DIFFERENTIATION OF PARASITISM IN POWDERY MILDEW FUNGUS, SPHAEROTHECA APHANIS VAR. APHANIS BRAUN, TO STRAWBERRY CULTIVARS
Y NAKAZAWA1, K UCHIDA1, J INOUE2, T TAKEDA1, T AMANO1 and N KITA2
1ZENNOH Agricultural R&D Centre, 5-5-1 Higashiyahata, Hiratsuka, Kanagawa 254, Japan; 2Kanagawa Institute of Agricultural Science, Kamikisawa, Hiratsuka, Kanagawa 254, Japan
Background and objectives
In the present study, we collected monoconidial isolates of the fungus and investigated difference in their pathogenicity to the selected strawberry cultivars. We also conducted genetic studies on the resistance of several strawberry cultivars to the fungus.
Materials and methods
For the pathogenicity test, freshly formed conidia of each isolate were scattered onto the lower surface of the leaf disks from nine strawberry cultivars, Toyonoka, Nyohoh, Reikoh, Himiko, Hokowase, Doner, Kogyoku, Harunoka and Fukuba. The degree of mildew infection was evaluated 7 days after inoculation.
Results and conclusions
Against race 0, progenies obtained from the cross between 'Toyonoka' and 'Nyohoh' segregated into 1:1 and S1 of 'Toyonoka' into 3:1 for resistant:susceptible, respectively, whereas S1 of "Nyohoh" were all susceptible. All the progenies were susceptible to race 1. These results clearly indicate the existence of physiological races in Japanese population of S. aphanis var. aphanis on strawberry, which correspond to a major gene for resistance in host cultivars.