RESISTANCE MECHANISMS OF PI-240675 RYE TO BIOTYPE-F GREENBUG

Previous research identified a rye accession, P.I. 240675, as resistan t to greenbug biotypes B, C, E, and F. Rye is crossable with wheat and can be utilized by breeders to develop resistant wheat. The purpose o f this research was to select biotype F-resistant seedlings of P.I. 24 0675 and to compare mechanisms of resistance of P.I. 240675 with those of 'Insave F.A.' rye and 'Century' wheat. The results from all tests showed that P.I. 240675 exhibited the highest level of resistance of t he three entries in the study, and had a relatively high degree of ant ibiosis, antixenosis, and tolerance. The plant resistance index (PRI), which combines values from the three resistance mechanisms, was great est for P.I. 240675 with a PRI of 10.56, followed by Insave F.A. and C entury with values of 1.92 and 1.66, respectively. Although antibiosis to biotype F was detected in Insave F.A., this entry had low levels o f antixenosis and tolerance and is not a good source of biotype F resi stance. P.I.240675 can be used by plant breeders as a source of resist ance to greenbug biotypes B, C, E, and F in rye and species related to and crossable with rye, including wheat.