Ana Luísa Garcia-Oliveira, Bernadetha Kimata, Salum Kasele, Fortunus Kapinga, Esther Masumba, Geoffrey Mkamilo, Caroline Sichalwe, Jessen V Bredeson, Jessica B Lyons, Trushar Shah, Satoru Muranaka, Manpreet S Katari, Morag E Ferguson.

PLoS One. 2020 Aug 5; 15(8):e0236674.  doi: 10.1371/journal.pone.0236674. eCollection 2020.

Abstract

In Sub-Saharan Africa cassava (Manihot esculenta Crantz) is one of the most important food crops where more than 40% of the population relies on it as their staple carbohydrate source. Biotic constraints such as viral diseases, mainly Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD), and arthropod pests, particularly Cassava Green Mite (CGM), are major constraints to the realization of cassava's full production potential in Africa. To address these problems, we aimed to map the quantitative trait loci (QTL) associated with resistance to CBSD foliar and root necrosis symptoms, foliar CMD and CGM symptoms in a full-sib mapping population derived from the genotypes AR40-6 and Albert. A high-density linkage map was constructed with 2,125 SNP markers using a genotyping-by-sequencing approach. For phenotyping, clonal evaluation trials were conducted with 120 F1 individuals for two consecutive field seasons using an alpha-lattice design at Chambezi and Naliendele, Tanzania. Previously identified QTL for resistance to CBSD foliar symptoms were corroborated, and a new putative QTL for CBSD root necrosis identified (qCBSDRNc14AR) from AR40-6. Two QTL were identified within the region of the previously recognized CMD2 locus from this population in which both parents are thought to possess the CMD2 locus. Interestingly, a minor but consistent QTL, qCGM18AR, for CGM resistance at 3 months after planting stage was also detected and co-localized with a previously identified SSR marker, NS346, linked with CGM resistance. Markers underlying these QTL may be used to increase efficiencies in cassava breeding programs.

See: https://pubmed.ncbi.nlm.nih.gov/32756600/

Figure 3: Chromosome XII linkage map showing the position of QTL identified in the present investigation in relation to the previously reported SSR markers; SSRY28, SSRNS158 and SSRNS169 (CMD2) and NS198 (CMD3) associated with CMD resistance loci in cassava.

Trait nomenclature was named in combination of the disease, stage, location and year such as Cassava Mosaic Disease (CMD), 3 or 6 months after planting (3 MAP or 6 MAP) stage, crop season 2013 or 2014 at location Naliendele (NAL13 or NAL14) and Chambezi (CHA13 or CHA14), whereas pooled represents average of the trait from four environments either at 3 or 6 MAP stage.