牛角花齿蓟马为害对苗期紫花苜蓿根、冠生长的影响

Effects of Odontothrips loti on root and shoot growth of alfalfa seedlings

摘要:

【目的】探索苗期紫花苜蓿的根、冠生长对牛角花齿蓟马（Odontothrips loti）为害的响应及其与苜蓿耐害性的关系。【方法】以甘农 9 号紫花苜蓿（Medicago sativa cv. Gannong No. 9）为试验材料，在不同牛角花齿蓟马虫口压力（0、1、3、5 头/株）下，评价紫花苜蓿的抗性表现，测定紫花苜蓿的根茎叶生长特性及生物量。【结果】随着虫口压力的增加，紫花苜蓿的受害指数持续升高，株高和茎粗持续下降。 受害初期，紫花苜蓿叶面积、侧枝数、侧枝长、主根直径、侧根数、侧根长和根茎叶生物量增大，根颈直径变细。受害中期，随虫口压力的增大，紫花苜蓿叶面积持续下降，侧枝长、主根直径和根颈直径下降；侧枝数和侧根长增大，侧根数和根茎叶生物量 1、3 头/株压力下增加，在 3 头/株下最大。但在高虫口压力 （5 头/株）下降。受害后期，随虫口压力的增大，苜蓿叶面积、侧枝长、主根直径、根颈直径和根茎叶生物量持续下降；侧根长随虫口压力的增大持续上升，侧枝数和侧根数在低虫口压力增大，均在 3 头/株时最高，但在高虫口压力（5 头/株）下降。【结论】牛角花齿蓟马的适度危害（低于 3 头/株）可激发苗期苜蓿的侧枝和侧根生长，扩大了植株冠层的光合面积，提高了根系对土壤水分和矿物质营养的吸收能力， 进而使紫花苜蓿产生超补偿生长，增强了紫花苜蓿对蓟马的耐害性。而虫口压力过大（5 头/株）则抑制了紫花苜蓿侧枝和侧根的生长，最终表现为不足补偿，其耐害性减弱。

Abstract:

In order to explore the response of the root and shoot growth of alfalfa seedling to Odontothrips loti thrip damage and the relationship with alfalfa tolerance. In this experiment，Medicago sativa cv. Gannong No. 9 al- falfa was used as the experimental material to evaluate the resistance performance of alfalfa by mearing the root，stem and leaf growth and biomass of alfalfa under different O. loti population pressure （0，1，3 and 5 heads thrips/plant）. The results showed that the damage indexes of alfalfa increased continuously with the increase of O. loti population ， while the plant height and stem diameter decreased continuously. In the early stage of damage，the alfalfa leaf area，lat- eral branch numbers，lateral branch length，taproot diameter，lateral root numbers，lateral root length and root stem leaf biomass increased，but the root collar diameter became thinner. During the middle stage of damage，the leaf area of alfalfa decreased continuously with the increase of thrips pressure，whereas the lateral branch length，the taproot di- ameter and root collar diameter decreased. The numbers of lateral branch and the length of lateral roots increased， while the numbers of lateral root and the biomass of root，stem and leaf increased at the lower thrips population （1，3 heads thrips/plant ） and decreased at the higher thrips population （5 heads/plant. In the late stage of damage，the leaf area，lateral branch length，taproot diameter，root collar diameter and root，stem and leaf biomass of alfalfa decreased and the lateral root length increased continuously with the increase of thrip population. The numbers of lateral branch and lateral root increased at the lower population and decreased at the higher population. The moderate damage of O. loti（less than 3 head/plant） could stimulate the growth of branch and lateral root of alfalfa at seedling stage，which enlarged the photosynthetic area of plant crown，and improved the absorption capacity of root to soil water and min- eral nutrition. The regenerate growth capacity of alfalfa was improved，and produced over-compensatory growth，thus enhanced the tolerance of alfalfa to thrips. However，the growth of branch and lateral root of alfalfa were inhibited by the excessive pressure of thrips （5 heads/plant），so that the growth performance of alfalfa was under-compensation fi- nally，and the tolerance of alfalfa was weakened.