Morphological and biochemical diversity among the Malus species including indigenous Himalayan wild apples

Abstract

In the present investigation, 32 Malus species including 12 indigenous Himalayan wild apples were evaluated during 2014–2015, for their morphological (14 No.) and biochemical (14 No.) variabilities based on 28 parameters. The leaf related attributes like leaf shape, leaf apex shape, leaf base shape, leaf blade margin and tree attributes like tree habit, suckering tendency, burrknot tendency and presence of lenticels on shoot exhibited considerable variation. The maximum coefficient of variation value was recorded for foliar peroxidase activity (98.18%) followed by catechin (91.32%) content. Principal component analysis (PCA) revealed that the first five principal components (PC1, PC2, PC3, PC4 and PC5) together accounted for more than 50% variation of the total observed variations. The PC1 strongly integrated with the traits like tree habit, leaf blade length, leaf blade width, rutin, phloridzin, chlorophyll a, chlorophyll b, − chlorophyll a:b, total chlorophyll and total phenolics content, which were found to be effective parameters for explaining the natural variability among the studied Malus species. The dendrogram generated based on unweighted Neighbhor-joining method clustered all the Malus species including the indigenous wild apples into three distinct clusters. Scatter plot based on PC1 and PC2 suggested high morphological and biochemical diversity among the Malus species including the indigenous wild apples. The cluster analysis and scatter plot revealed that the indigenous wild apples were quite diverse as observed for the exotic Malus species; though there were no separate groups detected. The higher diversity for endogenous biochemical compounds indicates differential physiological behaviour of Malus species under the prevailing environmental conditions. These findings revealed that there were several biochemical constituents, which could serve as effective indices for indirect selection of potential biotic and abiotic stresses resistance/tolerance Malus species for their potential use in genetic improvement programmes. Similarly, knowledge on graft compatibility with respect to wild Malus could help in exploiting them as new rootstock genotypes. These parameters are known to influence the expression of different traits in scion genotypes upon grafting and thus could help in sustaining the apple production in Indian Himalayan region under changing climate situations The potential genotypes based on their morphological and biochemical parameters identified like M. baccata (Khrot), M. baccata (Kinnaur), M. baccata (Pangi), M. baccata (Rohru), M. baccata (Shillong), M. hilleiri, M. micromalus, M. prunifolia (Maruba), M. prunifolia (Ringo-Assami), M. sieversii and M. spectabilis suggested them to be quite diverse. Besides, some indigenous Himalayan crab apples were also identified, which have inherent potential to serve as valuable genetic resources for rootstock improvement programmes.