Fernandes Luciel Dos Santos, Correa Fábio M, Ingram Keith T, de Almeida Alex-Alan Furtado, Royaert Stefan
Mars Center for Cocoa Science, CP 55, Itajuípe, BA CEP 45.630-000 Brazil.
2Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, Rodovia Ilhéus-Itabuna, Km 16, Bairro Salobrinho, Ilhéus, BA CEP 45.662-900 Brazil.
Hortic Res. 2020 Mar 1;7:26. doi: 10.1038/s41438-020-0250-3. eCollection 2020.
Cacao is a crop of global relevance that faces constant demands for improved bean yield. However, little is known about the genomic regions controlling the crop yield and genes involved in cacao bean filling. Hence, to identify the quantitative trait loci (QTL) associated with cacao yield and bean filling, we performed a QTL mapping in a segregating mapping population comprising 459 trees of a cross between 'TSH 1188' and 'CCN 51'. All variables showed considerable phenotypic variation and had moderate to high heritability values. We identified 24 QTLs using a genetic linkage map that contains 3526 single nucleotide polymorphism (SNP) markers. Haplotype analysis at the significant QTL region on chromosome IV pointed to the alleles from the maternal parent, 'TSH 1188', as the ones that affect the cacao yield components the most. The recombination events identified within these QTL regions allowed us to identify candidate genes that may take part in the different steps of pod growth and bean filling. Such candidate genes seem to play a significant role in the source-to-sink transport of sugars and amino acids, and lipid metabolism, such as fatty acid production. The SNP markers mapped in our study are now being used to select potential high-yielding cacao varieties through marker-assisted selection in our existing cacao-breeding experiments.
可可树是一种具有全球重要性的作物，面临着不断提高豆荚产量的需求。然而，对于控制作物产量的基因组区域以及参与可可豆充实过程的基因，我们了解甚少。因此，为了鉴定与可可产量和豆荚充实相关的数量性状位点（QTL），我们在一个由“TSH 1188”和“CCN 51”杂交产生的包含459棵树的分离作图群体中进行了QTL定位。所有变量均表现出相当大的表型变异，并且具有中等到高的遗传力值。我们使用包含3526个单核苷酸多态性（SNP）标记的遗传连锁图谱鉴定了24个QTL。对四号染色体上显著QTL区域的单倍型分析表明，来自母本“TSH 1188”的等位基因对可可产量构成影响最大。在这些QTL区域内鉴定出的重组事件使我们能够鉴定出可能参与豆荚生长和豆粒充实不同阶段的候选基因。这些候选基因似乎在糖和氨基酸的源库运输以及脂质代谢（如脂肪酸生成）中发挥着重要作用。我们研究中定位的SNP标记现在正被用于通过标记辅助选择在我们现有的可可育种实验中筛选潜在的高产可可品种。
