不同产量水平甘薯品种光合产物分配差异及其原因

选取我国北方薯区主栽的食用型甘薯品种龙薯9号、红香蕉、泰中6号、苏薯8号、遗字138和北京553,于2011—2012年2个生长季在山东农业大学农学试验站进行大田试验,研究不同产量水平甘薯品种光合产物的分配差异及其原因。在甘薯主要生长时期测定茎蔓各部位蔗糖含量和基部茎粗、在块根膨大过程中对功能叶进行13C标记,探索不同品种13C同化物分配特点,同时研究上述项目与收获指数和块根产量的关系。结果表明,高产品种龙薯9号、红香蕉、泰中6号和苏薯8号产块根均在60 t hm–2左右,而中、低产品种遗字138和北京553产块根在50 t hm–2以下。高产品种的收获指数显著高于中、低产品种。在块根膨大前期高产品种的块根成为光合产物的分配中心,而中、低产品种的块根则在块根膨大后期成为分配中心;在块根膨大前、中期,高产品种13C同化物在块根中的分配比例显著高于中、低产品种,即高产品种光合产物由功能叶向块根的转运能力强于中、低产品种。供试品种茎蔓基部的蔗糖含量均高于顶部,且中、低产品种的蔗糖浓度差大于高产品种;随着甘薯生长发育,中、低产品种茎蔓基部增粗速率高于高产品种。相关分析表明,块根产量与收获指数呈极显著正相关(r=0.98**,2011;r=0.93**,2012);块根13C分配率与块根产量和收获指数均呈显著正相关(0.87*和0.91**,2011;0.92**和0.99**,2012);生长中后期,基部茎粗与块根产量和收获指数均呈显著负相关(–0.78*和–0.83*;–0.88**和–0.95**)。块根成为光合产物分配中心的时间早、光合产物由功能叶向块根的转运能力强是高产品种收获指数显著提高的主要原因,而中、低产品种光合产物由叶片向块根转运能力差的主要原因是块根中光合产物卸载不畅。

Difference and Related Reason for Assimilate Distribution of Sweetpotato Varieties with Different Tuber Root Yields

A field experiment was conducted at agricultural experiment station of Shandong Agricultural University, Tai’an, Shandong Province in two growth seasons of 2011 and 2012. Six typical varieties of edible sweetpotato in North China were used, including Longshu 9, Hongxiangjiao, Taizhong 6, Sushu 8, Yizi 138, and Beijing 553, to study the difference and reason for assimilate distribution among varieties with different yield levels. The distribution characteristics of assimilate was studied by ¹³C labeling during storage roots development; sucrose content of different stem parts and stem base diameter were measured as well. And the relationship between the above traits and harvest index, tuber root yield was also analyzed. The results showed that the root tuber yield of high-yielding varieties (Longshu 9, Hongxiangjiao, Taizhong 6, and Sushu 8) was about 60 t hm^–2, whereas that of intermediate and low-yielding varieties (Yizi 138 and Beijing 553) was less than 50 t hm^–2. And the harvest index of high-yielding varieties was significantly higher than that of intermediate and low-yielding varieties. The root tuber of high-yielding varieties became assimilate distribution center at early bulking stage, while for intermediate and low-yielding varieties that was at late bulking stage; and high-yielding varieties also had significantly higher ¹³C distribution rate than that of intermediate and low-yielding varieties, indicating that high-yielding varieties had relatively higher ability to transport assimilate from functional leaves to root tubers. Sucrose content of stem base was higher than that of stem top, and the sucrose concentration gradient of intermediate and low-yielding varieties was higher than that of high-yielding varieties. Low-yielding varieties’ stem base thickened faster than high-yielding varieties in the development of sweetpotato. The correlation analysis showed that root tuber yield had significantly positive correlation with harvest index (r = 0.98^**, 2011; r = 0.93^**, 2012). Root tuber yield and harvest index had significantly positive correlation with ¹³C distribution rate of root tuber (0.87^* and 0.91^**, 2011; 0.92^** and 0.99^**, 2012); they also had significantly negative correlation with stem base diameter during middle and late growth stages (–0.78^* and –0.83^*; –0.88^** and –0.95^**). Therefore, high-yielding varieties got higher harvest index mainly due to less time taken by their root tuber to become assimilate distribution center and stronger ability of assimilate transportation from functional leaves to root tubers; and low-yielding varieties got lower abilities of assimilate transportation mainly because assimilate unloading in root tubers was not smoothly.