B Ramaiah

Combining ability and heterosis as influenced by male-sterility inducing cytoplasms in sorghum [Sorghum bicolor (L.) Moench]

An investigation was carried out to assess the efficiency of A2 cytoplasmic-nuclear male-sterility (CMS) system in comparison to the widely used A1 cytoplasm in terms of general combining ability (gca) effects of male-sterile (A-) lines and mean performance, specific combining ability (sca) effects and mid-parent heterosis of hybrids for days to 50% flowering, plant height and grain yield at International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India in 2001 and 2002 rainy seasons. The material for the study consisted of six pairs of iso-nuclear, allo-plasmic (A1 and A2) A-lines and 36 iso-nuclear hybrids produced by crossing these A-lines with three dual restorer (R-) lines. The results revealed that cytoplasm and its first-order interaction with year, R- and A-lines did not appear to contribute to variation in iso-nuclear hybrids for plant height and grain yield. Cytoplasm had limited effect on gca effects of A-lines and on sca effects and mid-parent heterosis of iso-nuclear hybrids for days to 50% flowering, plant height and grain yield. The mean days to 50% flowering, plant height and grain yield of A2 cytoplasm-based hybrids were comparable with those of widely used A1 cytoplasm-based hybrids. The relative frequency of the occurrence of the A1- and A2-based hybrids with significant sca effects and mid-parent heterosis indicated that A2 CMS system is as efficient as A1 with a slight edge over A1 for commercial exploitation. The implications of these results are discussed in relation to opportunities for broadening not only cytoplasm base but also nuclear genetic base of both the hybrid parents.

Options for enhancing grain iron and zinc concentrations in sorghum

INTRODUCTION Micronutrient malnutrition related iron (Fe) and zinc (Zn) deficiencies causes blindness and anemia in more than half of the women and pre‐school children in South and Southeast Asia and sub‐Saharan Africa. Sorghum is cultivated and consumed as a staple food in these areas. Growing high‐yielding cultivars with micronutrient fertilization provides an attractive approach to improve grain micronutrient concentrations (Johnson et al., 2005). ICRISAT Patancheru, India studied the effects of micronutrient fertilization on sorghum grain Fe and Zn concentrations and assessed the genetic variability for grain Fe and Zn concentrations in germplasm and commercial cultivars and the trait associations.