RELATIVE FITNESS OF GREENBUG (HOMOPTERA, APHIDIDAE) BIOTYPE-E AND BIOTYPE-I ON SORGHUM, WHEAT, RYE, AND BARLEY

Citation
R. Bowling et al., RELATIVE FITNESS OF GREENBUG (HOMOPTERA, APHIDIDAE) BIOTYPE-E AND BIOTYPE-I ON SORGHUM, WHEAT, RYE, AND BARLEY, Journal of economic entomology, 91(5), 1998, pp. 1219-1223
Citations number
28
Categorie Soggetti
Entomology,Agriculture
ISSN journal
00220493
Volume
91
Issue
5
Year of publication
1998
Pages
1219 - 1223
Database
ISI
SICI code
0022-0493(1998)91:5<1219:RFOG(A>2.0.ZU;2-K
Abstract
Greenbugs, Schizaphis graminum (Rondani),present a well-documented exa mple of the ability of insects to overcome designed host plant resista nce. Four greenbug biotypes have been identified on wheat, Triticum ae stivum L., and 3 on sorghum, Sorghum bicolor (L.) Moench, since greenb ugs were identified as pests of small grains. Biotype E has been the p redominant biotype since the mid-1980s. Greenbug biotype I is the most recent greenbug biotype identified in field plantings of small grains and may be replacing biotype E. Replacement of biotype E greenbug by biotype I will depend on the fitness of biotype I on biotype E-resista nt cultivars. We attempted to predict this event by assessing relative fitness of the 2 biotypes, defined by life history characteristics on sorghum, wheat, rye, Secale cereale L., and barley, Hordeum vulgare L . We used several sorghum cultivars or lines with differ ent reported levels of resistance to greenbug biotypes E and I, and 1 cultivar or l ine each of wheat, barley, and rye with reported resistance to biotype E. Biotype E development time, intrinsic rate of increase (r(m)), and to a lesser extent number of offspring produced were adversely affect ed by E-resistant and I-resistant sorghum cultivars or lines, whereas biotype I was only adversely affected by I-resistant cultivars or line s. Even on I-resistant cultivars or lines, biotype I outperformed biot ype E. Wheat line CI 1795 and barley cultivar 'Post', previously ident ified as resistant to greenbug biotype E, also showed resistance to gr eenbug biotype I. No differences occurred in the reproductive characte ristics of greenbugs between E-resistant and E-susceptible rye cultiva rs, Given these differences in fitness on both E- and I-resistant sorg hum and the importance of sorghum to greenbug population dynamics in t he central and northern plains (compared to wheat, barley, and rye), i t is likely that as increasing acreage is planted to these sorghum cul tivars biotype I will replace biotype E.