MSc

The research project "Characterization of landraces of ashgourd
[Bcnincasa h ispida (Thunb.) Co gn.]" was carried out at the Department of
Olericulture and the Department of Plant Biotechnology, College of
Agriculture, Vellayani during 2003-2004. The objective of the study was
to catalogue the landraces based on the IBPGR descriptor for cucurbits, to
estimate the genetic parameters for different traits in the germplasm for
identifying superior lines based on yield, quality, pest and disease
resistance and to characterize the landraces using molecular techniques
(RAPD analysis).
Twenty five landraces of Benincasa hispida collected from various
sources upon cataloguing pointed out wide variation for several
morphological characters. Analysis of variance revealed significant
differences among the landraces for all the characters studied namely. vine
length, internodal length, number of primary branches, number of
secondary branches, root shoot length ratio, days to first male flower,
node to first male flower, days to first female flower, node to first female
flower, sex ratio, days to first fruit harvest, fruit length, fruit girth, fruits
per plant, average fruit weight, yield per plant. seeds per fruit, 1000-seed
weight and mosaic incidence.
Among the landraces, BH 15 (Neyattinkara, Thiruvananthapuram)
recorded the maximum yield (21.20 kg), average fruit weight (9.50 kg),
fruit girth (78.05 cm) and 1000-seed weight (96.95 g). Among the
landraces, maximum fruit length was observed for BH 25 (56.00 cm).
BH 22 was the longest in vine length (875.00 cm) and had the highest
number of primary and secondary branches (4.00 and 23.00 respectively).
BH 24 (7.20 cm) was shortest in internodal length, which was also
characterized by maximum fruits per plant (9.12). BH 8 was the earliest
to flower (46.25 days) and harvest (88.00 days). BH 10 had the least

vulnerability index for mosaic (27.50). High phenotypic and genotypic
coefficients of variation were observed for seeds per fruit, average fruit
weight, yield per plant and fruits per plant.
High heritability coupled with high genetic advance was observed
for average fruit weight, yield per plant, fruits per plant, fruit girth and
fruit length.
Correlation studies and path coefficient analysis revealed that fruit
length and average fruit weight are the primary yield components as
evidenced from its high positive correlation as well as direct and indirect
effects on yield.
In the discriminant function analysis, the landrace BH 15
(Neyattinkara. Thiruvananthapuram) ranked first, followed by BH 23
(KAU local, KAU) and BH 5 (CO-I, TNAU). They were found to be
promising based on their superiority in yield, fruit quality, earliness in
male and female flowering, narrow sex ratio and mosaic resistance and
hence they may be utilized for further crop improvement.
Based on the analysis for genetic divergence, the 25 landraces of
B. hispida were grouped into seven clusters, with the highest intercluster
distance observed between clusters V and VII.
DNA isolated from the 25 landraces of B. hispida were subjected to
RAPD analysis. Out of the 40 decamer primers, twenty nine yielded
amplification products. A total of 83 RAPDs (average 2.08 bands per
primer) were generated by the 29 primers, of which 92.77 per cent were
polymorphic (77 bands) and six were monomorphic. Out of five primers
showing high level of polymorphism, three prormsing primers viz ..
OPA-O 1, OPA-07 and OPA-I3 were selected. The primer OPA-07 was
unique as it could distinguish maximum polymorphism among the
landraces tested while OPA-I3 produced maximum number of scorable
bands. The selected three primers yielded 20 scorable bands (average of

6.66 bands per primer) of which 2 were monomorphic and rest, 18 were
polymorphic (90.0 %).
The overall Jaccard's similarity coefficients ranged from 0.14 to
1.00. Cluster analysis revealed that at about 0.35 similarity coefficient,
the twenty five landraces of B. hispida grouped into two clusters.
Landraces with morphologically distinct smooth and waxy textured fruits
grouped into two major clusters. Considering the waxy textured group, it
formed a more divergent cluster than smooth textured group. With in the
group of waxy textured fruits, limited variation was detected among
landraces with small and medium sized fruits. Further, morphologically
similar landraces with large fruits form distinct clusters with in the major
clusters.
By characterizing all the twenty five landraces of Benincasa
hispida using morphological (selection index and D2 analysis) and
molecular (RAPD marker analysis) methods revealed that morphologically
distinct and superior lines were genetically differentiable. Also the RAPD
analysis gave a perfect differentiation of waxy textured group from smooth
textured group, which is in line with morphological characterization.