Abstract

VALADEZ-GUTIERREZ, Juan et al. Selection for seed size and its effects on seed germination and seedling vigor of sorghum mantainer lines. Agrociencia [online]. 2011, vol.45, n.8, pp.893-909. ISSN 2521-9766.

The first generation of maintainer lines (B-lines) of sorghum (Sorghum bicolor L. Moench) adapted to the Mexican Highlands produced small seeds, which caused a slow growth of seedlings in the field. These lines were crossed to genetic sources of large seed, and after eight cycles of backcrossing to cold tolerant A-lines and visual selection, the second generation of B-lines with a greater seed size was obtained. Six pairs of isogenic A/B lines and their direct and reciprocal A×B crosses representatives of the first generation and eight pairs and their direct and reciprocal A×B crosses representatives of the second generation were evaluated. In the B-lines and in the A×B crosses the average seed weight (PS) and that of its components were calculated: endosperm (PE), embryo (PEM= PS- PE), and the PE: PEM ratio (REE). The seed was subjected to two tests: 1) standard germination, and 2) emergence rate in sand bed. In the sand bed test the length of plumule, radicle and mesocotyl of five seedlings per genotype were also measured, as well as the dry weight of plumule, radicle and seed remnants. Griffing's Method 1 was applied to estimate GCA, SCA and the maternal and reciprocals effects of each diallel array. The PS, PE and PEM of lines of the second generation were greater than those of the first. Heterotic effects for PS and PE were found in both generations. The significant effects of GCA and SCA for PS, PE and REE indicate that selection, in combination with hybridization, increases seed size. The percentage of germination of the lines of the second generation was greater than that of the first in the standard test, but not in the sand bed test. In the variables associated with germination and dry weight of the seedling components or the seedling length, not always high GCA effects corresponded with high SCA effects.

Keywords : maternal effects; seedling establishment; cold tolerance; sorghum parental lines; Sorghum bicolor L. Moench.