Field evaluation of cacao progenies derived from Guiana clones for yield and black pod disease resistance

Abstract

Phytophthora spp. is a major disease of cacao (Theobroma cacao L.), and there is a need to develop cultivars that are resistant to this disease. Among the various genetic groups of cacao, the Guiana (GU) has received little attention in developing varieties even though they are known to be tolerant to black pod disease. The objective of this study was to estimate combining abilities and heritability of selected GU clones for bean yield and black pod resistance. Twenty‐four F1 progenies were derived by crossing three seed garden parental clones with eight GU clones as males in a three‐by‐eight North Carolina II (NC II) complete factorial mating design. These were evaluated together with four standard varieties over a 4‐yr period in a randomized complete block design with four replications at two contrasting locations in Ghana. Progeny, year, and location effects were significant (p < .01) for all traits, whereas progeny × location was significant for only number of beans per pod. The general combining ability (GCA) effects of females and males and specific combining ability (SCA) of female × male were significant (p < .01) for all traits, indicating that both additive and dominant effects are important in the inheritance of the traits. Heritability ranged from 0.14–0.51 for broad sense and 0.10−0.37 for narrow sense. The best general combiners identified—GU 125/C, GU 144/C, and GU 290/H—were involved in crosses that combines high bean yield with high black pod resistance. They could be added to parental clones currently used in producing cacao varieties in areas with high black pod incidence.

Geographic distribution, conservation, and genomic resources of cacao Theobroma cacao L

“…Some cacao natural populations and cultivars show resistance to BPR, as well as disease resistance candidate genes are also identified (Table 1). For example, the Guiana group showed natural resistance to P. megakarya : Disease resistance was evaluated using artificial inoculation with P. megakarya in detached cacao leaves (Paulin et al., 2008), and the resistance of Guiana progenies to BPR was confirmed in field evaluations in Ghana (Ofori et al., 2020). Field evaluation of 148 individuals with admixed ancestry showed that trees with higher Nacional ancestry were more susceptible to BPR, whereas those with Marañon ancestry showed resistance to BPR (Romero‐Navarro et al., 2017).…”

“…These findings provide evidence of natural resistance to BPR among wild cacao populations. Incorporation of disease resistance while including additional traits, such as higher yield in single genotypes, still remains a challenge for breeding programs, but progress has been made in West Africa (Ofori et al., 2020) and Tropical America (Gutiérrez et al., 2016; Gutiérrez, Puig, et al., 2021; Phillips‐Mora et al., 2012).…”