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Purdue University (2015)

Mapping and Identification of Increased Protein Digestibility in Sorghum

Massafaro, Moriah M

Titre : Mapping and Identification of Increased Protein Digestibility in Sorghum

Auteur : Massafaro, Moriah M

Université de soutenance : Purdue University

Grade : Master of Science (MS) 2015

Sorghum (Sorghum bicolor [L.] Moench) is the world’s fifth most important cereal crop and a dietary staple for approximately 500 million people in over 30 countries of the Semi-Arid Tropics. Unlike other major cereals such as maize, sorghum becomes much less digestible after it is cooked in the presence of water, often providing as little as 20% of the available protein to the consumer. Digestibility appears to be under genetic control, although the specific details remain unclear. The goals of these studies were to identify sorghum cultivars that do not show this large decrease in digestibility after cooking and to determine the genetic controls of increased digestibility in a previously identified sorghum mutant, P721Q.^ The high lysine sorghum mutant, P721Q, identified 30 years ago, exhibits a 3- to 4-fold increase in protein digestibility after cooking as compared to other sorghum cultivars, which makes it even more valuable as a food staple. However, this cultivar has a floury endosperm type, which is undesirable for storage and for food products. The cause of the increased digestibility for P721Q is likely a kafirin (prolamin) mutation. This determination was made using bulked segregant analysis for a mapping population for P721Q and a high-throughput sorghum protein digestibility assay.^ This sorghum protein digestibility assay was also utilized to classify an ethyl methanesulfonate (EMS) mutant population of sorghum (600 sequenced and 4,000 non-sequenced individuals) and a sorghum diversity set (53 cultivars). Three highly digestible EMS individuals were identified that had a protein digestibility that was equal to or exceeded that of P721Q. None of the cultivars in the diversity set were highly digestible. These findings and past literature suggest that there is not a naturally occurring sorghum cultivar that possesses high protein digestibility. One of the EMS mutants was tested for seed hardness and was found to be harder than P721Q. All three highly digestible EMS individuals have been crossed to elite African cultivars to improve the nutrition of sorghum.


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