|Graybosch, Robert - Bob|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 8/10/2004
Publication Date: 10/1/2004
Citation: Graybosch, R.A., Baltensperger, D.D. 2004. Evaluation of the waxy endosperm trait of proso millet. ASA-CSSA-SSSA Annual Meeting Abstracts. CD-ROM No. 4188. Interpretive Summary:
Technical Abstract: A survey of the USDA-ARS proso millet germplasm collection led to the discovery of six accessions with waxy ('amylose-free') starch. Crosses were obtained between two waxy accessions (PI 436625 and PI 436626) and several wild-type cultivars and land-races. In all combinations but one, F2 and F3 segregation ratios indicated the waxy trait was conditioned by recessive alleles at two independent loci. In crosses with the wild-type accession PI 346945, however, monogenic inheritance was indicated. It is hypothesized that most wild-type proso millets contain dominant genes at two waxy loci, but PI 346945 carries a recessive gene at one of these loci. Similar situations have been observed with waxy alleles of other tetraploid crops including durum and common wheat. Grain starch amylose content of waxy segregants ranged from 1.3 to 5.1%, with a mean of 3.5%, as opposed to mean amylose contents in wild-type lines of 25.3%. Granule-bound starch synthase, the enzyme responsible for amylose synthesis, was detected in waxy starch granules, but its abundance was reduced to approximately 10% that of wild-type lines. It is hypothesized that at least one of the recessive waxy alleles of proso millet produces some granule-bound starch synthase. Whether the low levels of amylose observed in the waxy lines are due to low levels of enzyme activity, or merely reflect the well-known low level of iodine binding by amylopectin, has not been determined.