|Graybosch, Robert - Bob|
Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2008
Publication Date: 1/30/2009
Citation: Graybosch, R.A., Baltenspreger, D. 2009. Evaluation of the waxy endosperm trait in proso millet (Panicum mileaceum L.). Plant Breeding 128, 70-73 (2009). Interpretive Summary: Proso millet is a short-seasoned annual grain crop, well adapted to the dry and arid production systems of the western High Plains. It has a very short life-cycle, and the lowest water requirement of any row crop. The states of Colorado, Nebraska and South Dakota together plant about 750,000 acres. Most of the current production of proso millet is used in the wild and domestic bird seed market. In Asia, proso millet also is used for human consumption, where it typically is steam-cooked and eaten in a manner similar to rice. For such applications, consumers favor a “stickier” texture, allowing more easier manipulation by traditional cooking utensils. To achieve this texture, waxy, or amylose-free starch is necessary. All current U.S. cultivars of proso millet are non-waxy, or wild-type. As a step to the development of food-grade proso millets for the U.S., a search was conducted of the USDA germplasm collection to identify waxy types. Only a handful of such types were identified, and all were too late in maturity to be cultivated directly. Breeding efforts are necessary to develop adapted types; such efforts are described elsewhere. As a first step to the successful introgression of any trait, breeders must first understand its inheritance. In this report, the genetics of the waxy trait of proso millet was determined. The identified waxy accessions now may serve a donors for introduction of the trait to U.S. cultivars.
Technical Abstract: The entire USDA-ARS maintained collection of proso millet (Panicum miliaceum L.) was evaluated for the presence of accessions with waxy (amylose-free) endosperm starch. Five accessions, four of which derived from mainland China, were identified. Segregation ratios were evaluated in F2 and F3 populations derived from crosses between two waxy accessions, PI 436625 (Lung Shu 16) and PI 436626 (Lung Shu 18), and several wild-type accessions. The waxy trait was found to be under the control of duplicate recessive alleles at two loci, herein designated wx-1b and wx-2b. Wild-type alleles at these loci were designated Wx-1a and Wx-2a. Iodine-binding revealed a mean grain-starch amylose concentration of 3.5% in waxy lines and 25.3% in wild-type proso. Expression of the granule-bound starch synthase (waxy protein) in waxy lines was reduced to approximately 1/10th that of wild-type accessions. The waxy accessions identified now are available for the introgression of this trait into breeding lines adapted to the Great Plains of North America.