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Title: A legume biofortification quandary: Variability and genetic control of seed coat micronutrient accumulation in common beans

item BLAIR, MATTHEW - Cornell University - New York
item IZQUIERDO, PAULO - Centro Nacional De Investigacion En Cana (CENICANA)
item ASTUDILLO, CAROLINA - Michigan State University
item Grusak, Michael

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2013
Publication Date: 7/29/2013
Citation: Blair, M.W., Izquierdo, P., Astudillo, C., Grusak, M.A. 2013. A legume biofortification quandary: Variability and genetic control of seed coat micronutrient accumulation in common beans. Frontiers in Plant Science. 4:275.

Interpretive Summary: Dry beans are an important food source that can provide protein, energy in the form of starch, and several human-essential minerals, including iron. Because of the importance of iron in human health, our goal has been to find ways to increase the concentration of iron in plant food crops such as dry bean, to help ensure that consumers meet their daily intake requirements for this mineral. In this study, we investigated genetic factors that control the distribution of iron in bean seeds. Previous work has shown that iron concentration is higher in the dry bean's seed coat, relative to the cotyledon and embryo axis tissues within that seed coat. We measured mineral concentrations in seed coats of individual bean types that were part of a unique population of bean plants. This population was derived from a wild bean and a cultivated bean. A broad range of mineral concentrations was found in the seed coats of the plants from this population. We were able to use these results to identify regions of the bean plant's chromosomes (i.e., DNA segments) that were associated with elevated iron concentrations in seed coats. This information will help us identify genes that control iron distribution and concentrations in seeds. It will also provide tools for breeders to develop nutritionally improved cultivars of dry beans.

Technical Abstract: Common beans (Phaseolus vulgaris L.), like many legumes, are rich in iron, zinc, and certain other microelements that are generally found to be in low concentrations in cereals, other seed crops, and root or tubers, and therefore are good candidates for biofortification. But a quandary exists in common bean biofortification: namely that the distribution of iron has been found to be variable between the principal parts of seed, namely the cotyledonary tissue, embryo axis, and seed coat. The seed coat represents 10 or more percent of the seed weight and must be considered specifically, as it accumulates much of the anti-nutrients such as tannins that affect mineral bioavailability. Meanwhile the cotyledons accumulate starch and phosphorus in the form of phytates. The goal of this study was to evaluate a population of progeny derived from an advanced backcross of a wild bean and a cultivated Andean bean for seed coat versus cotyledonary minerals to identify variability and predict inheritance of the minerals. We used wild common beans because of their higher seed mineral concentration compared to cultivars and greater proportion of seed coat to total seed weight. Results showed the most important gene for seed coat iron was on linkage group B04, but also identified other QTL for seed coat and cotyledonary iron and zinc on other linkage groups, including B11 which has been important in studies of whole seed. The importance of these results in terms of physiology, candidate genes, and plant breeding are discussed.