Genetic diversity in mandarin landraces and wild mandarins from China based on nuclear and chloroplast simple sequence repeat markers

Abstract

SummaryLandraces and wild germplasm are important citrus genetic resources. Knowledge of the genetic diversity of this germplasm provides an opportunity both to mandarin breeding programmes and to germplasm conservation strategies. Genetic diversity of 33 loose-skin mandarin landraces and 19 wild mandarin accessions were analysed with ten nuclear simple sequence repeat (nSSR) and eight chloroplast simple sequence repeat (cpSSR) markers. Our analysis of nuclear and chloroplast genome polymorphism showed that the genetic diversity in wild populations was slightly higher than that found in landraces, with polymorphic information content values of 0.6138 and 0.5091 at nSSR loci, and 0.4921 and 0.3769 at cpSSR loci, respectively. Overall, 60 nSSR alleles and 19 cpSSR haplotypes were identified, and all but seven accessions were unambiguously discriminated by nSSR markers. Five groups of landraces and two groups of wild mandarins were identified based on the nSSR data, and two groups each of landraces and wild mandarins were identified at the cpSSR loci. Different distribution patterns of landraces and wild mandarins were observed between dendrograms constructed using these two marker systems, and hybrid origins for several landraces were suggested by these results. Combined analysis also suggested that, among wild mandarin, ‘Chongyi’ showed the closest relationship to landraces, and that landrace ‘Chazhigan’ was the primary genotype among landraces.