Assessment of Cytomorphological Differences in Sorghum Fertility Restoration

Abstract

Sorghum (Sorghum bicolor L. Moench) is ranked fifth as a cereal crop after maize, rice, wheat, and barley based on global cultivation area. However, heat and drought stresses cause improper fertility restoration and inefficient pollination, severely affecting sorghum productivity. The discovery of cytoplasmic male sterility (CMS) is a milestone for commercializing hybrids. This study assessed the pollen fertility and in vitro pollen germination percentage of male and female lines and F1 hybrids of sorghum using two years of pooled data with multivariate analysis. The principal component analysis (PCA) of female and male lines showed that PC1 represented 82.8% of the variation, whereas PCA of hybrids revealed a significant genetic divergence of 97.1%. Agglomerative hierarchical clustering marked that cluster II genotypes have a high pollen fertility contribution, which can generate superior and high-yielding hybrids. Three male-sterile lines exhibited 100% pollen sterility, with morphological attributes, viz., pinpointed, flattened, low anther extrusion, and starch-digested pollens. Pollen fertility restoration behavior revealed that nine hybrids were fully fertile, eighteen were partially fertile, and three were completely sterile amongst thirty hybrids. The findings of this study will facilitate the identification of potential restorers for the exploitation of high-yielding hybrids in sorghum breeding programs.