Kumar et al. (2008) and Yogesh et al. (2009) reported high
heritability for fruit length but found moderate heritability
for node number bearing first female flower.
Selection can be exercised on the basis of phenotypic
performance for highly heritable characters. Heritable
variation can be found out with greater degree of accuracy
when heritability is studied in conjunction with genetic
advance. The genetic gain measured in terms of GA as % of
mean, was found high (>50%) for node number bearing
first female flower, fruits/plant and seeds/fruit. Moderate
genetic gain (40-50%) was observed for primary branch,
fruit weight, shelf-life and 100 seed weight. These findings
are in line with Singh (1997), Kumar et al. (2008) and
Yogesh et al. (2009).
Table 4 Estimates of phenotypic and genotypic coefficient of variation, heritability, genetic advance and genetic gain for different
horticultural traits (pooled data)
Character Mean±SE Range GCV PCV Heritability GA GA as %
(%) (%) (bs) of mean
Node number bearing first 10.64±0.62 4.25-18.95 32.31 33.34 0.94 6.01 63.89
female flower
Vine length (cm) 185.23±8.92 166.52-227.04 6.33 9.30 0.46 16.27 8.78
Number of primary branches 5.23±0.39 3.0-9.0 23.86 26.13 0.83 2.56 44.46
Fruit length (cm) 13.57±0.59 7.88-20.4 17.23 18.30 0.89 3.88 33.10
Seed cavity length (cm) 4.23±0.35 3.15-7.0 17.80 18.64 0.91 3.63 34.66
Fruit diameter (cm) 11.3±0.44 6.50-15.33 17.67 21.26 0.69 1.23 29.97
Seed cavity breadth (cm) 2.97±0.36 2.35-4.42 9.35 19.69 0.23 0.28 9.06
Fruit weight (g) 139.11±15.75 82.55-246.81 26.83 31.25 0.74 66.68 46.99
Number of fruits/plant 9.65±0.23 4.75-14.25 26.45 26.66 0.98 6.55 53.51
Shelf-life (days) 3.92±0.15 2.10-7.0 20.32 21.01 0.94 1.57 40.10
TSS (0B) 4.26±0.04 3.20-5.40 10.29 10.40 0.98 0.79 20.77
Seed length (cm) 1.06±0.04 0.50-1.39 18.48 19.15 0.93 0.26 36.39
100 seed weight (g) 2.45±0.1 1.25-3.52 22.73 23.47 0.94 0.79 44.90
Number of seeds/fruit 236.61±9.15 54.98-395.00 34.62 35.05 0.98 130.10 69.75
239February 2015]
91
EVALUATION OF CUCUMBER GERMPLASM
High heritability estimates coupled with high genetic
gain were observed for node number bearing first female
flower, number of fruits/plant and number of seeds/fruit
which reflects that these characters are predominantly
controlled by additive gene effects and more responsive to
selection. Similar results were reported by Kanwar et al.
(2003) for node of first female flower in cucumber; Kumar
et al.(2008) for days to first female flower anthesis, number
of fruits/plant, fruit length and fruit diameter; Devmore et
al. (2010) for fruit weight, number of seeds/fruit, vine
length and fruit number/vine in bitter gourd. High heritability
coupled with moderate genetic gain was observed for fruit
length, seed cavity length, shelf-life and seed length. This
showed that these characters are under non-additive gene
effects and selection for these characters will be less
effective. Such traits are more under the influence of
environment and do not respond to selection. Similar results
for fruit length were reported by Joshi et al. (1981), Kumar
et al. (2008) and Yogesh et al. (2009) and Kumar et al.
(2013).
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... The range varied from 75.25-310.42 g ( Table 2) (2012), Kumar et al. (2013) and Ranjan et al. (2015). The trait recorded moderate phenotypic (24.81) as well as genotypic (23.86) coefficient of variation (Table 10). ...
... These findings are also in accordance with Kumar et al. (2013). However, the results contradict with the findings of Ranjan et al. (2015) who recorded high phenotypic and genotypic coefficient of variation with low heritability and moderate genetic gain. The differences in the result may be due to difference in the experimental material used. ...
