Agronomic traits and cluster analysis of winter wheat varieties (lines) in the Huanghuai and the middle/lower reaches of the Yangtze River wheat areas

Climate warming is having a great impact on wheat breeding and production in China and worldwide. To study the regulation mechanisms of the agronomic characteristics of wheat varieties (lines) adapting to climate change in different ecological wheat areas in China, this study selected 20 materials of wheat from the north and south of the Huanghuai winter wheat areas and the middle and lower reaches of the Yangtze River winter wheat area, including good varieties with currently large distributions, new approved varieties, and new breeding lines. The experiment was conducted in Shijiazhuang City of Hebei Province, which is located to the north of the Huanghuai winter wheat area. The drought and cold resistance, root-shoot ratio, and dry leaf weight ratio were investigated before the reviving stage. After harvest, the yield and ten agronomic characteristics, including plant height, spike length, internode length under the spike, tillers number, spikelets number, grains number per spike, 1000-grain weight, biomass per plant, grains weight per plant, and economic index were tested, after which correlation, clustering, and principal component analyses were carried out. The results showed that the drought and cold resistance of different wheat varieties (lines) at the seedling stage was in the order of the north of Huanghuai winter wheat area > the south of Huanghuai winter wheat area > the middle and lower reaches of the Yangtze River winter wheat area. There were extremely significant positive correlations between grains weight per plant and tillers number, grains number per spike, biomass per plant, and economic index in three ecological wheat areas. There were more agronomic characteristics with significant and extremely significant positive correlations in the south of the Huanghuai winter wheat area and the middle and lower reaches of the Yangtze River winter wheat area, indicating that the varieties from these two ecological wheat areas had great similarities. However, there were some differences in the positive and negative correlations among other agronomic traits in different ecology wheat areas. The 20 wheat varieties (lines) were divided into two ecotypes at a Euclidean distance of 20. Varieties (lines) from the middle and lower reaches of the Yangtze River winter wheat area and the south of the Huanghuai winter wheat area were in the type Ⅰ, and those from the north of the Huanghuai winter wheat area in the type Ⅱ. The type Ⅰ was further divided into three sub-classes at a Euclidean distance of 6, which were represented by 'Bainong 207' 'Jimai 22' and 'Xinong 979', respectively. The type Ⅱ was represented by 'Changhan 58'. There were four principal components, yield, spike length, plant height, and economic index, which contributed to over 76.39% of the performance variation of the ten agronomic traits. 'Jimai 22' and other varieties (lines) from the north of the Huanghuai winter wheat area accounted for 95% of the varieties (lines) whose comprehensive scores were ranked in the top 20 varieties (lines). These results provide important reference information for wheat breeding and adaptions to climate warming.