Exploring candidate genes related to pollen abortion in garlic (Allium sativum) based on cytological studies and transcriptome sequencing.

Abstract

The commercially cultivated garlic varieties are infertile, leading to challenges in conventional hybrid breeding. Xinjiang garlic exhibits visually normal development of both androecium and gynoecium, but most pollen grains are not viable, thus allowing for the identification of flower development-related genes through combined morphological, anatomical, and cytological methods with transcriptome analysis. The inflorescence meristem differentiation of Xinjiang garlic plants was initiated after the 6th-7th leaves emerged, implying the transition from vegetative growth to reproductive growth. With the development of flower organs after bolting, normal pollen mother cell meiosis but no viable pollen grains were detected through triphenyl tetrazolium chloride (TTC) staining. Delayed tapetal degeneration, the gap between the tapetum and the middle layer, and degenerating and aborting anther are visible during anther development. There were 25 differentially expressed MYB genes and 64 flowering pathway related genes at different stages of flower development. The R2R3-MYB genes enriched in Module 22 are involved in the development of the tapetum and pollen. The co-expression network analysis showed that most MYB genes are related to flowering regulatory genes. The expression pattern of MYB35, MYB26, MYB80 and MMD1 may cause delayed degradation of the tapetum, or abnormal development of the pollen wall leading to pollen abortion.