Genetic variation in grain-filling ability in dwarf pearl millet [Pennisetum glaucum (L.) R. Br.] restorer lines

The d2 dwarfing gene in pearl millet [Pennisetum glaucum] carries a yield penalty due to an associated reduction in individual grain mass. This reduction, however, varies with genetic background, indicating that it may be possible to select against poor grain filling in d2 dwarf backgrounds, given an effective measure of grain filling. This study was conducted to assess genetic variability for grain-filling ability (GFA; in contrast to simply grain size), and its relationship to grain yield, in dwarf pearl millet restorer (R) lines. The GFA of an individual R line was defined as the least squares estimate of its effect on individual grain mass in the analysis of variance, following a linear covariance adjustment for grain number. The study was based on 93 dwarf hybrids involving 31 d2 dwarf R-lines, evaluated over 3 years. Half of the variation in individual grain mass in the 93 hybrids was related to variation in grain number. Covariance adjustment in individual grain mass for grain number resulted in highly significant differences among hybrids and R lines in GFA. The R-line combining ability for GFA accounted for 26% of the variation in the R-line combining ability for yield, compared to 46% for the combining ability for grain number, and just 8% for the combining ability of individual grain mass. The combining ability for GFA was independent of the combining ability for various pre-flowering effects, including grain number, but was related to the combining ability for individual grain mass and harvest index. Improvement in individual grain mass achieved through selection for GFA should translate directly into yield improvement, whereas improvement by direct selection for individual grain mass is less-likely to do so