Genetics of resistance in <Emphasis Type="Italic">Luffa cylindrica</Emphasis> Roem. against <Emphasis Type="Italic">Tomato leaf curl New Delhi virus</Emphasis> |
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Authors: | Sabina Islam A D Munshi Bikash Mandal Ravinder Kumar T K Behera |
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Institution: | (1) Division of Vegetable Science, Indian Agricultural Research Institute, New Delhi, 110012, India;(2) Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi, 110012, India |
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Abstract: | Sponge gourd is a popular vegetable grown throughout India. Tomato leaf curl New Delhi virus, the causal virus of tomato leaf curl disease, has recently been reported to be associated with sponge gourd, causing up
to 100% crop loss under epidemic conditions. We have collected 30 genotypically diverse genotypes of sponge gourd from different
parts of India, screened these for resistance under natural epiphytotic conditions, and then confirmed the results through
challenge inoculation with a purified strain of the virus under insect-proof greenhouse conditions. The minimum vulnerability
index was recorded in genotype DSG-6 (3.33), followed by DSG 7 (6.0) under the challenge (whitefly-populated) inoculation
conditions. Two susceptible genotypes (‘Pusa Sneha’ and NSG-1-11), both possessing desirable fruit characters, were crossed
with the two most promising resistant lines (DSG-6 and DSG-7) and the disease reaction of segregating and backcross generations
studied through challenge inoculation with a purified strain of virus under insect-proof greenhouse conditions. A chi-square
(χ2) test of frequency distribution based on the vulnerability index of the F2 progenies of the two resistant × susceptible crosses revealed monogenic dominant Mendelian ratio 3(R):1(S) to be the best
fit in all crosses. This monogenic dominant model was further confirmed by the 1(R):1(S) ratio found to be best fit for the
test cross with the susceptible parent. These results reveal that resistance to Tomato leaf curl New Delhi virus associated with yellow mosaic disease of sponge gourd is controlled by a single dominant gene in the genetic background of
the resistant parents (DSG-6 and DSG-7) and that these two lines can be effectively utilized for the development of high-yielding
and yellow mosaic disease-resistant varieties/hybrids of sponge gourd. This is the first conclusive identification of a resistant
source and the inheritance of resistance against Tomato leaf curl New Delhi virus in sponge gourd. |
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