Researches On Lodging-resistance Related Traits And Effects Of Vrn-D1b Allele On Agronomic Traits In Common Wheat

Yield and yield stability are complex quantitative traits and determined not only by yield components, but also by the lodging and vernalization genes related to plant growth and development in wheat. It is well known that lodging resistance has been improved efficiently by utilization of the semi-dwarf cultivars in wheat. However, excessive reduction in plant height will lead to the decrease of yield. Therefore, it is important to determine other lodging-associated traits, in addition to plant height, for improving lodging resistance in wheat breeding program. Vrn-D1 b was recently found in the wheat cultivars mostly distributed in Yellow and Huai River Valley Winter Wheat Zone in China. This allele has been proven to be associated with the facultative growth habit and has a great effect on growth and development in wheat, however the knowledge of its effect on agronomic trait is poor. Therefore, our researches were conducted in those two aspects mentioned above.In the present study, two groups of wheat cultivars and breeder’s lines with different lodging-resistant levels were used to evaluate the lodging-associated traits. One group consisted of the lodging resistant cultivars and breeder’s lines, including Shi 4185, Lunxuan 103, Lunxuan 163, Lunxuan 126, Aikang 58, Xiaoyan 101 and Zhoumai 18, and another group composed of lodging-susceptible cultivars and breeder’s lines, including Lunxuan 49, Lunxuan 136, Zhongmai 875, Lunxuan 87 and Lunxuan 199. Thirteen lodging-assoicated traits were evaluated in this study. The results showed that the group of lodging-resistant wheat entries had shorter plant height, shorter and thicker basal 1-2 internodes, thicker second internode wall, greater number of large and small vascular bundles, thicker parenchyma and sclerenchyma tissues, and stronger stem breaking strength. The significant differences（P ≤ 0.05） were detected between the two groups in plant height, length of the second internode, number of small vascular bundle, width of sclerenchyma tissue and stem breaking strength. It was noticed that different lodging-resistant entries had different lodging-resistant characteristics. The correlation and principal component analyses showed that plant height, length of second internode and stem breaking strength were the key characters in determining the lodging difference between the two groups of wheat entries, indicating that these three traits could be used as main criteria in selection for lodging resistance in wheat breeding program.The population of 100 F_3:8 derived lines and 196 RILs, was developed from Shi 4185 × Shijiazhuang 8 which have the same allelic variation at all known Vrn-1 loci except Vrn-D1, together with the two parents were evaluated in two environments using the lattice design with two replications. The results showed that in F_3:8 derived lines the Vrn-D1b-carrying lines had significantly higher grain yield（0.32 t ha-1, P ≤ 0.01）, more kernels per spike（1.2, P ≤ 0.01）, greater kernel weight（0.8 g, P ≤ 0.05）, higher seedling height（2.5 cm, P ≤ 0.01） and plant height（2.0 cm, P ≤ 0.01）, fewer sterile spikelet number per spike（0.3, P ≤ 0.01）, earlier in both heading date（1.0 d, P ≤ 0.01） and anthesis date（1.0 d, P ≤ 0.01）, compared to the vrn-D1-carrying lines. Compared to the vrn-D1 lines, the Vrn-D1 b lines had significantly higher grain yield in both parents and RILs, as well. In F_3:8 derived lines grain yield was positively correlated with seedling height（r = 0.47, P ≤ 0.01）, plant height（r = 0.37, P ≤ 0.01） and kernel number per spike（r = 0.51, P ≤ 0.01）, but negatively correlated with heading date（r =-0.50, P ≤ 0.01） and anthesis date（r =-0.55, P ≤ 0.01）. The similar results were found in RILs. Path analysis and clustering analysis based on PCA（principle component analysis） showed that the yield advantage of Vrn-D1 b lines over vrn-D1 lines was attributed primarily to the increased kernel number per spike. The findings of this study indicated that the presence of Vrn-D1 b allele has a positive role in improving grain yield in Yellow and Huai River Valley Winter Wheat Region.