Li Hongsheng, Yang Zhonghui, Li Shaoxiang, Elfanah Ahmed M S, Abdelkhalik Sedhom, Tang Xiong, Yin Jian, Ding Mingliang, Liu Kun, Yang Mujun, Wang Xiue
State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Agriculture, Collaborative Innovation Center for Modern Crop Production (CIC-MCP), Nanjing Agricultural University, Nanjing 210095, China.
Food Crops Research Institute, Yunnan Academy of Agricultural Sciences, Kunming 650205, China.
Plants (Basel). 2024 Aug 15;13(16):2267. doi: 10.3390/plants13162267.
Wheat hybrids have been widely demonstrated to have remarkable heterosis or hybrid vigor in increasing yield potential and stability since the 1960s. Two-line hybrid wheat can achieve higher yields than local varieties, especially in marginal environments. However, the commercial application of hybrid wheat is hindered by higher seed costs, primarily due to lower yields in hybrid seed production. Stigma exsertion has been verified as a decisive factor in increasing rice's hybrid seed yield, but more investigation is needed in hybrid wheat breeding and production. In this study, four thermo-photo-sensitive genic male sterile lines, including K41S, K64S, K66S, and K68S, with different stigma exsertion rates (SERs) were used to compare the differences in floral architecture relative to stigma exsertion over two growing seasons. The results revealed that the K41S and K64S exhibited a relatively higher SER at 21.87% and 22.81%, respectively. No exserted stigma was observed in K66S, and K68S had an SER of only 0.82%. This study found that the stigma length, glume width and the length-width ratio of the glume were significantly correlated with the SER, with correlation coefficients of 0.46, -0.46 and 0.60, respectively. Other stigma features such as the branch angle, stretch width and hairbrush length, as well as the glume length, also had a weakly positive correlation with SER (r = 0.09-0.27). For K41S and K64S, the SER was significantly affected by the differences in the stigma branch angle and stigma stretch width among florets. A cross-pollination survey showed that the out-crossing ability of florets with an exserted stigma was about three times as high as that of florets with a non-exserted stigma. As a result, the stigma-exserted florets that accounted for 21.87% and 22.81% of the total florets in K41S and K64S produced 46.80% and 48.53% of the total cross-pollinated seeds in both sterile lines. These findings suggest that a longer stigma combined with a slender glume appears to be the essential floral feature of stigma exsertion in sterile wheat lines. It is expected that breeding and utilizing sterile lines with a higher SER would be a promising solution to cost-effective hybrid wheat seed production.
自20世纪60年代以来，小麦杂交种在提高产量潜力和稳定性方面已被广泛证明具有显著的杂种优势或杂交活力。两系杂交小麦比当地品种产量更高，尤其是在边际环境中。然而，杂交小麦的商业应用受到较高种子成本的阻碍，这主要是由于杂交种子生产中的产量较低。柱头外露已被证实是提高水稻杂交种子产量的决定性因素，但在杂交小麦育种和生产中还需要更多的研究。在本研究中，使用了四个温光敏核不育系，包括K41S、K64S、K66S和K68S，它们具有不同的柱头外露率（SERs），以比较两个生长季节中相对于柱头外露的花部结构差异。结果显示，K41S和K64S的SER相对较高，分别为21.87%和22.81%。在K66S中未观察到外露柱头，K68S的SER仅为0.82%。本研究发现，柱头长度、颖壳宽度和颖壳长宽比与SER显著相关，相关系数分别为0.46、-0.46和0.60。其他柱头特征，如分枝角度、伸展宽度和毛刷长度，以及颖壳长度，与SER也有弱正相关（r = 0.09 - 0.27）。对于K41S和K64S，SER受小花间柱头分枝角度和柱头伸展宽度差异的显著影响。异花授粉调查表明，外露柱头小花的异交能力约为非外露柱头小花的三倍。因此，在K41S和K64S中，占小花总数21.87%和22.81%的外露柱头小花产生了两个不育系中异花授粉种子总数的46.80%和48.53%。这些发现表明，较长的柱头与细长的颖壳相结合似乎是不育小麦系柱头外露的基本花部特征。预计培育和利用具有较高SER的不育系将是实现经济高效杂交小麦种子生产的一个有前景的解决方案。
