Abstract
Crop wild relatives (CWR) are an indispensable source of alleles to improve desired traits in related crops. While knowledge on the genetic diversity of CWR can facilitate breeding and conservation strategies, it has poorly been assessed. Cultivated bananas are a major part of the diet and income of hundreds of millions of people and can be considered as one of the most important fruits worldwide. Here, we assessed the genetic diversity and structure of Musa balbisiana, an important CWR of plantains, dessert and cooking bananas. Musa balbisiana has its origin in subtropical and tropical broadleaf forests of northern Indo-Burma. This includes a large part of northern Vietnam where until now, no populations have been sampled. We screened the genetic variation and structure present within and between 17 Vietnamese populations and six from China using 18 polymorphic SSR markers. Relatively high variation was found in populations from China and central Vietnam. Populations from northern Vietnam showed varying levels of genetic variation, with low variation in populations near the Red River. Low genetic variation was found in populations of southern Vietnam. Analyses of population structure revealed that populations of northern Vietnam formed a distinct genetic cluster from populations sampled in China. Together with populations of central Vietnam, populations from northern Vietnam could be subdivided into five clusters, likely caused by mountain ranges and connected river systems. We propose that populations sampled in central Vietnam and on the western side of the Hoang Lien Son mountain range in northern Vietnam belong to the native distribution area and should be prioritised for conservation. Southern range edge populations in central Vietnam had especially high genetic diversity, with a high number of unique alleles and might be connected with core populations in northern Laos and southwest China. Southern Vietnamese populations are considered imported and not native.
Highlights
Crop wild relatives (CWR) are wild species closely related to cultivated plants, including all direct progenitors of crops
We assessed for the first time the genetic variation of Vietnamese populations of Musa balbisiana and complemented them with populations sampled in the Yunnan and Guangdong province of compared to more feral populations in Hainan (China), as well as a population of Hainan island
In relation to studies that assess the genetic variation of populations of other CWR species using Simple Sequence Repeat (SSR) (e.g. [80,81,82]), the genetic variation we found in all M. balbisiana populations was rather low, with observed heterozygosity levels ranging from 0.05 to 0.28 with an average of 0.19
Summary
Crop wild relatives (CWR) are wild species closely related to cultivated plants, including all direct progenitors of crops. Because of their relatedness, CWR provide useful trait characteristics for crop improvement such as stress tolerance and yield increase [1]. CWR are believed to become even more important for breeding in the near future due to climate change and increasing food demand [2,3]. Conservation of CWR in gene banks improves the accessibility of CWR to breeders. Highly advanced genomic methods allow faster access to these genetic resources, and gene banks become even more valuable [6,7]
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