INHERITANCE OF DOWNY MILDEW [Pseudoperonospora cubensis- (B & C) Rostow| RESISTANCE IN MUSKMELON (Cucumis melo L.)
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Date
2001-06-30
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MAHATMA PHULE KRISHI VIDYAPEETH, RAHURI-413 722, DIST. AHMEDNAGAR Maharashtra State (India)
Abstract
The present investigation entitled, "Inheritance of downy mildew [Pseudoperonospora cubensis (B & C) Ro stow) resistance in muskmelon (Cucumis melo L.)" was carried out with main objectives to identify the downy mildew resistant genotypes in muskmelon, to study the inheritance of downy mildew resistance and other horticultural characters and electrophoretic studies. The work was carried out at Instructional-cum-Research Farm and Tissue Culture Laboratory of Centre for Advanced Studies in Horticulture (Fruits), Department of Horticulture at Mahatma Phule Krishi Vidyapeeth, Rahuri during the year 1998-2001. Sixty-six genotypes in Kharif 1999 and selected genotypes in Kharif 2000 were screened for downy mildew resistance under natural epiphytotic conditions. Genotypes 55-1, 55-2 and 77 were identified as resistant to donwy mildew which recorded 13.63, 14.21 and 26.02 PDI (average of two screenings);respectively. PI 124111 F and PI 124112 were found to be susceptible to downy mildew which exhibited 53.89 and 52.28 PDI, respectively. Monoecious-3 (M3) susceptible to downy mildew was crossed with resistant genotypes 55-1, 55-2, 77, PI 124111 F and PI 124112 and the resultant five crosses were subjected for inheritance studies using six parameter (P1,, P2, F1,, F2, BC1, and BC2) model. For downy mildew resistance the presence of non-allelic interaction was evidenced. Estimates of six parameters indicated that almost all the types of interactions and gene effects were significant for expression of downy mildew resistance and duplicate type of epistasis were found to be significant in all the five crosses for this character. Complementary type of gene action was observed in 2 crosses for fruit number, 4 crosses in weight of fruit and 2 crosses for yield per plant and days to first harvest and total soluble solids. Neither complementary nor duplicate types of gene action were observed in M3 x 55-2 and M3 x PI 124112, respectively. Duplicate type epistasis were observed in all the 5 crosses for flesh : cavity (F:C) ratio, in 3 crosses for total soluble solids, 2 crosses for days to first harvest, 2 crosses for fruit number and 1 cross for weight of fruit and yield per plant, respectively. The electrophorogram of the soluble protein extracted from the seeds of indigenous and exotic genotypes of muskmelon revealed both qualitative (intensity of band) and quantitative (number of protein subunit bands) type of bands. A very intense band corresponding to M3 band No. 20 (Rm 0.75) is characteristics feature of susceptible lines, however, the same protein subunits appears to split into several low molecular weight subunits in resistant genotypes 55-1 and 55-2. The genotypes PI 124111 F and PI 124112 found to be susceptible were also very much similar to Monoecious-3 (M3). Total number of bands present were 31 and band No. 31 is common in all the genotypes. The presence or absence of some unique band discriminate some genotypes from the rest such as genotypes 55-1 by the presence of band number 17 and 20, PI 124111 F by the presence band 14 and PI 124112 by presence of bands 1 and 5. The similarity index was found maximum between genotype 113 and 114 and 55-2 and 113 (33.33) followed by Monoecious-3 and PI 124111 F (31.58). Further, based on presence or absence of bands, banding pattern, banding intensity and similarity index, it is concluded that downy mildew resistant genotypes 55-1, 55-2 and 77 are distinct from PI 124111 F and PI 124112. The latter two showed close affinity with downy mildew susceptible genotype Monoecious-3.
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