National Root Crops Research Institute, NRCRI, Umudike, Nigeria.
International Institute for Tropical Agriculture (IITA), Ibadan, Nigeria.
PLoS One. 2020 Apr 2;15(4):e0231008. doi: 10.1371/journal.pone.0231008. eCollection 2020.
Cassava green mite [CGM, Mononychellus tanajoa (Bondar)] is the most destructive dry-season pest in most cassava production areas. The pest is responsible for cassava fresh root yield losses of over 80%. Deployment of CGM resistant cultivars is the most cost-effective and sustainable approach of alleviating such production losses. The purposes of this study were to validate the stability of CGM resistance genes found in previously published results, to identify new genes for CGM resistance in bi-parental mapping population and estimate the heritability of the trait. A total of 109 F1 progeny derived from a cross between CGM resistant parent, TMEB778 and a very susceptible parent, TMEB419 were evaluated under CGM hotspot areas in Nigeria for two cropping seasons. A total of 42,204 SNP markers with MAF ≥ 0.05 were used for single-marker analysis. The most significant QTL (S12_7962234) was identified on the left arm on chromosome 12 which explained high phenotypic variance and harboured significant single nucleotide polymorphism (SNP) markers conferring resistance to CGM and leaf pubescence (LP). Colocalization of the most significant SNP associated with resistance to CGM and LP on chromosome 12 is possibly an indication of a beneficial pleiotropic effect or are physically linked. These significant SNPs markers were intersected with the gene annotations and 33 unique genes were identified within SNPs at 4 - 8MB on chromosome 12. Among these genes, nine novel candidate genes namely; Manes.12077600, Manes.12G086200, Manes.12G061200, Manes.12G083100, Manes.12G082000, Manes.12G094100, Manes.12G075600, Manes.12G091400 and Manes.12G069300 highly expressed direct link to cassava green mite resistance. Pyramiding the new QTL/genes identified on chromosome 12 in this study with previously discovered loci, such on chromosome 8, will facilitate breeding varieties that are highly resistant CGM.
木薯叶甲 [CGM，Mononychellus tanajoa（Bondar）] 是大多数木薯种植区破坏性最大的旱季害虫。该害虫导致木薯鲜根产量损失超过 80%。部署对木薯叶甲具有抗性的品种是缓解此类生产损失的最具成本效益和可持续的方法。本研究的目的是验证先前研究结果中发现的对木薯叶甲具有抗性的基因的稳定性，在双亲作图群体中鉴定对木薯叶甲具有抗性的新基因，并估计该性状的遗传力。在尼日利亚的木薯叶甲热点地区，用两年的时间对 109 个来自对木薯叶甲具有抗性的亲本 TMEB778 和非常敏感的亲本 TMEB419 的杂交后代进行了评估。总共使用了 42204 个 MAF≥0.05 的 SNP 标记进行单标记分析。在第 12 号染色体的左臂上鉴定到一个最显著的 QTL（S12_7962234），该 QTL 解释了高表型方差，并携带显著的单核苷酸多态性（SNP）标记，赋予对木薯叶甲和叶片刚毛（LP）的抗性。在第 12 号染色体上与对木薯叶甲和 LP 的抗性最显著的 SNP 发生共定位，这可能表明存在有益的多效性效应或物理连锁。这些与对木薯叶甲和 LP 的抗性相关的显著 SNP 标记与基因注释相交，并在第 12 号染色体上的 4-8MB 处鉴定到 33 个独特的基因。在这些基因中，鉴定到 9 个新的候选基因，即 Manes.12077600、Manes.12G086200、Manes.12G061200、Manes.12G083100、Manes.12G082000、Manes.12G094100、Manes.12G075600、Manes.12G091400 和 Manes.12G069300，这些基因高度表达并与对木薯叶甲的抗性直接相关。在本研究中在第 12 号染色体上鉴定到的新 QTL/基因与之前在第 8 号染色体上发现的基因进行聚合，将有助于培育对木薯叶甲具有高度抗性的品种。
