Inheritance of Seedling Hydrocyanic Acid Potential and Seed Weight in Sorghum‐Sudangrass Crosses¹

Abstract

The hydrocyanic acid potential (HCN‐p) of sorghum [Sorghum bicolor (L.) Moench] plants is recognized as a heritable trait, but previous studies on the mode of inheritance of HCN‐p have produced inconsistent results. The objective of this study was to investigate the inheritance patterns of seedling HCN‐p and also of seed weight in reciprocal crosses of sorghum and sudangrass [formerly S. sudanense (Piper) Stapf]. Both traits were found to be inherited quantitatively. Generation means analysis indicated that additive genetic effects were most important for both seed weight (53% of variation) and seedling HCN‐p (74% of variation). A maternal effect was found for both traits in the F1 and backcross generations. No evidence of this reciprocal effect was found in the F2, suggesting that cytoplasmic inheritance was not involved. A highly positive correlation between seed weight and HCN‐p was found across all entries, across both parents, and in the F1 and backcross generations. However, correlation coefficients between seed weight and seedling HCN‐p for individual entries, the pooled F2'S, or within types of seed parents in the F1 or backcross generations were generally nonsignificant. It was concluded that seed weight per se does not have a large effect on seedling HCN‐p.

Identification of Chromosomes that Condition Dhurrin Content in Sorghum Seedlings1

“…These results are consistent with previous studies (2,3,8,10) in which it was concluded that the inheritance of HCN-p in sorghum was multigenic. Even more than five allelic pairs may be involved because some of the limitations in the use of chromosomal translocations for determining the number of genes conditioning a character, as described by Scott et al (14), also would apply in the present study.…”

Seed Weight Influence on Seedling Hydrocyanic Acid Potential in Sorghum

“…Means for both first-leaf and shoot-remainder HCN-p showed the same sort of seed-parent influence as that previously observed by Lamb et al (1987); that is, values for sorghum X sudangrass hybrids were higher than those for sudangrass X sorghum hybrids. This was true of seedlings from both small and large seeds.…”

“…Also, seeds from the sudangrass X sorghum crosses were smaller and seedlings were lower in HCN-p than corresponding seeds and seedlings from sorghum X sudangrass hybrids. The mean comparisons discussed previously and the correlations within and across entries all verify the previous research of Lamb et al (1987), which indicated that when seeds are identical with respect to genotype of both endosperm and embryo, seed weight has little if any effect on seedling HCN-p. Therefore, it is reasonable to infer than the seed-parent effect on seedling HCN-p in crosses of sorghum and sudangrass was not due primarily to the seed-parent effect on seed weight.…”

“…When all entries were considered together (overall phenotypic values, Table 2) a strong relationship between seed weight and HCN-p was apparent. As pointed out by Lamb et al (1987) and as verified by the data in Table 1, this may be attributed to the fact that the sorghum entries had larger seeds and higher seedling HCN-p values than the sudangrass entries. Also, seeds from the sudangrass X sorghum crosses were smaller and seedlings were lower in HCN-p than corresponding seeds and seedlings from sorghum X sudangrass hybrids.…”

“…Reciprocal sorghum X sudangrass hybrids included the following: 1901 X BCK60, ACK60 X 1901, 1901X BRedlan, ARedian X 1901, 1904X BCK60, ACK60 X 1904, 1904X BRedlan, and ARedlan X 1904. Further descriptions of the parental lines and the crosses used to produce the F 1 hybrids are given by Lamb et al (1987).…”