Abstract
Cacao is an important crop, its beans are key raw materials for the chocolate and cosmetic industries. Ceratocystis wilt of cacao (CWC) caused by Ceratocystis cacaofunesta is a lethal disease for the crop. Therefore, the selection of resistant cacao varieties is one of the viable ways to minimize losses in cacao production. In this paper, we described the identification of a major QTL associated with CWC in an F1 mapping population from a cross between a resistant, “TSH 1188,” and a susceptible genotype, “CCN 51.” A set of 266 trees were genotyped using 3,526 single nucleotide polymorphic markers and then multiple QTL mapping analyses were performed. Two QTLs were identified on chromosomes IV and VI. The major QTL was located at 20 cM from the top position of chromosome VI, accounting for more than 60% of the phenotypic variation. The favorable allele T1, with haplotype GTT, came from the “TSH 1188” parent. It was evident that the haplotype combination T1C2 on chromosome VI was the most significant for resistance, since 93% of resistant trees had this haplotype. The major QTL converged to a genomic region of 739.4 kb that harbored nine candidate genes, including two major classes of resistance genes, which would make them the primary candidates involved in the resistance to CWC. The haplotypes detected are now used to improve the efficiency and precision of the selection of resistant trees in cacao breeding.
Highlights
Cacao (Theobroma cacao L.), an allogamous member of the Malvaceae, is indigenous to the Amazon rainforest in South America (Motamayor et al, 2002)
The number of symptomatic plants increased until 28 days after inoculation (DAI) (Figure 1A), when number of dead plants (NDP) was 100%
The best linear unbiased prediction (BLUP) values for NDP in the mapping population ranged from −1.51 to 3.98, whereas the BLUP values for “TSH 1188” and “CCN 51” were −1.51 and 3.95, respectively
Summary
Cacao (Theobroma cacao L.), an allogamous member of the Malvaceae, is indigenous to the Amazon rainforest in South America (Motamayor et al, 2002). Brazilian cacao production has changed slightly over the last 15 years, because the area harvested has increased marginally (FAOSTAT, 2017), and because of abiotic and biotic stresses Concerning these biotic stresses, the incidence of several diseases has contributed to decreased production and has led to even further imbalance in the supply and demand of cacao beans. Cacao trees are constantly confronted with important pathogens that target vegetative shoots, Ceratocystis Wilt Linkage Mapping in Cacao pods and flower cushions (Moniliophthora perniciosa) (Aime and Phillips-Mora, 2005), pods and leaves (Phytophthora spp.) (Barreto et al, 2015; Surujdeo-Maharaj et al, 2016), and the vascular system (Ceratocystis cacaofunesta) (Engelbrecht and Harrington, 2005) Of these diseases, Ceratocystis wilt of cacao (CWC) is one the most important, mainly because it causes plant death. Most progenies from this cross were susceptible to CWC disease, which led to a drastic reduction in cacao production in Bahia, Brazil (Lopes et al, 2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
