Alfalfa, Medicago sativa, is a link connecting crop production and animal husbandry and plays a dominant role in the development of the livestock sector. The productivity of alfalfa is adversely affected by aphids’ feeding damage and their capacity to transmit viral plant pathogens. To increase alfalfa forage yield, it is imperative to control pest insects and use resistant varieties. The aim of this study was to identify the mechanism of M. sativa resistance to aphids by examining changes in the physiology, feeding behavior, and life history of the pests. The leaves of Gannong No. 5 (HA-3, aphid-resistant cultivar) had denser, longer trichome and thicker cortical parenchyma cell, and greater xylem thicknesses than those of Hunter River (Hu, aphid-susceptible cultivar). Nonprobing behaviors suggested that the spotted alfalfa aphid, Therioaphis trifolii, became more active in searching for suitable feeding sites on HA-3 than on Hu plants. Additionally, T. trifolii showed shorter durations for salivating into sieve elements and ingesting phloem sap on HA-3 plants. Life-table analysis showed that T. trifolii on HA-3 had longer developmental duration, higher mortality rate, and lower fecundity, net reproductive rate, intrinsic rate of increase, finite rate of increase and gross reproduction rate values than that on Hu plants. Moreover, relative fitness was significantly reduced in T. trifolii on HA-3 plants. The results of this study provided a basis for developing better control strategies for T. trifolii and studying the mechanisms of alfalfa resistance to aphids.

中文翻译：

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三叶草蚜虫（半翅目：蚜科）对 2 个苜蓿品种的取食行为和生活史参数

苜蓿（Medicago sativa）是连接农作物生产和畜牧业的纽带，在畜牧业发展中发挥着主导作用。苜蓿的生产力受到蚜虫的摄食损害及其传播病毒植物病原体的能力的不利影响。要提高苜蓿草料产量，必须防治病虫害，使用抗性品种。本研究的目的是通过检查害虫的生理、摄食行为和生活史的变化来确定苜蓿对蚜虫的抗性机制。甘农5号（HA-3，抗蚜品种）的叶片比亨特河（Hu，蚜敏感品种）的叶片更密、更长，皮层薄壁细胞更厚，木质部厚度更大。非探测行为表明，斑点苜蓿蚜 Therioaphis trifolii 在寻找 HA-3 上的合适取食位点方面比在 Hu 植物上更加活跃。此外，T. trifolii 在 HA-3 植物上分泌唾液和摄取韧皮部汁液的持续时间较短。生命表分析表明，HA-3上的三叶草比Hu植物上的发育持续时间更长，死亡率更高，而繁殖力、净繁殖率、内在增长率、有限增长率和总繁殖率值较低。此外，HA-3 植物上的三叶草的相对适合度显着降低。本研究结果为制定更好的三叶苜蓿防治策略和研究苜蓿抗蚜虫机制提供了基础。