Reaction of Muskmelon Genotypes to Races 1 and 2 of Sphaerotheca fuliginea in Israel.

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Cucurbit Genetics Cooperative Report 11:47-49 (article 20) 1988

Yigal Cohen and Helena Eyal
Department of Life Sciences, Bar-Ilan University, Ramat-Gan Israel 52100

Races 1 and 2 of Sphaerotheca fuliginea (Schlecht. ex. Fr.) Poll. cause powdery mildew on cucurbits in Israel (5). Race 3 was not reported in the country. Race 1 predominates in the winter in greenhouse-grown cucumbers and muskmelons, whereas both races 1 and 2 are found in the summer in the open field. (Y. Cohen, unpublished). Race 2 was considered less aggressive on muskmelon than race 1 in Israel. (Karchi, in (3) with no experimental evidence.) Our preliminary observations with mixed (1:1 ratio) race inoculations in greenhouse-grown muskmelon revealed predominance of race 2 one month after inoculation.

In this paper we report on the pathogenicity of races 1 and 2 to cultivars, breeding lines and F1 hybrids of Cucumis melo L. Plants were grown in 0.5L pots in the greenhouse. When developed two fully expanded true leaves they were inoculated with either race in walk-in growth chambers (23 C, 12h photoperiod). Race 1 was maintained on ‘Ananas-Yokneam’ whereas race 2 was maintained on ‘PMR-45′ plants. Disease records were taken 14 days after inoculation. Each inoculation test was done three times. Results summarized in Table 1 show that 23 our of the 43 genotypes tested were resistant to race 1 and 11 genotypes were resistant to both races 1 and 2. No genotype was resistant to race 2 and susceptible to race 1. Most genotypes resistant to both races are breeding lines or plant introduction entrees, indicating the difficulty in incorporating race 2 resistance into commercial cultivars. Indeed, race 1 resistance genes are dominant and available in “PMR 45’ (Pm-1, PI 124111 (Pm-3) and PI 124112 (Pm04), whereas race 2 resistance genes available in PI 124111 (1) and PI124112 are partially dominant. (Y. Cohen, H. Eyal, and D. Deningsbach, unpublished). The dominant gene B in PI 414723 against race 2 was effective in Monfavet, France 1983 but not in 1984 (3).

Table 1. Pathogenicity of Sphaerotheca fuliginea race 1 and race 2 to genotypes of Cucumis melo var. reticulatus

Severity of powdery mildew

Genotype
Race 1
Race 2
Remarks
1. Ananas-Yokneam +++ +++
2. Hemed ++ ++
3. Ein-Dor – +*
4. Sharon F1 +* +* *severe in stems
5. Galia F 1 + +++ *severe in stems
6. Makdimon F1 +* +HS
7. Golden Perfection +++ +++ *in stems only
8. Hale’s Best 36 +++ ++
9. Hale’s Best Jumbo +* ++ *severe in stems
10. Top Mark +++ +++
11. PMR 45 – ++
12. Perlita 45 – nt
13. Smith’s Perfect +++ +++
14. Cum Laude ++ +++
15. Delicious 51 +++ +++
16. Honey Dew Green Flesh +++ +++
17. Planter’s Jumbo +++ ++* *on stem mainly
18. Gulfcoast – nt
19. Green Ice ++ nt
20. Hiline – nt
21. Gulf Stream – +
22. Amarello +++ +++
23. Sierra Gold + Sg. +++
24. Edisto 47 – +
25. Rio Gold – –
26. Tam Uvalde – +
27. GA 47 – +
28. Cinco -* +*HS *moderate on stems
29. Chilton – + *moderate on stems
30. Mission F1 – +
31. Seminole – +
32. Charity Ball – +HS
33. Emerald Pearl +++ –
34. Doublon – +++
35. Charantais – T – nt
36. PMR 5 – –
37. PMR 6 – –
38. MR – 1 – –
39. PI 124111 – –
40. PI 124111F – –
41. PI 124112 – –
42. Male-Sterile1 – –
43. Dulce – –

Scale:

  • – no apparent disease development
  • + one or two colonies per leaf with sparse sporulation
  • + up to 5 colonies per leaf with abundant sporulation
  • ++ up to 10 colonies per leaf with abundant sporulation
  • +++ 20 or more colonies per leaf with abundant sporulation
  • HS – hypersensitive response
  • Sg – segregates
Sources: genotypes No.:
Hazera, Israel 1, 2, 3, 4, 5, 6
Petoseed 11, 12
Asgrow 20, 22, 30,
Hollar 8, 9, 13, 17, 18, 23, 26, 29
USDA 7, 10, 14, 15, 16, 19, 22, 25, 27, 28, 31, 36, 37, 38, 39, 41, 42, 43
Sakata, Japan 32, 33
INRA, France 34, 35

Literature Cited

  1. Cohen, Y, and S. Cohen. 1986. Genetics and nature of resistance to race 2 of Sphaerotheca fuliginea in cucumis melo PI 12411. Phytopathology. 76:1165-1167.
  2. Harwood, R.R. and D. Markarian. 1968. A genetic survey of resistance to powdery mildew in muskmelon. J. Heredity 59:213-217.
  3. McCreight, J.D., M. Pitrat, C.E. Thomas, A.N. Kishaba, and G.W. Bohn. 1987. Powdery mildew resistance genes in muskmelon. J. Amer. Soc. Hort. Sci. 112:156-160.
  4. Pitrat, M. 1986. Gene list for muskmelon (Cucumis melo L.) Cuc. Gen. Coop. Rept. 9:111-120.
  5. Rudich, J., F. Karchi, and N. Eshed. 1969. Evidence for two races of the pathogen causing powdery mildew of muskmelon in Israel. Isr. J. Agric. Res. 19:41-46.
  6. Sitterly, R.W. 1978. Powdery mildew of cucurbits, pp/ 359-379 in: The Powdery Mildews. Spencer, M.D., ed. Academic Press. London. 565 pp.