Application of Hybridization Breeding Technique for Fire Blight Resistance on Cydonia Oblonga: A Base Study on Susceptibility, Heterosis, and Heterobeltiosis Parameters

Erwinia amylovora: Burrill. is the most important disease affecting quince cultivation and breeding of resistant varieties is seen as the key solution. As a result of hybridizations, 223 hybrids were obtained from 9 different combinations and susceptibility indexes (SI) of these hybrids were determined by artificial inoculations. Among the tested seven parental cultivars, Ege 25, Altın 35, Zeybek 35, and Ayva B-35 were found fire blight resistant while others were detected as moderately susceptible. SI of hybrids were changed between 14.77 and 52.94% regardless of hybrid combinations and 77.60% of obtained hybrids took place in resistant (10.1–30%) group. Reciprocal combinations showed that using resistant cultivar as a male parent was more effective than using maternal parent for transferring resistance. Heterosis (Ht) rates between combinations were found significant (p < .0004), while heterobeltiosis (Hbt) were not (p < .0623). Ht and Hbt ranged between −2.82–13.54 and −4.20–6.72 in populations, respectively. The maximum and significant heterotic effect was observed in Quince A × Ayva B-35 and its’ reciprocal combination. In moderately susceptible × resistance combination, 83.33% of F₁ were determined to be resistant. On the other hand, hybrids from resistance × resistance combination were distributed in three groups as resistant, moderately susceptible and susceptible. According to these results, it could be said that (1) fire blight resistance genes in quince are recessive, (2) use of resistant varieties as pollinators is more successful in transferring resistance to hybrids, (3) open pollination treatment is an essential and easy way in terms of obtaining resistant hybrids if the orchard has resistant pollinator, and (4) heterobeltiosis for fire blight resistance is important.