Phylogenetic relationship among potential citrus rootstock species based on seeds characteristics and germination metrics

Abstract

Wild citrus species could be potentially used as rootstocks in the citriculture industry. Seed, germination, and seedling characteristics and their metrics are important traits associated with rootstocks and their evolutionary relationship. However, the information available is very dispersed, thus affecting propagation and field production of citrus. Fifteen potential citrus rootstocks, viz., Citrus aurantifolia, C. maxima, C. jambhiri, C. karna, C. latipes, C. limonia, C. limon, C. macroptera, C. medica, C. paradisi, C. reshni, C. trifoliata, C. taiwanica, C. volkameriana, and C. indica, were studied to understand their germination and growth behaviours and their phylogenetic relationship. Results showed that the maximum seed characteristics, germination, seedling growth and their metrics were obtained in C. jambhiri, C. latipes, C. limonia, C. maxima, and C. volkameriana. While the chlorophyll index was recorded as the maximum in C. limon (80.8±3.7) and C. medica. Germination was strongly correlated with germination speed index (.746**), mean daily germination (.845**), peak value (0.512**), and germination value (0.596**). Principal component analysis revealed the presence of a wider variability for germination and seedling growth traits, with the first five components (eigenvalue > 1) contributing 78.69% of the total variation. Phylogenetic analysis revealed that cluster I was monogenotypic (C. trifoliata) and cluster II comprised commonly used rootstocks, indicating their close relationship. It is concluded that C. jhambhiri, C. limonia, C. maxima, and C. latipes had higher germination, growth and vigour. Germination percent and germination metrics could be an important selection criteria for the improvement and utilization of this species in propagation.