Diallel genetic analysis for multiple traits in eggplant and assessment of genetic distances for predicting hybrids performance

Evaluation and prediction of the performance of hybrids is important in eggplant (Solanum melongena) breeding. A set of 10 morphologically highly diverse eggplant parents, including nine inbred S. melongena and one weedy S. insanum accessions, were intercrossed according to a half-diallel mating design without reciprocals to obtain 45 hybrids. Parents and hybrids were evaluated for 14 morphological and agronomic conventional descriptors and 14 fruit morphometric traits using Tomato Analyzer. Genetic distances among parents were estimated with 7,335 polymorphic SNP markers. Wide ranges of variation and significant differences were observed in the set of 55 genotypes for all traits, although the hybrids group had significantly higher vigour and yield than parents. General and specific combining abilities (GCA and SCA) were significant for most (GCA) or all (SCA) traits, although a wide variation was obtained for GCA/SCA ratios. Many relevant traits associated to vigour and yield had low GCA/SCA ratios and narrow-sense heritability (h2) values, while the reverse occurred for most fruit shape descriptors. Broad-sense heritability (H2) values were generally high, irrespective of GCA/SCA ratios. Significant correlations were found between traits related to size of leaf, flower and fruit, as well as among many fruit morphometric traits. Genetic distances (GD) among parents were coherent with their phylogenetic relationships, but few significant and generally low correlations were found between GD and hybrid means, heterosis or SCA. The results provide relevant information for developing appropriate strategies for parent selection and hybrid development in eggplant and suggest that GD among parents have limited value to predict hybrid performance in this crop.

茄子（Solanum melongena）育种中，杂交组合表现的评估与预测具有重要意义。本研究选取10个形态学差异显著的茄子亲本，包括9个栽培茄（S. melongena）自交系与1个野生茄（S. insanum）种质，采用半双列杂交设计（无反交）进行组配，共获得45个杂交组合。对亲本及杂交组合，采用Tomato Analyzer（番茄分析仪）鉴定评价14项形态学与农艺学常规性状，以及14项果实形态计量学性状；利用7335个多态性SNP标记估算亲本间的遗传距离。供试的55份基因型材料在所有性状上均表现出广泛的变异幅度与极显著差异，其中杂交组合群体的长势与产量均显著高于亲本群体。多数性状的一般配合力（GCA）、全部性状的特殊配合力（SCA）均达显著水平，但GCA/SCA比值存在广泛变异。与长势、产量相关的多数重要性状的GCA/SCA比值与狭义遗传力（h²）均较低，而多数果实形状性状则呈现相反结果。无论GCA/SCA比值如何，广义遗传力（H²）整体均处于较高水平。叶、花、果大小相关性状间，以及多数果实形态计量学性状间均存在显著相关性。亲本间的遗传距离（GD）与其系统发育关系基本一致，但遗传距离与杂交组合均值、杂种优势或特殊配合力之间仅存在少量显著且相关性普遍较低的关联。本研究结果可为茄子育种中亲本选择与杂交组合培育的合理策略制定提供重要参考，同时表明亲本间的遗传距离在该作物中对杂交组合表现的预测价值有限。