VARIABILITY STUDIES IN MELON (Cucumis melo L.) F2 POPULATION FOR RESISTANCE TO DOWNY MILDEW AND POWDERY MILDEW DISEASES AND MORPHOLOGICAL TRAITS
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Date
2017-06
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bengaluru).
Abstract
Melon (Cucumis melo L., 2n=24) of Cucurbitaceae family has great importance
because of its commercial value and is grown mostly for its fruits. Melon cultivation is
threatened by downy mildew and powdery mildew diseases which hinder the production
and reduce the quality of fruits. Indian melon landraces are being used worldwide as
disease resistant source in gene introgression to cultivated lines through different
breeding methods. In Karnataka state melon landraces are grown in small patches. In
our study, the F2 segregating populations developed using disease susceptible, superior
variety Kashi Madhu and downy mildew and powdery mildew resistant landrace of
Karnataka, COHB38 were field evaluated at College of Horticulture, Bengaluru for
resistance to diseases and morphological traits based on DUS guidelines. Downy
mildew disease resistance screening included parents, F1 and two F2 populations (191
and 102 F2s) of Kashi Madhu x COHB38 under natural disease conditions. Another set
of F2s (152) along with parents and F1 were evaluated for powdery mildew disease
resistance. The reaction of F2s for both the diseases showed a continuous distribution
from highly resistant to highly susceptible phenotypes and revealed the quantitative
nature of resistance in resistant parent COHB38. Very wide variation was observed
among F2s for all morphological traits. Among 31 qualitative characters, 13 were
dimorphic and 18 were polymorphic. Out of 15 quantitative characters, 14 were
polymorphic except seed length. The resistant plants along with superior fruit characters
can be selfed further and utilised in developing superior melon lines resistant to
diseases.