The Analysis Of Lipoxygenase In Bread Wheat Cultivars From The Yellow And Huai Wheat Area Of China

Wheat flour color and luster are the important quality of wheat, the color improvement has become one of the significant goals for wheat quality breeding. The lipoxgenase in grain will oxidate the carotenoids in wheat flour to attain to biological bleach, so it is the important factor influencing the flour color. However, high level of LOX activity will cause the deterioration of wheat quality and the loss of nutritional value, so the study of molecular genetic mechanism of LOX gene is of great significance to improve the wheat quality in our country.In the paper a total of 306 wheat cultivars or advanced lines from the Yellow and Huai wheat area of China were selected to identify the LOX(Lipoxygenase) activity and allelic variations of LOX genes, and Spectrophotometer and Microplate were used to measure the LOX activity. The molecular marker Xwmc312 on chromosome 1AL and the functional markers LOX16 and LOX18 on chromosome 4BS were employed to identify the polymorphism of the LOX genes in the tested materials by combinations of PCR(Polymerase Chain Reaction) amplification and agarose and polyacrylamide electrophoresis gels. The major results were showed as followed:1. The phenotyping results showed that the averaged of LOX activity was 65.73 AU·min-1·g-1 and standard deviation(SD) was 13.54 in the wheat cultivars from the Yellow and Huai valley, ranging from 27.09 to 99.55 AU·min-1·g-1 with a variation coefficient of 20.6%. Among the wheat cultivars tested LOX activity had the 7 wheat cultivars were less than 40 AU·min-1·g-1 and 8 exceeded 90 AU·min-1·g-1. These cultivars could provide an important germplasms for improvement of LOX activity of currently popular wheat in wheat breeding program.2. Based on the analysis of interaction relationship between genotype and environment, the difference of LOX activity among genotypes, environments and genotype by environment interaction effect reached to extremely significant level(P<0.01), and it’s heritability was 65.49%.3. Genotyping results indicated that three alleles, Xwmc312227, Xwmc312235 and Xwmc312247, were found at the QLpx.caas-1AL locus in these wheat varieties, accounting for 30.4%, 19.0% and 50.6%, respectively. At Ta LOX-B1 locus, two alleles, Ta LOX-B1 a and Ta LOX-B1 b, were identified by the functional markers LOX16 and LOX18 with a rale of 28.8% and 71.3%, respectively. Six allele combinations of LOX genes, i.e., Ta LOX-B1a/Xwmc312227, Ta LOX-B1a/Xwmc312235, Ta LOX-B1a/Xwmc312247, Ta LOX-B1b/Xwmc312227, Ta LOX-B1b/Xwmc312235 and Ta LOX-B1b/Xwmc312247 were found in the bread wheat cultivars surveyed with 7.2%, 9.5%, 12.1%, 23.2%, 9.5% and 38.6% respectively.4. Analysis of association of LOX alleles and LOX activity indicated that the average LOX activity of wheat cultivars with Xwmc312235 was significantly higher than those with Xwmc312227 and Xwmc312247, and the average LOX activity of cultivars with Ta LOX-B1 a was significantly higher than those with Ta LOX-B1b(P < 0.05). Moreover, analysis of association of LOX allele combination and LOX activity showed that the LOX activity(76.803 AU·min-1·g-1) of the cultivars with Ta LOX-B1a/Xwmc312235 was significantly higher than those with other five LOX allele combinations, whereas the LOX activity(62.45 AU·min-1·g-1) cultivars with Ta LOX-B1b/Xwmc312227 genotype was significantly lower than those of other five combinations.5. Most of the wheat cultivars from the Yellow and Huai valley had the middle LOX activity, while the wheat cultivars with extremely low(less than 40 AU·min-1·g-1) or high(more than 90 AU·min-1·g-1) LOX activities were very scarce. Amongst 6 different combinations of LOX genes, wheat cultivars with Ta LOX-B1a/Xwmc312235 possessed relatively higher LOX activity and wheat cultivars with Ta LOX-B1b/Xwmc312227 possessed relatively lower LOX activity(P < 0.05). This study could also provide the important information for wheat quality improvement in China.6. Four wheat varieties with low LOX activity were selected based on the LOX activity and the allele combination from the 306 wheat varieties(lines) of three varieties were from henan province, and the chixiaomai from Japan, which had been widely and effectively used in the breeding of dwarf in the world. We also screened out 5 germplasm resources with high LOX activity, four from henan province and one from shanxi province. In addition, yumai 2 had fine comprehensive properties, good stability and high combining ability, especially the high heritability of quality, which had been used by many scientific research units as the backbone parent, and a large number of excellent new varieties were breed from it.