Phenotypic Description of Theobroma cacao L. for Yield and Vigor Traits From 34 Hybrid Families in Costa Rica Based on the Genetic Basis of the Parental Population

Abstract

A comprehensive understanding of the genetic basis of target traits in any crop is critical to design breeding strategies for the development and release of new improved varieties. In this study, 34 cacao families were evaluated for vigor and yield related traits over the course of 6 years in Costa Rica. Linear mixed models provided the variance components for the partitioning of additive and non-additive effects. Heritabilities of yield over time ranged from 0.085 to 0.576, from 0.127 to 0.399 for vigor, and 0.141 to 0.146 for disease resistance traits. Significant (p < 0.001) general combining abilities were observed for ICS-43 and LcTeen-37 with negative effect on average yield (−0.674, −0.690), respectively. Specific combining abilities for yield had significant (p < 0.001) positive effect from the cross GU-154-L x UF-273 Type 2 (0.703) and strong negative interaction between ICS-43 and LF-1 (−0.975). A weighted index was used to select the top performers while providing the corresponding genetic gains. At an 1% selection intensity, yield component gains ranged from 17.8 to 331.9%. Agronomic traits such as branch angle, trunk diameter and jorquette height had lower genetic gains and lower heritabilities. In addition, the parents in this study were genotyped with a 96-SNP marker off-typing set and a significant positive correlation of 0.39 (p = 0.019) was found between genetic distance and specific combining abilities for yield. Preliminary comparison of clonal parents vs. seedlings yield in the family with the highest SCA suggest for the first time presence of heterobeltiosis in cacao.

Identification of Climate and Genetic Factors That Control Fat Content and Fatty Acid Composition of Theobroma cacao L. Beans

“…Most traits for which estimates of heritability have been reported (Ndoumbé et al, 2001; Lockwood et al, 2007; Cilas et al, 2010; Ofori et al, 2016; DuVal et al, 2017; Mustiga et al, 2018; Padi et al, 2017; Romero Navarro et al, 2017) show a range between 0.13 and 0.79. Heritabilities calculated for the FA content in this study ( Table 7 ) also varied within that range (0.14–0.43).…”

Assessment of Heterosis Based on Parental Genetic Distance Estimated With SSR and SNP Markers in Upland Cotton (Gossypium Hirsutum L.)

“…Signi cant correlation was observed between GD and MPH of plant height, gross plant weight, net curd weight, leaf width, curd diameter and total marketable yield in Brassica oleracea [25]. In cacao, a signi cant positive correlation of 0.39 was found between GD and SCA for yield [26]. Studies in rapeseed showed that GD evaluated by total molecular markers (GD total ) had no correlation with heterosis but GD measured by favoring markers (GD favor ) signi cantly and positively correlated with the number of seeds per silique, thousand seed weight, seed yield per plant and seed yield per plot for high-check heterosis and sum of parental general combining ability [29].…”

“…Earlier at the end of the 20th century, some studies have used RFLP and SSR markers to study the relationship between GD and heterosis, and proposed that the relationship between GD and heterosis could be predicted by genetic differences [17]. Subsequently, a number of studies used RAPD [18], AFLP [19,20], SSR [21][22][23], EST-SSR [24,25], InDel [11] and SNP markers [13,[26][27][28] to study the relationship between GD and heterosis. Previous studies used different molecular marker types and those results were also different, but the GD was not compared.…”

QTL mapping and identification of SNP-haplotypes affecting yield components of Theobroma cacao L.

“…The pod index (PI), which is defined as the number of pods required to obtain 1 kg of dry bean weight, was calculated as PI = NHPH × 1000/FBW × 0.36. The calculations were based on Mustiga et al 54 , with modifications in fresh to dry bean weight conversation factor, as explained above. We also calculated the single dry bean weight (DBW), which was calculated as DBW = FBW × 0.36/total number of beans per pod.…”