Abstract
Foxtail millet (Setaria italica (L.) P. Beauv.), the second most cultivated millet species, is well adapted to diverse environments and remains an important cereal food and forage crop in arid and semiarid regions worldwide. A symbolic crop for indigenous Austronesian peoples, foxtail millet has been cultivated in Taiwan for more than 5,000 years, and landraces reflect diversifying selection for various food applications. A total of 124 accessions collected within Taiwan were assessed for Wx genotypes. Four identified Wx alleles, I, III, IV, and IX were caused by insertion of various transposable elements (TEs) and resulted in endosperm with non-waxy, low amylose content (AC), and waxy, respectively. A total of 16.9%, 4.0%, 49.2%, and 29.8% of accessions were classified as type I, III, IV, and IX, respectively; approximately half of the accessions belonged to the waxy type, indicating that glutinous grains were favored for making traditional food and wine. The TE insertion affected splicing efficiency rather than accuracy, leading to significantly reduced expression of wx in types III, IV, and IX, although their transcripts were the same as wild-type, type I. Consequently, the granule-bound starch synthase I (GBSSI) contents of the three mutated genotypes were relatively low, leading to waxy or low AC endosperm, and the Wx genotypes could explain 78% of variance in AC. The geographic distribution of Wx genotypes are associated with culinary preferences and migration routes of Taiwanese indigenous peoples—in particular, the genotype of landraces collected from Orchid Island was distinct from those from Taiwan Island. This information on the major gene regulating starch biosynthesis in foxtail millet endosperm can be applied to breeding programs for grain quality, and contributes to knowledge of Austronesian cultures.
Highlights
IntroductionNoting that the world population is highly dependent on a cereal-based diet with chronic micronutrient deficiency, enhancement of crop and nutritional diversity by developing resource use-efficient crops and accelerating biofortification is important to food security [1]
Population growth and climate change both threaten to agricultural productivity
The 92 accessions designated with PI numbers that were collected by Wayne Fogg and deposited in the United States Department of Agriculture (USDA) in 1970s, were introduced back to Taiwan and deposited in the National Plant Genetic Resources Center (NPGRC), Taiwan Agriculture Research Institute (TARI) by the two co-authors, Qing-xiong Ba and Warren H
Summary
Noting that the world population is highly dependent on a cereal-based diet with chronic micronutrient deficiency, enhancement of crop and nutritional diversity by developing resource use-efficient crops and accelerating biofortification is important to food security [1]. Its lysine richness suggests the possible use of foxtail millet as a supplementary protein source to most cereals, and the majority of its crude fat is unsaturated, such as linoleic acid [1, 2]. With a short growing season, good productivity on barren soils and adaptation to extreme environments such as drought tolerance, foxtail millet is a preferred choice for improving food and nutritional security in the semi-arid tropics. Foxtail millet ranks second in total world production among millets, cultivated as staple food in semi-arid tropics of Asia such as China and India, and as fodder and hay in Europe, North America, Australia, and North Africa [3, 4]
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