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Title: PLANT RESISTANCE COMPONENTS OF TWO GREENBUG (HOMOPTERA: APHIDIDAE) RESISTANT WHEATS (REV. TITLE, ADD ACC. DATE)

Author
item Webster, James
item Porter, David

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The greenbug is the most important wheat pest in the Southern Plains. Planting greenbug-resistant varieties is an ideal management strategy for crops with a low profit margin, such as wheat. In addition, many pesticides currently recommended for greenbug control may be banned due to environmental concerns. Wheat breeders and entomologists have developed resistant varieties and germplasm lines, but some of their efforts have been hampered by the occurrence of new greenbug biotypes that damage the resistant sources. Researchers are constantly searching for new sources of resistance in wheat to the greenbug. Largo and GRS 1201 are two germplasm lines that have been developed with resistance to the three predominant Southern Plains greenbug biotypes: E, I, and K. Each source has agronomic and end-use quality advantages and disadvantages for the breeder to consider in selecting a greenbug-resistant parent line. Therefore, we compared these two lines to determine their levels of resistance against biotype E. Several aphid and plant measurements, including the total number of aphids produced on each plant, plant selection preferences by the test aphids, and ratings of plant damage caused by aphid feeding were recorded for each plant entry. GRS 1201 had a much higher level of combined resistance components than did Largo. The results from these tests provide additional information for breeders to consider in selecting a greenbug- resistant breeding line.

Technical Abstract: Several biotypes of the greenbug (Schizaphis graminum (Rondani)) attack winter wheat (Triticum aestivum L.) in the Southern Plains every year. Two wheat germplasm sources of resistance (Largo and GRS 1201) have been developed that provide protection against the three predominant greenbug biotypes (E, I, and K). Each source has agronomic and end-use quality advantages and disadvantages for the breeder to consider in choosing a greenbug-resistant breeding line. We compared these two germplasms to determine their levels of resistance against biotype E. Components of resistance (i.e., antibiosis, tolerance, and antixenosis) were measured on seedlings of GRS 1201, Largo, and 'TAM W-101' (a susceptible control). Several aphid and plant measurements (e.g., total number of aphids produced per plant, plant damage ratings, and selection preferences) were recorded for each plant entry. Select data recorded for each resistance component were normalized and combined to derive a Plant Resistance Index (PRI) for each wheat entry. Results of this analysis indicated that GRS 1201, with a PRI of 90, has a much higher level of combined resistance components than did Largo, with a PRI of 25. TAM W-101, the susceptible control, had a PRI of 1. These data provide additional information for the breeder to consider in selecting a greenbug-resistant breeding line.