K K Pramanick
Indian Agricultural Research Institute, India
"Apple, the premier table fruit of the world, has been under cultivation since time immemorial. The selection of suitable rootstock of apples for a certain tract has been an important investigation.All successful apple rootstocks, either seedling or clonal, are of the genus Malus. In early days, French crab seedlings (Malus sylvestris) were widely used in the USA as rootstocks. Some of the Asiatic species of apples are apomictic and bred true from seeds even when pollinated by other species. These apomictic species have been used as rootstocks for commercial apple cultivars with the hope that they might be of value in controlling tree growth and age of fruiting. Thus, the crab apples can play a pivotal role for the improvement of apple through proper utilization of their potentiality. A number of crab apples have been found growing wild in the Himalayas. Botanically only two species of Malus have been identified viz. Malus baccata and Malus sikkimensis. However, this botanical classification does not clearly reflect the existing genetic variability. At the IARI Regional Station for Horticulture at Shimla, India seven types of Malus baccata and two types of Malus sikkimensis from different agro-climatic regions have been collected. Significant differences for their botanical and horticultural traits have been observed. The crab apples from Shillong and Srinagar exhibited a very good propagation potential, showed a high degree of resistance to powdery mildew and apple scab, while that from Shillong produces semi vigorous trees and Srinagar produces very vigorous trees when used as rootstock. All the crab apples exhibited a considerably less chilling hour requirement as compared to the standard apple rootstocks M 9 and MM106. Thus, these crab apples are likely to improve the productivity of apple varieties in areas where the chilling requirement is not being fully met. The germplasm that holds promise for using rootstock viz., Malus baccata (Shillong), Malus baccata (Srinagar) etc. or in breeding programme for disease resistance or as pollinizers has been identified for the improvement of apple. An ideal rootstock should posses uniformity in vigour, resistance to diseases and pests without impairing the productivity and quality."