PHYSIOLOGICAL AND MOLECULAR CHARACTERISATION OF GYNOECIOUS LINE AND GENETICS OF FRUIT TRAITS IN BITTER GOURD (Momordica charantia L.)
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Date
2015
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DIVISION OF VEGETABLE SCIENCE INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Bitter gourd is a monoecious plant, which is mainly cultivated in tropical and
subtropical Asia. Phytohormones have implications on various aspects of
reproductive organ development in unisexual as well as bisexual plants. In dicots,
higher levels of ethylene and auxins are positively correlated with female sex
expression, whereas gibberellin favours differentiation of male sex organs.
Therefore, in the present investigation, we characterized monoecious and gynoecious
line at early stage by estimation of ethylene and GA3. However, expression of Mc
ACS2 gene which is solely responsible for ethylene action was studied at four
different stages of conversion of female to hermaphrodite buds by spray of silver
thiosulfate @6mM. This was further validated by quantification of ethylene, GA3 and
enzymatic activity of Guaiacol peroxidase and total antioxidants capacity at all four
stages. Reduction in expression of Mc-ACS2 gene was observed after three days of
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st spray and increased during the formation of hermaphrodite buds but its expression
was less in modified (hermaphrodite) buds than the female buds. Ethylene was also
found to be less in hermaphrodite buds than female buds whereas, GA3 was found to
be more in silver thiosulfate treated buds than female buds. Activity of both enzymes
were higher in treated buds with respect to untreated ones. Hence, silver ion action
hypothesis can be proposed as: it reduces ethylene perception resulting in less
accumulation of McACS2 gene mRNA and endogenous GA3 cooperation leads to
formation of hermaphrodite flowers. Predominately gynoecious line was extracted
from advanced backcross progenies, viz., BC2F4, BC2F5 and BC2F6 of Pusa Do
Mausami and DBGy 201. Sex ratio was highly heritable in all three generations with
maximum in BC2F6 (86.83%) generation, suggesting the possibilities of high genetic
progress through selection. However, fruit number, yield and harvest index had
maximum heritability in BC2F5 generation. Sex ratio is negatively correlated with
yield whereas number of fruits and harvest index had significant positive relationship
with yield. Therefore, these traits in combination can be good criteria for selection in
advanced generations for bitter gourd. One line was also extracted from BC2F6
generation as predominately gynoecious line.
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Inheritance pattern of fruit length, tubercles, curviness and gene action of
economic traits was studied through generation mean analysis by using Sel-2 and
Pusa Purvi. The inheritance of tubercles and curviness of fruits in bitter gourd,
governed by a single pair of nuclear gene and prominent tubercles was dominant
over non-tubercles whereas, straight fruit was dominant over curved fruit. Fruit
length was reported to be quantitatively inherited and more than 4 genes involved in
controlling this trait. Duplicate epistasis for all the studied traits indicated the
possibilities of obtaining transgressive segregants in later generations. Presence of
additive, dominance gene effects and epistatic interactions for all the characters
studied in cross Sel-2 × Pusa Purvi indicating the importance of both additive and
non-additive gene actions in the expression of the characters. Morphological
characterisation was carried out for both parents (Sel-2 and Pusa Purvi) and their
direct and reciprocal hybrids. Significant variation was reported for plant
morphology, flowering traits and seed characters. The hybrids were either likewise
their respective female parent for most of the traits or intermediate for few qualitative
traits. The most important loading traits obtained by Principal Component Analysis
(PCA) were female flower pedicel length, bract width, bract length, style length,
ovary length, male flower bract length, fruit length and weight of seed and its
diameter. Therefore, both of these parents have potential to be used as breeding
material for development of desirable segregants
Description
T-9204
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