Downy Mildew (Pseudoperonospora cubensis B & C) Resistance in Melon (Cucumis melo L.)

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Cucurbit Genetics Cooperative Report 16:40-41 (article 14) 1993

R.G. Somkuwar and T. A. More
Division of Vegetable Crops, Indian Agricultural Research Institute, New Delhi – 110012, INDIA

Downy mildew has become a major threat to commercial cucurbits including melon and cucumber in India (5). In the sub-tropical pats during the premonsoon rains and in other humid and high rainfall areas, it is a devistating disease. In several trials conducted during rainy season by Dr. T. A. More at Delhi he noted almost 100 percent losses in cucumber and melon (4). He also observed that ‘Phoot’ or snapmelon (Cucumis melo var. momordica)., a non-dessert type of Indian origin and FM 1 of U.S. origin hold resistance to downy mildew. Hence, efforts were made to screen advanced progenies (F6 and F7) of ‘Phoot’ (R) x Monoecious-4 (S) and FM 1 (R) Pusa Madhuras (S) crosses for resistance to downy mildew thrice under the natural epiphytotic conditions (Table 1) as per the procedure of Bonnet and Blancard (1) and also to study their performance in two replicated yield trials.

Results indicated that lines VRM 1-3, 5-10, 7-12, and 16-5 # B-1 of FM 1 x Pusa Modhuras cross and only one line VRM 31-1-2- of ‘Phoot’ x Monoecious-4 cross were highly resistant to downy mildew (Table 1). Combining these results with two replicated yield trials, two lines namely VRM 5-10 and 31-1-2 showed promise for downy mildew resistance and high productivity. These lines have attained homozygosity for major horticulturally important characters and now are in F9 generation.

Detailed study on inheritance of downy mildew resistance under artificial inoculation conditions in three resistant x susceptible crosses using six generations – P1, P2, F1, F2, BC 1 and BC 2 (2, 3) was conducted. Iheritance of downy mildew resistance is governed by two dominant genes in ‘Phoot’ x Monoecious-3 and ‘Phoot’ x Pusa Madhuras crosses and two recessive genes are responsible for the same in ‘Phoot’ x Lucknow Safeda cross. Duplicate type of epistaasis was evidenced in all the crosses.

F6

F7

Breeding lines

Rainy season – 1990

Summer season – 1991

Rainy season – 1991

Average
VRM-1-3 NT 12.5 20.8 16.7
VRM-5-10 8.3 31.3 42.9 27.5
VRM-7-12 12.5 33.9 21.9 22.8
VRM-16-5 # B-1 5.6 17.5 NT 11.6
VRM-31-1-2 7.1 22.3 21.9 17.8
Phoot (R)-Check 3.1 9.4 17.9 10.1
Monoecious-4(S)-Check 71 62.5 NT 67.1
Total no. of lines tested 33 18 10 —

R = Resistant, S = Susceptible, NT = Not tested
*All these lines are in F9 generation at the present

Literature Cited

  1. Bonnet, A. and D. Blancard. 1987. Resistance of radish (Raphanus sativus L. to downy mildew Peronospora parasitica. Cruciferae Newsletter 12:98-99.
  2. Hayman, B.I. 1958. The separation of epistatic from additive and dominance variation in generation means. II. Genetica 31:133-146.
  3. Hayman, B.I. 1960. The separation of epistatic from additive and dominance variation in generation means. II. Genetica 31:133-146.
  4. More, T.A. 1989. Phoot (Cucumis melo var. momordica) resistant to downy mildew. Personal communication.
  5. Palti, J. 1974. The significance of pronounced divergence in the distribution of Pseudoperonospora cubensis on its crop hosts. Phytoparasitica 2:109-115.
  6. Sambandam, C. N., V.A. P{arthasarthy, and S. Anthony Raj. 1979. Reastion of certain forms of Cucumis to downy mildew. AUARA 7/8:149-150.