| Wheat landraces were defined as wheat complexes which could adapt to specific environment, maintain relative stability in genetics during long-term cultivation process. They are the product of artificial selection and natural selection. Wheat landraces in Southwest of China are valuable resources for wheat genetic improvement because of some valuable characters, such as big size in spikes and seeds, short growth period, pre-harvest sprouting resistance and so an. The study analyzed and evaluated the main agronomic traits and pre-harvest sprouting resistance of 191 wheat landraces from Southwest of China, additionally, using DArT chips which covering the whole genome of wheat, we did marker-trait associations and identified a few significant DArTs that associated with agronomic traits and pre-harvest sprouting. The results were described as follows:1. With the variance and correlation analysis, higher variation of the 15 agronomic traits was observed among all accessions. For example, wheat landraces were generally higher in plant height, later in heading time. The result of correlation analysis indicated that heading time and kernels per spike had extremely significant positive relationships, as for heading time and plant height had significant negative relationships, while heading time and flag leaf length, flag leaf width, grains per spike and other agronomic traits had extremely significant negative relationships; seed straight length and seed straight width, perimeter, surface area, volume had extremely significant positive relationships, while seed straight length and W/L ratio had extremely significant negative relationships.2. The principal component analysis of 15 agronomic traits indicated that there were 5 selected eigenvalues and the corresponding eigenvectors of cumulative contribution rate was 83.931%. The first principal component was weight factor, with which contribution rate at 43.027%; the second principal component was grain length factor, with which the contribution rate at 16.490%; the third principal component was spike number factor, with which contribution rate at 10.383%; the fourth principal component was flag leaf length factor, with which contribution rate at 8.544%; and the fifth principal component was flag leaf width factor, with which contribution rate at 6.487%. The results of cluster analysis showed that all materials were clustered into four groups at the level of 4.0 genetic distance value. Group â… belonged to the class with high plant height and multi-grain type, group â…¡ belonged to the class in mature early and big grain type; group â…¢ in the class of short plant height and small spike type; group â…£ was the class in mature late and small kernel. The result showed that there were no direct relationship between genetic divergence and geographical origins.3. By using 18938 DArT markers, we did genome-wide association study (GWAS) of 15 agronomic traits. The results showed that by using a general linear model (GLM), we identified 86 significant DArT makers which was significantly associated with 12 agronomic traits both in three environment; and a mixed linear model (MLM) revealed 106 significant markers associated with 15 agronomic traits. Both models detected 4 significant markers which associated with kernels per spike, 1000-grain weight and grain weight per panicle.4. Pre-harvest sprouting resistance of 191 wheat landraces were investigated through the seed germination experiment. The result showed as follows:analysis of variance revealed significant variation among accessions for pre-harvest sprouting resistance; the lowest and highest germination rate was at 0% and 100%, respectively. And average rate was 47.18%; the correlation coefficient of germination rate in 2013WJ, 2014WJ, and 2014CZ were significant at 0.01 level. According to the analysis of materials geographical origin, wheat landraces in Sichuan were with better resistance to pre-harvest sprouting, while wheat landraces from Tibet were most susceptible to pre-harvest sprouting.5. By using 18938 DArT markers, we did GWAS of pre-harvest sprouting resistance. The result showed that by using GLM, we identified 61,225,76 DArT makers in 2013WJ,2014WJ and 2014CZ, in which 23 markers were both detected in the three environments; and a MLM revealed 8,9,6 significant markers in 2013WJ,2014WJ and 2014CZ, respectively, which both distributed on the 3D chromosomes of wheat.6. Based on the analysis of the agronomic traits, we can select the right material for production or research depends on different needs. For example, AS662034 and AS661786 were extreme materials at kernel traits, the minimum and the maximum in seed size. Pre-harvest sprouting resistance identification showed that, there were 6 cultivars with stable pre-harvest sprouting resistance, here is the list of these cultivars:AS661571 planted in Bazhong, Sichuan, AS661583 from Changning, Sichuan, AS661617 from Shuangliu, Sichuan, AS661655 from Qianwei, Sichuan, AS661667 in Wuchuan, Guizhou and AS662043 in Bomi, Tibet. |
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