Submitted to: Sugar Cane International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2004
Publication Date: 1/20/2005
Citation: Schenck, S., Pearl, H.M., Liu, Z., Moore, P.H., Ming, R. 2005. Genetic variation of ustilago scitaminea pathotypes in hawaii evaluated by host range and AFLP markers. Sugar Cane International. 23(1):15-19.
Interpretive Summary: Of the various sugarcane diseases, smut disease caused by Ustillago scitaminae causes the greatest yield losses and is the most difficult to control through producing host genetic resistance, in part because the pathogen occasionally produces a new race that overcomes prior host resistance. A collaborative project between the Hawaii Agriculture Research Center and the ARS, Pacific Basin Agricultural Research Center was conducted to determine the variability and distribution of sugarcane smut races in Hawaii by analyzing AFLP DNA sequence differences among three Ustillago species (smuts of barley, corn, and sugarcane) and isolates of sugarcane smuts showing differential host susceptibility. DNA difference at the level of AFLPs was small and unable to distinguish between the new race and old isolates of the sugarcane smut pathogen. The failure to develop a fast diagnostic for sugarcane smut races means growers must continue to rely on more expensive and time consuming measure for disease control, breeders must increase testing for reaction for multiple races, and it may become necessary for researchers to explore alternative methods such as single nucleotide polymorphisms to distinguish sugarcane smut races.
Technical Abstract: A new sugarcane smut race that infected the previously resistant cultivar H78-7750 appeared in Hawaii in 2001. It was subsequently shown that many of the Hawaii sugarcane cultivars differed in susceptibility to the old and new Ustilago scitaminea races. The objective of this study was to assess the genetic diversity between the old and new races using DNA markers. Molecular diversity of U. scitaminea and other fungal species was analyzed by amplified fragment length polymorphism (AFLP) markers. Thirty-seven U. scitaminea isolates and five isolates of other fungal species were fingerprinted with 310 AFLP markers. High genetic similarity was detected among the isolates from the old and new U. scitaminea races, but little was detected among the different Ustilago species. Cluster analyses did not clearly separate the new race from the old race, suggesting that the new race might have arisen from a single mutation event in the genome of the old race. DNA fingerprinting clearly differentiated all Ustilago species and indicated that U. scitaminea is probably more closely related to U. hordei than to U. maydis.