Masumba E A, Kapinga F, Mkamilo G, Salum K, Kulembeka H, Rounsley S, Bredeson J V, Lyons J B, Rokhsar D S, Kanju E, Katari M S, Myburg A A, van der Merwe N A, Ferguson M E
Sugarcane Research Institute, P. O. Box 30031, Kibaha, Tanzania.
Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa.
Theor Appl Genet. 2017 Oct;130(10):2069-2090. doi: 10.1007/s00122-017-2943-z. Epub 2017 Jul 13.
QTL consistent across seasons were detected for resistance to cassava brown streak disease induced root necrosis and foliar symptoms. The CMD2 locus was detected in an East African landrace, and comprised two QTL. Cassava production in Africa is compromised by cassava brown streak disease (CBSD) and cassava mosaic disease (CMD). To reduce costs and increase the precision of resistance breeding, a QTL study was conducted to identify molecular markers linked to resistance against these diseases. A bi-parental F mapping population was developed from a cross between the Tanzanian farmer varieties, Namikonga and Albert. A one-step genetic linkage map comprising 943 SNP markers and 18 linkage groups spanning 1776.2 cM was generated. Phenotypic data from 240 F progeny were obtained from two disease hotspots in Tanzania, over two successive seasons, 2013 and 2014. Two consistent QTLs linked to resistance to CBSD-induced root necrosis were identified in Namikonga on chromosomes II (qCBSDRNFc2Nm) and XI (qCBSDRNc11Nm) and a putative QTL on chromosome XVIII (qCBSDRNc18Nm). qCBSDRNFc2Nm was identified at Naliendele in both seasons. The same QTL was also associated with CBSD foliar resistance. qCBSDRNc11Nm was identified at Chambezi in both seasons, and was characterized by three peaks, spanning a distance of 253 kb. Twenty-seven genes were identified within this region including two LRR proteins and a signal recognition particle. In addition, two highly significant CMD resistance QTL (qCMDc12.1A and qCMDc12.2A) were detected in Albert, on chromosome 12. Both qCMDc12.1A and qCMDc12.2A lay within the range of markers reported earlier, defining the CMD2 locus. This is the first time that two loci have been identified within the CMD2 QTL, and in germplasm of apparent East African origin. Additional QTLs with minor effects on CBSD and CMD resistance were also identified.
检测到对木薯褐色条纹病诱导的根坏死和叶部症状的抗性的QTL在不同季节间是一致的。CMD2位点在一个东非地方品种中被检测到，它包含两个QTL。非洲的木薯生产受到木薯褐色条纹病（CBSD）和木薯花叶病（CMD）的影响。为了降低成本并提高抗性育种的精度，开展了一项QTL研究以鉴定与这些疾病抗性相关的分子标记。一个双亲子代F作图群体由坦桑尼亚农家品种Namikonga和Albert杂交培育而成。构建了一个包含943个SNP标记和18个连锁群、跨度为1776.2厘摩的一步法遗传连锁图谱。2013年和2014年连续两个季节，从坦桑尼亚的两个病害热点地区获得了240个F子代的表型数据。在Namikonga中，在第II号染色体（qCBSDRNFc2Nm）和第XI号染色体（qCBSDRNc11Nm）上鉴定出两个与对CBSD诱导的根坏死抗性相关的一致QTL，在第XVIII号染色体上鉴定出一个推定QTL（qCBSDRNc18Nm）。qCBSDRNFc2Nm在两个季节的纳连代勒均被鉴定到。同一个QTL也与CBSD叶部抗性相关。qCBSDRNc11Nm在两个季节的钱贝齐均被鉴定到，其特征是有三个峰值，跨度为253千碱基对。在该区域内鉴定出27个基因，包括两个富含亮氨酸重复序列（LRR）蛋白和一个信号识别颗粒。此外，在Albert中，在第12号染色体上检测到两个高度显著的CMD抗性QTL（qCMDc12.1A和qCMDc12.2A）。qCMDc12.1A和qCMDc12.2A均位于先前报道的标记范围内，确定了CMD2位点。这是首次在CMD2 QTL内以及明显起源于东非的种质中鉴定出两个位点。还鉴定出了对CBSD和CMD抗性有较小影响的其他QTL。
