The genetic composition of hybrid Mangifera

Homoploid hybridization is known to play an important role in the evolution of plants, including many crop species, but can have different outcomes including introgression between parental taxa and the formation of new evolutionary lineages. We investigate the occurrence and consequences of hybridization between the economically important tree crop Mangifera indica (mango) and two congeneric species in Southeast Asia. A total of 90 samples of the hybrid M. odorata and its parental taxa, M. indica (mango) and M. foetida, along with 65 samples of a newly proposed hybrid, M. casturi and its putative parental taxa, M. indica and M. quadrifida, were sampled and genotyped using restriction site associated DNA sequencing. For each hybrid, we assessed population structure and admixture and indices of genetic diversity, including multilocus linkage disequilibrium. We found no evidence of introgression between M. foetida and M. indica cultivars from Southeast Asia, but find support for a hybrid origin of M. casturi. Both hybrids show low levels of intraspecific genetic diversity and individuals have high genetic identity and significant multilocus linkage disequilibrium. For both M. odorata and M. casturi, our results are consistent with hybrid lineages that have formed only a few times and have since been maintained clonally. While grafting may play a role in the continued propagation of these hybrids, we suggest that the ability of M. odorata and M. casturi to reproduce asexually through nucellar polyembryony has allowed the hybrids to persist independently of grafting.