BIOTYPE-E GREENBUG REPRODUCTION AND DEVELOPMENT THROUGH 3 GENERATIONSON RESISTANT AND SUSCEPTIBLE WATER WHEAT GENOTYPES

Biotype E greenbugs, Schizaphis graminum (Rondani), reared through thr ee generations on a resistant winter wheat germplasm line, TXGBE273, t hat differed generically from the susceptible wheat cultivar 'TAM 105' at the Gb2 and Gb3 greenbug-resistance loci, showed a significant red uction in total number of nymphs produced per adult (23.3, 26.9, and 2 6.2 vs. 63.7, 61.7 and 55.8, respectively, for three generations), ave rage nymphs per adult per day (0.9, 0.9, and 1.0 vs. 2.1, 2.1 and 1.7, respectively, for three generations), total lifespan (29.9, 31.1 and 27 d vs. 33.2, 34 and 33 d, respectively, for three generations) and a dult lifespan (24.5, 25.5 and 21.7 d vs. 29.0, 29.7 and 28.9 d, respec tively, for three generations) compared to greenbugs reared exclusivel y on TAM 105. Nymphal period for these same greenbugs reared on TXGBE2 73 was significantly longer than those reared on TAM 105 (5.4, 5.6. an d 5.3 d vs. 4.2, 4.2 and 4.1 d, respectively, for three generations). The same significant differences were noted in estimates of the intrin sic rate of increase (0.192, 0.182, and 0.185 vs. 0.312, 0.305, and 0. 304. respectively, for three generations), and similar trends were not ed in mean generation time and net reproductive rare. The effects of t he resistance Factors on reproduction and lifespan remained constant a cross generations and were not found to carry over from one generation to the next. When greenbugs were reared for two generations on TXGBE2 73 and then returned to TAM 105 for the third generation, the aphids r ebounded to reproductive and lifespan parameters that were near those observed using only TAM 105 as the host, although still significantly lower in all categories other than average nymphs per adult per day (1 .8 and 1.7, respectively, for greenbugs from TXGBE273 back to TAM 105 and those reared exclusively on TAM 105).