Opportunities and challenges in doubled haploids and haploid inducer-mediated genome-editing systems in cucurbits

Abstract

Doubled haploids have played a major role in cucurbit breeding for the past four decades. In situ parthenogenesis via irradiated pollen is the preferred technique in order to obtain haploid plantlets further chromosome doubled in Cucurbitaceae like melon, cucumber, pumpkin, squash and winter squash. In contrast to doubled haploid procedures in other species, in situ parthenogenesis in cucurbits present many limiting factors which impede an efficient production of haploids. In addition, is very time-consuming and labor-intense. However, haploid inducer-mediated genome-editing system is a breakthrough technology for doubled haploid production. CRISPR/Cas9 system have been reported several times in cucurbit species and although its application has many bottlenecks the targeting of CENH3 gene for knock-out will allow breeders to obtain haploid inducer lines further used for parthenogenetic embryo obtention. In this review, we have discussed the progress made towards the development of doubled haploids and haploid inducer genotypes by using CRISPR/Cas9 technologies in cucurbit species. The present review provides insights for the application of haploid inducer-mediated genome-editing system in cucurbit species.