Identification and characterization of Apple (Malus × domestica Borkh.) bud sports mutations in the apple growing Northwestern Himalayan region

Abstract

Spontaneous mutations are exceedingly rare, and bud-sport selection is a promising horticultural breeding strategy that adds value to natural selection by enabling plants to adapt better to climate variability. Based on these observations, the research had been carried out in various apple-growing orchards in the Northwestern Himalayan area, particularly the districts of Kinnaur, Lahaul, and Spiti in the state of Himachal Pradesh. The research led to the identification of 12 bud sports originating from cv. Royal Delicious, 9 of which were found in Kinnaur and 3 in Lahaul and Spiti, which differed in fruit color and belonged to distinct groups. Eight of the twelve bud sports were early, solid-colored, and early maturing, whereas the remaining four were late-colored, late-maturing bud sports. The identified bud sports mature at different rates, and harvesting times varied from the first week of September to the fourth week of October. According to biochemical analysis, 'KAH-1′ and 'DDK' had the highest TTS (16.10 °Brix), total sugars (11.90 %), and titratable acidity (0.70 %). Based on the molecular analysis, one EST (E2) and five genomic SSR primers (HI04E04, HI01D06Y, BACSSR58, GD100, and CH01H01) were found to be informative and resulted in significant polymorphism between seven different bud sports and their mother plants. Bud wood from every identified apple bud sport was collected and conserved to produce plants for future investigation. Commercialization of such bud sports will not only raise market values but also lead to a reduction in the use of coloring chemicals for fetching early market, whilst late coloring and late-maturing bud sports will help to extend the season of apple fruit availability. These detected bud sports could represent a valuable gene pool that could be exploited as a source of genetic material in apple breeding programs or introduced as a new cultivar after systematic evaluation and validation through multi-location field trials.