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Title: OVER-SUMMERING AND BIOTYPIC DIVERSITY OF SCHIZAPHIS GRAMINUM (HOMOPTERA: APHIDIDAE) POPULATIONS ON NON-CULTIVATED GRASS HOSTS

Author
item ANSTEAD, JAMES - OKLAHOMA STATE UNIVERSITY
item Burd, John
item Shufran, Kevin

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2002
Publication Date: 2/15/2003
Citation: ANSTEAD, J., BURD, J.D., SHUFRAN, K.A. OVER-SUMMERING AND BIOTYPIC DIVERSITY OF SCHIZAPHIS GRAMINUM (HOMOPTERA: APHIDIDAE) POPULATIONS ON NON-CULTIVATED GRASS HOSTS. ENVIRONMENTAL ENTOMOLOGY. 2003. V. 32(3). P. 662-667.

Interpretive Summary: The greenbug is an aphid pest of wheat and sorghum in the Southern and Central Plains States. Resistant crop varieties and hybrids have been utilized to reduce feeding damage, however their effectiveness has been diminished by the occurrence of greenbug "biotypes" which damage resistant crops. To better understand the origin of new biotypes, greenbugs living on wild grass hosts were studied in Oklahoma, Kansas, and Colorado. There was no link between the diversity of grass species and the numbers and types of biotypes present on the grasses. Few greenbugs were found on wild grasses in Oklahoma, however, grasses in Kansas and Colorado harbored greenbugs that persisted from spring to fall. A "new biotype" was found in Kansas along with three other known biotypes (G, I and K). Biotype I greenbugs were able to use many different grass species, whereas biotype G had a much narrower host range. It was determined that wild grasses may act as reservoirs for previously described and new biotypes which are then able to move into crops.

Technical Abstract: At three sites (two in OK and one in KS), all the grass species present were identified and an alpha-diversity curve was generated. Greenbugs were collected at these sites and others in Oklahoma, Kansas, and Colorado, and their hosts and biotype determined. There was no apparent link between grass diversity and biotypic diversity. At Redrock and Marshall, OK, greenbugs were only found once on non-cultivated grasses, but a fall infestation did occur in the wheat field. Hays, KS, on the other hand contained persistent greenbug populations able to use a number of grasses. At Hays the fall infestation in wheat was considerably earlier. Biotype G, I, K and a "new biotype" were found on non-cultivated hosts at Hays. Finding a "new biotype" supports the hypothesis that biotypic diversity (new combinations of virulence genes) is maintained on non-cultivated grasses, which may then act as reservoirs of virulence genes, which may enter populations found on crops. Overall Biotype I was composed of a number of clones collectively able to use a wide variety of hosts, whereas biotype G had a much more limited host range. The potential of non-cultivated hosts to provide reservoirs of greenbugs which may cause earlier fall infestation was also demonstrated.