Author
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Marchetti, Marco |
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LAI, X-H - TEXAS A&M UNIV |
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Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 12/1/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Among the sources of Pi-genes to U.S. rice were Rexoro (Pi-I), Zenith (Pi-z and Caloro (Pi-ks). All three varieties were selections from introduced oriental rices. In the 1960s, most of the southern cultivars possessed one or two of these Pi-genes, and during that period only races ID-13, IG-1 and IH-1 were found commonly. In 1965, a new gene, Pi-kh, was introduced in the ecultivar Dawn which was used later as a parent in several breeding programs. Consequently, the Pi-kh gene was present in many later releases, including Newbonnet, Lemont, Gulfmont, and Cypress. As Pi-kh provides resistance to the above-named races, these were replaced in prevalence by races IC-17 and IB-49. In response to the severe blast damage by IB-49 and IC-17 to Newbonnet in Arkansas in 1986-87, the cultivar Katy was released in 1989 with other new resistance genes, including Pi-ta2 from the blast-re sistant Indochinese variety Tetep. Katy and its derivatives, Kaybonnet and Drew, revealed the presence of new races, IE-1K and IC-1K (the "K" indicated atypical versions of the races which attack Katy), the only U.S. races virulent against Katy. In 1997, Jefferson, with Pi-kh, Pi-z, and pi-d was released, with the knowledge that it was susceptible to race IB-49, but resistant to IE-1K and IC-17. The few isolates obtained from Jefferson were not of race IB-49 but of rarely seen IB-17 and a new race IB-1J (an atypical version of race IB-1 which attacks Jefferson). The capacity of P. Grisea to accommodate changes in host resistance genes is formidable and will present an ongoing challenge to breeders. |
