Genetic diversity and structure of Musa balbisiana populations in Vietnam and its implications for the conservation of banana crop wild relatives

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.

Assessment of genetic diversity and volatile content of commercially grown banana (Musa spp.) cultivars

“…The genetic diversity of bananas has been carried out using different molecular markers, and significant success has been made for analyzing commercial cultivars and some wild germplasm 34 , 35 . However, not much is known about the local germplasm, which harbors important traits for adaptation to local climatic conditions and small-holdings.…”

Phylogeography and conservation gaps of Musa balbisiana Colla genetic diversity revealed by microsatellite markers

“…From all assessed microsatellite loci, BB_CT-33, BB_GAA-4, BB_CT-6, and BB_CT-8 were the most informative. While five loci were uninformative (monomorphic) for the samples included in this study (Mbg02, Mbg04, BB_AAC-3, BB_CT-7, and Mbg01), they were retained for all analyses in order to be able to compare results with the studies of Bawin et al ( 2019 ) and Mertens et al ( 2021a ). The proportion of polymorphic loci ( %P ) and average number of different alleles ( Na ) ranged from 0 to 66.67 and 1.000 to 2.167 respectively (Table 1 ).…”

“…A previous study of Mertens et al ( 2021a ) demonstrated that Chinese and northern Vietnamese populations contained high genetic diversity which is important to conserve while additional sampling in Central Vietnam was recommended based on the high genetic diversity and number of unique alleles in the two sampled populations. Vietnamese populations could be distinguished from Chinese populations, with even further substructuring of Vietnamese populations at higher K -values.…”

“…Musa balbisiana samples from different countries were acquired from three different sources (Supplementary Information – Table 1). Firstly, SSR data of Musa balbisiana were retrieved from two previous studies (Bawin et al 2019 ; Mertens et al 2021a ). Secondly, 28 different germplasm accessions of M. balbisiana from the ITC (one sample per accession) originating from the Philippines, Indonesia, India, PNG, China, and Thailand were included (Fig.…”

“…We used the same set of 18 microsatellite markers arranged in four multiplexes as described in Bawin et al ( 2019 ) to compare the ITC samples with those used in Bawin et al ( 2019 ) and Mertens et al ( 2021a ). Markers were coupled to universal primer sequences (Schuelke 2000 ) and DNA fragments were amplified with PCR using the Type-it Microsatellite PCR Kit (Qiagen, Venlo, The Netherlands).…”