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对条纹墨胸沫蝉（Mahanarva fimbriolata）的影响，筛选出对其具有潜在抗性的饲草品种。本研究以12个饲草基因型与实验室饲养的该昆虫开展非选择性试验，测定指标包括：若虫死亡率与若虫期时长、成虫体重与成虫寿命、产卵前期、单雌产卵量、胚胎存活率与胚胎期时长。主要研究结果证实，取食大黍（Panicum maximum）品种Paredão的若虫死亡率近乎100%，该饲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饲草划分为三类：第一类为抗虫饲草，包括大黍品种Aries、斯帕切拉狗尾草（Setaria sphacelata）品种Kazungula、湿生臂形草（Brachiaria humidicola）、盖氏须芒草（A. gayanus）以及大黍品种Aruana；第二类为中抗饲草，包括俯仰臂形草（Brachiaria decumbens）品种Basilisk、网脉臂形草（Brachiaria dictyoneura）、栅锈臂形草（Brachiaria brizantha）品种MG-4以及鲁济兹臂形草（Brachiaria ruziziensis）；第三类为感虫饲草，包括栅锈臂形草MG-5以及栅锈臂形草生态型BB185。