摘要:为了明确施磷后紫花苜蓿根、茎、叶中光合产物分配与苜蓿抗蓟马能力的关系，本试验以紫花苜感虫品种‘甘农3号’和抗虫品种‘甘农9号’为材料，以北方苜蓿蓟马类优势害虫牛角花齿蓟马（Odontothrips loti）为研究对象，设0 mg（P2O5）·kg-1（土）、27 mg（P2O5）·kg-1（土）、54 mg（P2O5）·kg-1（土）、81 mg（P2O5）·kg-1（土）和108 mg（P2O5）·kg-1（土）5个磷水平，分别记为P0、P1、P2、P3和P4，在苜蓿6叶期，按3头·株-1接入牛角花齿蓟马，分别于苜蓿持续受害7 d、14 d和21 d时，评价苜蓿的受害指数，测量单株叶、茎、根生物量和根、茎、叶中的可溶性糖和淀粉含量。结果表明：随着施磷水平的升高，‘甘农3号’和‘甘农9号’苜蓿的受害指数降低，总体以P3水平下最低；受害7 d时，两个苜蓿品种受害指数均下降但不显著；受害14 d和21 d时受害指数下降显著（P < 0.05）。施磷后苜蓿根、茎和叶生物量均显著增加，在蓟马为害前期（7 d）和中期（14 d）苜蓿受害较轻时，生物量向叶中分配较多；在受到持续较重的为害后（21 d），苜蓿的生物量更多向根系分配，相应分配到叶部的生物量有所下降，茎秆中的生物量分配比例变化不显著。相对于‘甘农3号’，各施磷水平下‘甘农9号’分配到叶中的生物量更多。施磷后苜蓿根、茎和叶中可溶性糖和淀粉含量显著增加，随着受害时间的持续，苜蓿根、茎和叶中的淀粉含量总体下降，而可溶性糖含量持续增加；在受害14 d和21 d时，‘甘农9号’的叶和根中的可溶性糖及淀粉含量明显高于‘甘农3号’。总之，施磷可有效增强苜蓿对蓟马的耐害性，在虫害压力适中时，施磷促进了苜蓿地上部分的补偿生长，虫害压力较大时，施磷保证根系的生长以维持其生存。随着受害时间的持续，苜蓿存贮型碳水化合物淀粉的含量趋向减少，根、茎和叶中的可溶性糖含量升高，使较多的资源用于苜蓿光合器官和贮藏器官的构建。P3水平[81 mg（P2O5）·kg-1（土）]为本试验中苜蓿最佳施磷水平。
关键词:施磷量/
牛角花齿蓟马/
紫花苜蓿/
光合产物/
分配/
抗虫性
Abstract:The aim of this research was to clarify the distribution of carbohydrates in the roots, stems, and leaves of alfalfa with different phosphorus application rates, and the alfalfa's resistance to thrips. Two alfalfa varieties, 'Gannong No. 3' and 'Gannong No. 9, ' were used in this study. Odontothrips loti, which was the dominant pest of thrips in the alfalfa planting area of northern China, was selected as the research subject. Five soil phosphorus levels [0 (P1), 27(P2), 54(P3), 81(P4), and 108 mg(P2O5)·kg-1soil (P5), were set. And alfalfa was infested with O. loti of 3 head·plant-1 at the 6 leaf stage. The damage index was evaluated; the biomass of the leaves, stems and roots were measured; and the soluble sugar and starch contents of the leaves, stems, and roots were determined after the alfalfa was damaged by O. loti for 7, 14, and 21 days. The result showed that the damage index of 'Gannong No. 3' and 'Gannong No. 9' decreased gradually with increased phosphorus level, the lowest being at P3 level. The damage index of both alfalfa varieties decreased significantly after 14 and 21 days. The leaf, stem and root biomass of both alfalfa varieties increased significantly with increased phosphorus level. More biomass was distributed to the leaves in the early and middle stages (7 and 14 days), while it was distributed to the roots in the period of serious injury (21 days). However, the biomass allocated to stems was not significant. In 'Gannong No. 9', the biomass allocated to the leaves was more than that in 'Gannong No. 3' at the same phosphorus level. The soluble sugar and starch contents of the leaves, stems, and roots increased significantly with phosphorus level increasing. The soluble sugar content of the roots, stems and leaves increased, while the starch content decreased as the period of damage increased. The soluble sugar and starch contents of the leaves and roots of 'Gannong No. 9' were significantly higher than those of 'Gannong No. 3', which was damaged by thrips for 14 and 21 days. Phosphorus application enhanced the tolerance of alfalfa to thrips, with greater effect on 'Gannong No. 3'. Phosphorus application promoted the compensatory growth of the aboveground part at the moderate pest pressure and helped maintain root growth for the survival of alfalfa under severe pest pressure. Correspondingly, with the increase in damage time, the starch content of the root, stem, and leaves tended to decrease, and the soluble sugar content increased, showing that more resources were used to develop the photosynthetic and storage organs. P3 [81 mg(P2O5)·kg-1 soil] was the best fertilization level for enhancing alfalfa's resistance to thrips in this research.
Key words:Phosphorus application rate/
Odontothrips loti/
Alfalfa/
Photosynthetic products/
Distribution/
Insect resistance
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