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Sudan Journal of Agricultural Research

Breeding for resistance to powdery mildew Sphaerotheca fuliginea (Schlecht ex Fr. PolL) in squash (Cucurbita pepo L.)
 

E.A. Ahmed^l, A. E. Eljack ² and Y.F.Mohamed².


Abstract:

Powdery mildew Sphaerotheca fuliginea (Schlecht ex Fr. Poll.) is an important disease of squash, causing severe damage. The popular cultivar in the Sudan "Eskandarany" is highly susceptible. Four breeding lines, obtained from Cornell University, USA breeding program, were evaluated for powdery mildew resistace (PMR). Evaluation was conducted under natural conditions of infection in season 1993/94 in the Gezira University farm at Abu Haraz. A disease severity scale of 1 to 9 was used, where 1 at one end representing high susceptibility and 9 at the other end representing strong resistance (immunity). Tow parents, "94-38-1" and "94-36-1", were selected as having PMR=8. The two parents were crossed with Eskandarany. The F) progenies showed dominant resistance (PMR=7). In the F₂ progenies, about 10% of the plants had PMR=7, similar to the resistant check (Astia, F₁ hybrid). In the F₃ progenies, fast fixation of resistance was observed, where 80-90% of the plants had PMR ≥7. Astia, the resistant check, did not show a uniform level of resist ance. This variability in resistance is suggested to be due to fruit load. Leaving fruits on plants for seed production had led to a pronounced decrease in the level of resistance towards plant maturity. The specific causal agent of powdery mildew in the Sudan was identified as Sphaerotheca fuliginea race 2, and that was done through laboratory examination and the use of eight differential hosts of known reactions.

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Sudan Journal of Agricultural Research Vol. 1(1998) PP. 57-60