Results of some apple hybrid populations to the attack of scab and powdery mildew under natural conditions

Apple scab, caused by the fungus Venturia inaequalis, and powdery mildew, caused by the fungus Podosphaera leucotricha, are two of the most significant diseases affecting apple production worldwide. These diseases can lead to substantial crop losses and often require frequent fungicide applications, with negative environmental impacts and the development of fungicide resistance. Apple breeding programs frequently aim to develop cultivars exhibiting resistance to scab and powdery mildew. This is also the case of a breeding program initiated at FRDS Bistrita to obtain hybrids resistant/tolerant to scab and powdery mildew, accompanied by superior fruit qualities and a later harvest period. Thus, the pollinations were performed on apple trees in 2023. The experiment was organized into two hybridization schemes involving six apple cultivars. Scheme 1 consisted of five maternal genitors ('Auriu de Bistrița', 'Jonathan', 'Idared', 'William’s Pride', and 'Bistrițean') and one paternal genitor ('Generos'). Scheme 2 consisted of one maternal genitor ('Generos') and five paternal genitors ('Auriu de Bistrița', 'Jonathan', 'Idared', 'William’s Pride', and 'Bistrițean'). The aim of this study was to evaluate the hybrids of these crosses in terms of early response to natural infection with apple scab and powdery mildew. Results showed no symptoms of scab infection on the leaves of the hybrids, while 83.8% of the total showed no symptoms of powdery mildew infection. The hybrid combination with the lowest percentage of infected hybrids was 'William’s Pride x Generos' (10.4%), closely followed by the 'Auriu de Bistrița x Generos' hybrid combination (12.5%). The highest percentage of infected hybrids was observed in the 'Jonathan x Generos' hybrid combination (20.0%).