Evaluation of forage grass resistance to Mahanarva fimbriolata (Stål)

ABSTRACT The aim of this study was to select forage grasses with potential resistance to Mahanarva fimbriolata by assessing effects on insect. No-choice assays were conducted with 12 genotypes and laboratory-reared insects. The following parameters were assessed: mortality and duration of the nymphal stage; adult weight and longevity; pre-oviposition period; number of eggs/female; viability and duration of the embryonic period. As main result it was verified that the mortality of nymphs reared on Panicum maximum cv. Paredão is almost complete and that this forage grass may be characterized as resistant to this insect by antibiosis. Further, the grasses can be divided into three groups following a cluster analysis: P. maximum cv. Aries, Setaria sphacelata cv. Kazungula, Brachiaria humidicola, A. gayanus and P. maximum cv. Aruana, which are insect-resistant grasses; Brachiaria decumbens cv. Basilisk, B. dictyoneura, B. brizantha cv. MG-4 and B. ruziziensis, which are moderately resistant grasses; and B. brizantha MG-5 and B. brizantha ecotype BB185, which are susceptible grasses.

摘要
本研究旨在通过评估供试昆虫的响应，筛选出对Mahanarva fimbriolata具有潜在抗性的饲用牧草。本研究采用12个基因型的饲用牧草与实验室饲养的供试昆虫，开展非选择性生测试验，测定指标包括：若虫死亡率、若虫期时长、成虫体重、成虫寿命、产卵前期时长、单雌产卵量、胚胎存活率以及胚胎期时长。
主要研究结果显示，取食大黍（Panicum maximum）品种‘Paredão’的若虫死亡率近乎100%，该饲用牧草可通过抗生性机制被认定为对该昆虫具有抗性。进一步通过聚类分析可将供试牧草划分为三类：第一类为抗虫牧草，包含大黍（Panicum maximum）品种‘Aries’、Setaria sphacelata品种‘Kazungula’、湿生臂形草（Brachiaria humidicola）、A. gayanus以及大黍（Panicum maximum）品种‘Aruana’；第二类为中抗牧草，包含俯仰臂形草（Brachiaria decumbens）品种‘Basilisk’、B. dictyoneura、B. brizantha品种‘MG-4’以及鲁齐兹臂形草（Brachiaria ruziziensis）；第三类为感虫牧草，包含B. brizantha品种‘MG-5’以及B. brizantha生态型BB185。