Morphological diversity within litchi (Litchi chinensis Sonn.) based on leaf and branch traits

Abstract

Eighteen morphological traits of leaf and branch were employed to discriminate 146 Chinese litchi germplasm, as well as to assess their morphological diversity. Results showed that litchi accessions were highly diversified in characteristics of leaf and branch. Six quantitative traits exhibited high degrees of variability with significant differences between accessions. Principal component analysis (PCA) revealed that the first two components were responsible for 36.43% of the phenotypic variability. Traits of leaflet length, leaflet interval, ratio of leaflet length to width, petiole length, leaflet apex shape, pairs of leaflets, leaflet margin and leaflet width integrated by PC1 and PC2 were the most effective parameters to discriminate accessions. Based on UPGMA cluster analysis, accessions were divided into two main groups which corresponded to different fruit maturation time. The first main cluster mainly contained extremely early-, early- and mid-maturing accessions, while the second main cluster were mainly composed of late- and extremely late-maturing accessions. Furthermore, significant differences existed in characteristics of leaf and branch between accessions with extremely early, early or mid-maturity and accessions with late or extremely late maturity. Finally, the wild litchi accessions were clustered together with some late-maturing litchi cultivars, indicating that the leaf and branch traits of late-maturing cultivar might subject to relaxed selection pressures during the evolution.