Impact analysis of clonal rootstocks × scions interface on scab and Alternaria leaf blotch of apple

The focus of the present research was to find out the influence of clonal rootstock × scion combinations on two major fungal foliar diseases of apple viz., scab and Alternaria leaf blotch under temperate conditions of India. The experimental trial was laid during 2015–2017 cropping season under well established high density orchard system having two cultivars viz., Silver Spur and Vance Delicious grafted on four clonal rootstocks viz., M4, M7, MM106 and M9. During the present study, the best rootstock × cultivar combination with respect to leaf scab proved to be MM106 × Vance Delicious which recorded 26.33 per cent incidence and 12.00 per cent severity. However, the lowest fruit scab incidence and severity of 15.33 and 4.13 per cent and Alternaria leaf blotch incidence and severity of 21.00 and 07.25 per cent, respectively was observed in M7 × Vance delicious. The interface effect of M7 × Vance Delicious against. The overall response of rootstocks, clearly indicates the impact of rootstock MM106 on tested cultivars in which lowest leaf scab incidence and severity (28.50 and 13.76%) was recorded followed by M7 (50.16 and 26.73%), M4 (49.33 and 28.53%) and in seedling rootstock (77.00 and 43.10%). In case of fruit scab, the impact of M7 rootstock on tested scions recorded lowest fruit scab incidence of 22.66 per cent with severity of 08.73 per cent followed by M4 (51.00 and 22.60%), MM106 (58.33 and 22.26%) and seedling rootstock (78.33 and 38.40%). The response of rootstocks on the selected scions against Alternaria leaf blotch incidence and severity was observed lowest in rootstock M9 (25.17 and 09.10%) followed by M7 (32.66 and 10.09), seedling (46.16 and 15.76%), MM106 (46.66 and 15.33%) and in M4 (46.66 and 16.86%).