Developmental variability in advanced megagametogenesis and embryogenesis in cultivars of sunflower (Helianthus annuus L.)

MENENDEZ, A.; BIANCHI, M. B.; PICARDI, L.; NESTARES, G.; OCHOGAVÍA, A. C.

CROP SCIENCE

CROP SCIENCE SOC AMER

Año: 2022

0011-183X

In the last few years, some research groups have reported the occurrence of low apospory levels and/or integumentary embryony in wild Helianthus species. Considering the potential impact of apomixis as a tool to optimize plant breeding programs, we aimed at characterizing the reproductive development of nine self-pollinated sunflower cultivars (Helianthus annuus L.) with diverse genetic backgrounds, in order to detect the possible occurrence of aposporyfeatures that would allow future harnessing of maternal reproduction into breeding. Cytoembryological studies were made by DIC microscopy on 1224 clarified ovules from nine genotypes with divergent genetic backgrounds and the seed set was evaluated in an experimental pollination assay. Biometrical parameters of the embryo sac and the endothelial layer were compared by multivariate statistical methods. Significant cyto-embryological variability in the development of female gametophyte was detected and a genotypedependent shape index allowed three embryo sac categories to be recognized. After three seasons of experimental repetition, the qualitative analysis of the developing revealed genotype-dependent endothelial alterations, multiple embryo sac formation possibly related to aposporous-like development, and defective embryo growth during embryogenesis in self-pollinated sunflower lines. Our analysis points to the potential occurrence of apospory and integumentary embryony in H. annuus inbred lines, which is in agreement with previous reports involving wild sunflower species, and reveals four genotypes of cultivated sunflower expressing this ability. These results provide new insights for development of breakthrough breeding strategies in this crop.