Hybridization between some Iranian and commercial apple cultivars and resistance assessment of the hybrids to Apple Powdery Mildew (Podosphaera leucotricha)

A crossing program was initiated between three native golab varieties (kohans, Soltani and Esfahan) and three commercial cultivars (Mcintosh, Red spur and Gala) and the relative susceptibility of genotypes to powsery mildew was assessed. At the time of swelling buds, commercial trees were isolated by cloth mesh. At the time of blossoming, several consecutive, hand pollination were carried out by pollen grains of male parents . After ripening, the fruit harvested and the seeds were planted in greenhouse condition. Apple powdery mildew spore suspension, prepared and three times in two days intervals sprayed on progenies at two to four leaf stage. Two weeks after the last spraying, assessment was carried out based on a 0-7 index. Of the 191, 2281, 9178 and 10949 seeds in 2008 to 2011, 69, 265, 438 and 180 progenies resistant obtained, respectively. Among the different crossing plans, Red spur♀ × Golabe Soltani♂, Red spur♀ × Golabe Kohanz♂, Gala♀ × Golabe Esfahan ♂and Gala♀ × Golabe soltani, had the highest rate of resistance level with the 177, 172, 164 and 157 progenies resistant, respectively based on the 4 years assessment. In the second assessment based on some horticultural traits 56 resistance genotypes selected and their resistance assessed in natural conditions for 3 years and grouped using a tree diagram after cluster analysis by SPSS software.