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其对昆虫的影响，筛选出对蔗根扁蜡蝉（Mahanarva fimbriolata）具有潜在抗性的饲用牧草。本研究采用12个供试基因型与实验室饲养的试虫开展无选择取食试验（no-choice assays），测定的指标包括：若虫死亡率与若虫期时长、成虫体重与寿命、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，在大黍（Panicum maximum） cv. Paredão上饲养的若虫死亡率近乎完全，该饲用牧草可通过抗生性（antibiosis）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，涵盖大黍（Panicum maximum） cv. Aries、束状尾稃草（Setaria sphacelata） cv. Kazungula、湿生臂形草（Brachiaria humidicola）、盖氏鸭嘴草（Andropogon gayanus）与大黍（Panicum maximum） cv. Aruana；第二类为中度抗虫牧草，包括俯仰臂形草（Brachiaria decumbens） cv. Basilisk、网脉臂形草（Brachiaria dictyoneura）、布氏臂形草（Brachiaria brizantha） cv. MG-4以及鲁济兹臂形草（Brachiaria ruziziensis）；第三类为感虫牧草，涵盖布氏臂形草MG-5与布氏臂形草生态型BB185。