... The values ranged from 3.80 -5.38 o B (Table 3) Low phenotypic (9.35) as well as genotypic (6.18) coefficient of variation was recorded in this trait (Table 10). This result contradict the findings of Kumar et al. (2013) and Ranjan et al. (2015), who found moderate estimates for these parameters. Further, in this trait, low heritability (43.64%) and low genetic gain (8.41) were recorded. ...
Thesis
Globally, cucumber (Cucumis sativus L.) is the second most widely cultivated Cucurbit after watermelon. The present investigation entitled “Genetic studies for yield and quality traits in Cucumber (Cucumis sativus L.)” was carried out at Experimental Research Farm, Department of Vegetable Science, Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, (HP) during Kharif, 2015. Thirty genotypes including check variety K-75 were evaluated to ascertain extent of variability, correlation and path coefficient analysis for yield and other horticultural traits along with estimation of genetic divergence among the genotypes. The experiment was laid out in a Randomized Complete Block Design with three replications. Analysis of variance showed significant difference among all the genotypes for all characters under study. Six genotypes namely, LC-2, LC-7, LC-9, LC-10, LC-15 and LC-27 gave sufficiently higher fruit yield, performed better with respect to other horticultural traits and showed lesser severity the diseases viz. angular leaf spot, anthracnose, downy mildew and powdery mildew over the standard check K-75. High estimates of heritability coupled with high genetic gain was depicted for node number bearing first female flower, number of fruits per plant, number of marketable fruits per plant, number of primary branches per plant, hundred seed weight, seed vigour index I, severity of angular leaf spot, severity of anthracnose, severity of downy mildew, severity of powdery mildew, yield per plot and yield per hectare. Yield was significantly and positively correlated with average fruit length, fruit diameter, number of marketable fruits per plant, harvest duration, vine length, number of primary branches per plant, seed length, hundred seed weight, germination percentage, vigour index I and II. Path analysis revealed that harvest duration had maximum positive direct effect on yield followed by vigour index II and marketable fruits per plant. Genetic divergence studies revealed that hybridization between genotypes of cluster II and V will be more rewarding for getting superior progeny(s).
... The results are in consonance with various earlier workers i.e. low GCV was reported for fruit weight and fruit length (Sharma 2017) [25] . In contrary to our findings, low estimates of GCV were reported for vine length (Ranjan et al. 2015 [21] , Pal et al. 2017) [18] and days to anthesis of first female flower (Ahirwar et al. 2018 [27] . Moderate GCV was observed for vine length (Ahirwar et al. 2018). ...
... The results are in consonance with various earlier workers i.e. low GCV was reported for fruit weight and fruit length (Sharma 2017) [25] . In contrary to our findings, low estimates of GCV were reported for vine length (Ranjan et al. 2015 [21] , Pal et al. 2017) [18] and days to anthesis of first female flower (Ahirwar et al. 2018 [27] . Moderate GCV was observed for vine length (Ahirwar et al. 2018). ...
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Temporal changes in the pathogenicity and fungicide resistance of populations of Pseudoperonospora cubensis (cucurbit downy mildew) in the Czech Republic from 2001 to 2003 were observed. Altogether, 152 P. cubensis isolates collected from Cucumis sativus in 10 Czech regions were analysed for pathogenic variation, 74 of which were used for fungicide resistance screening. The data on changes in pathogenicity, as expressed by pathogen pathotypes, exemplified well the process of microevolutionary shift in pathogen populations. During the period studied, there was a considerable increase of pathogenicity that was expressed by a higher complexity of pathotypes and their increasing frequency. However, the diversity of the pathogen populations in general decreased. A similar phenomenon was observed in fungicide (metalaxyl, phosetyl-Al, propamocarb) effectiveness, which varied considerably. Propamocarb was the most effective, but metalaxyl was ineffective and resistance to this fungicide was fixed in the pathogen populations. For phosetyl-Al, there was observed evidence of the start of selection for higher resistance in the P. cubensis populations. It is concluded that P. cubensis could be considered as a population with a high evolutionary potential that is capable of quickly overcoming host resistance and the effectivity of some fungicides. The data are discussed from the viewpoint of integrated crop management.
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