Dorji Kinley, Yapwattanaphun Chinawat
Department of Agriculture, Renewable Natural Resources Research and Development Center, Bajo, Wangduephodrang, Bhutan.
Department of Horticulture, Kasetsart University, Bangkok, 10900, Thailand.
BMC Genet. 2015 Apr 18;16:39. doi: 10.1186/s12863-015-0198-8.
Bhutan is a small Himalayan country lying within the region considered to be the origin of citrus. Diverse citrus wild types grow naturally in different climates, elevations and edaphic conditions, but only mandarin is cultivated commercially. The first report of Huanglongbing (also known as greening disease) in Bhutan in 2003, and the threat it posed to the country's citrus orchards prompted the collection of mandarin germplasm from across the country. This paper describes the genetic diversity of mandarin accessions in Bhutan using amplified fragment length polymorphic (AFLP) markers.
Twenty three accessions of Bhutanese mandarin were analyzed using AFLP markers to assess the genetic variability that is believed to exist only in Bhutan and some parts of North East India and South China. Five primer pairs (E-ACA/M-CAG, E-ACG/M-CAT, E-ACC/M-CTT, E-AAG/M-CAA and E-ACA/M-CTC) were identified (based on the number and quality of polymorphic bands produced) and used for the analyses. A total of 244 bands were scored visually of which 126 (52%) were polymorphic with an average polymorphism information content of 0.95 per marker. A cluster dendrogram based on multiscale bootstrap sampling categorized twenty three accessions into two broad groups containing eight and 14 accessions, respectively. Group A consisted accessions (Tsirang1, Tsirang3, Sarpang1, Dagana4, Samtse4, Dagana1, and Trongsa2) from five districts (Tsirang, Sarpang, Samtse, Dagana and Trongsa) and their grouping was strongly supported by bootstrap analysis (B p-value = 96%, AU p-value = 86%). Cluster B consisted of 14 accessions divided into three sub-groups (1, 2 and 3). However, bootstrap value supported significantly for subgroup1 (containing accessions: Tsirang4, Sarpang5, and Tsirang2) and subgroup3 (with accessions - Zhemgang2, Zhemgang3 and Zhemgang4).
This study indicates that Bhutanese mandarin germplasm collected from across the country are genetically diverse although the level of variability differed among the accessions assessed. The variation in genetic variability was observed irrespective of where the accessions were collected suggesting that phenotype and geographical location can serve a basis for future germplasm collection in Bhutan. Further, five primer pair combinations could separate 23 mandarins accessions considered in this study, suggesting that AFLP markers can be a useful tool for future identification.
不丹是一个位于喜马拉雅山脉的小国，处于被认为是柑橘起源的地区。多种柑橘野生类型在不同的气候、海拔和土壤条件下自然生长，但只有柑橘被商业化种植。2003年不丹首次报告黄龙病（也称为柑橘绿霉病），以及该病对该国柑橘园构成的威胁，促使人们从全国各地收集柑橘种质。本文使用扩增片段长度多态性（AFLP）标记描述了不丹柑橘种质的遗传多样性。
使用AFLP标记对23份不丹柑橘种质进行分析，以评估据信仅存在于不丹以及印度东北部和中国南部部分地区的遗传变异性。根据产生的多态性条带的数量和质量，鉴定出五对引物（E-ACA/M-CAG、E-ACG/M-CAT、E-ACC/M-CTT、E-AAG/M-CAA和E-ACA/M-CTC）并用于分析。共目视评分244条带，其中126条（52%）为多态性条带，每个标记的平均多态性信息含量为0.95。基于多尺度自展抽样的聚类树状图将23份种质分为两大组，分别包含8份和14份种质。A组由来自五个地区（齐朗、萨尔庞、萨姆奇、达加纳和通萨）的种质（齐朗1、齐朗3、萨尔庞1、达加纳4、萨姆奇4、达加纳1和通萨2）组成，自展分析强烈支持它们的分组（B p值 = 96%，AU p值 = 86%）。B组由14份种质组成，分为三个亚组（1、2和3）。然而，自展值对亚组1（包含种质：齐朗4、萨尔庞5和齐朗2）和亚组3（包含种质 - Zhemgang2、Zhemgang3和Zhemgang4）有显著支持。
本研究表明，从全国各地收集的不丹柑橘种质在遗传上具有多样性，尽管在所评估的种质中变异水平有所不同。无论种质采自何处，均观察到遗传变异性的差异，这表明表型和地理位置可为不丹未来的种质收集提供依据。此外，五对引物组合能够区分本研究中考虑的23份柑橘种质，这表明AFLP标记可成为未来鉴定的有用工具。
