Relationship between Polymorphism of <I>Wx</I> Gene and Amylose Content in Hulless Barley

Abstract

Hulless barley ( Hordeum vulgare L. var. nudum Hook. f.) is a typical crop in Tibetan Plateau in China. Starch, including amylopectin and amylose, is the main storage component in hulless barley, of which amylose is in low content or even absent in the endosperm of waxy barley. The Waxy gene ( Wx ) located on the short arm of chromosome 7H is a key gene responsible for amylose synthesis, and also acts as a favorable gene in breeding of hulless barley. However, it is difficult to select hulless barley germplasm with Wx due to lack of effective molecular markers. This study aimed to find out molecular markers applicable in the identification of Wx gene. A total of 150 accessions of hulless barley were primarily tested by staining endosperm with I 2 -KI, and four accessions (IG107028, Puebla, Huzhushuangcaoren, and APM-HC1905) were found as waxy genotypes. The amylose contents (AC) of the 150 accessions measured using dual-wave length spectrophotometry method varied from 12.4% to 38.5% with an average of 26.0%. The amylose contents of the four waxy genotypes namely IG107028, Brachvtic, Kunlun 2, and Huzhushuangcaoren，were 12.4–18.6% with an average of 16.7%. No genotype was found without amylose. We selected 51 accessions with obvious difference in AC to validate the polymorphism of four pairs of SSR markers. Primers P1 and P3 showed no polymorphism among the 51 accessions, and primer P4 exhibited four types of amplified product, and the fragment size positively correlated with amylose content. The P4 primer was designed according to the sequence of Wx gene on chromosome 7H of barley. Primer P4 can be used as an effective marker in the selection of waxy hulless barley cultivars.