An improved methodology for massive screening of Brachiaria spp. genotypesfor resistance to Aeneolamia varia (Homoptera : Cercopidae)

Several species and genera of spittlelbugs (Homoptera: Cercopidae) are econ omic pests of grasses in tropical America. They have the potential to cause serious losses on millions of hectares of improved pastures based on culti vars of several species of Brachiaria. Most of the available commercial cul tivars of Brachiaria are susceptible to spittlebug. Resistance has been ide ntified in several germplasm accessions and in one of the commercial cultiv ars, B. brizantha (A. Rich.) Stapf 'Marandu'. Brachiaria breeding projects require reliable techniques to screen for host plant resistance in large, s egregating populations. A series of experiments was conducted to improve ev aluation methodology. A smaller plant growth unit, supporting a single-stem , vegetative propagule, was developed and rested. Infestation levels for bo th adults (6 per plant) and for nymphs (10 per plant) were established. The refinements in screening methodology increase both reliability and capacit y of the screen. Infestation of smaller plant propagules saves time, space, and physical resources. It also allows clear expression of insect damage s ymptoms and hence permits discrimination between tolerance and antibiosis i n host plant reaction. Selection can be based on both resistance mechanisms . We outline a 2-yr Brachiaria breeding cycle which incorporates the new sp ittlebug resistance screening methodology.