Significant Parent-of-Origin Effects for Seed, Cotyledon, and Early Plant Growth Traits in Cucumber

Abstract

Parent-of-origin effects have long been recognized and exploited in plant breeding and genetic studies. These effects can be conferred by preferential expression of an allele from one parent, organellar effects, or altered organellar-nuclear interaction. The goal of this work was to evaluate parent-of-origin effects on seed, cotyledon, and early growth traits in cucumber using a full eight-by-eight diallel from crossing two doubled haploids (DHs) extracted from each of four cucumber populations. Significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were observed for all traits, and direction and magnitude of effects were DH rather than population specific. Transcriptome analyses of reciprocal hybrids with and without significant reciprocal effects for early plant growth revealed that different pathways were associated with the significant reciprocal differences. These findings are consistent with the DH-specific nature of combining abilities and reciprocal effects across cucumber populations. Because reciprocal effects were DH and hybrid-combination specific, cucumber breeders should generate and evaluate both hybrids from reciprocal crossing for improved hybrid development.