Article pubs.acs.org/JAFC
Development of Barley (Hordeum vulgare L.) Lines with Altered Starch Granule Size Distribution Sarita Jaiswal, Monica Båga, Geetika Ahuja, Brian G. Rossnagel, and Ravindra N. Chibbar* Department of Plant Sciences, College of Agriculture and Bioresources, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan S7N5A8, Canada S Supporting Information *
ABSTRACT: Microscope analysis of starches prepared from 139 barley genotypes identified a Japanese genotype, Kinai Kyoshinkai-2 (KK-2), with altered starch granule size distribution. Compared to normal barley starch, KK-2 produced consistently higher volumes of starch granules with 5−15 μm diameter and reduced volumes of starch granules with >15 μm diameter when grown in different environments. A cross between KK-2 and normal starch cultivar CDC Kendall was made and led to the production of 154 F5 lines with alterations to the normal 7:3:1 distribution for A-:B-:C-type starch granule volumes. Three F5 lines showed unimodal starch granule size distribution due to apparent lack of very small (15 μm diameter) A-type starch granules as compared to normal starch and showed on average a 10:4:1 distribution for A-:B-:C-type starch granule volumes. The unusual starch phenotypes displayed by the F5 lines confirm starch granule size distribution in barley can be genetically altered. KEYWORDS: amylose, barley, image analysis, laser diffraction analysis, starch granule size distribution
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INTRODUCTION Starch is the major storage carbohydrate in cereal grains and is made up of two distinct polysaccharides, amylose and amylopectin. The proportion between amylose and amylopectin in normal barley starch is 1:3, but a few barley genotypes produce starches with different ratios.1,2 Amylose is essentially a linear polymer of α-(1→4) linked glucose residues and is sparsely branched due to few (one in 1000 glucose residues) α-(1→6) linkages.3 Amylopectin is a heavily branched molecule with α-(1→6) branch points at every 24−30 glucose residues along the α-(1→4) linked glucan backbone. The two glucan polymers are stored as discrete water insoluble granules, which also contain trace amounts of proteins, lipids, and minerals. Botanical origin, genetics, and environment influence the size and shape of starch granules, their properties, and end use. 4 Wheat, barley, rye, and triticale starches are unique as they have two distinct types of starch granules based on size and shape.5,6 The large A-type starch granules are lenticular with a diameter >15 μm, whereas the small B-type starch granules are round and have a diameter
