Plant & Animal Genome VI Conference

P37

ISOLATION AND CHARACTERIZATION OF GENES ASSOCIATED WITH ENHANCED TOLERANCE TO PHYTOPATHOGENIC FUNGI IN COTTON

Cooperative Research Centre for Sustainable Cotton Production, School of Biological Sciences A12, The University of Sydney, NSW 2006, Australia.

Disease caused by phytopathogenic fungi such as Fusarium oxysporum and Verticillium dahliae can inflict significant losses on cotton crops and, if not adequately controlled, could adversely affect the long-term viability of the cotton industry. We are investigating natural mechanisms of enhanced disease tolerance which exist in elite cotton cultivars from the two major fibre-producing species Gossypium hirsutum and G. barbadense. Two strategies have been pursued to identify candidate genes. Firstly, a cDNA library produced from the roots of cotton seedlings shortly after infection with V. dahliae has yielded a number of clones which represent infection-regulated cotton plant genes. Expression profiles of some of these genes indicate that they are transcribed more rapidly and/or to higher levels in cultivars which exhibit greater tolerance to fungal disease, thereby implying a potential role for these genes in disease amelioration. Amino acid sequence homology searches have confirmed the isolation of various pathogen response genes together with genes which may be involved in pathogen recognition and signal transduction. Secondly, the isolation and cloning of plant disease resistance gene analogues, using consensus primers designed to match the nucleotide binding sites from disease resistance genes of other plant species, has resulted in the identification of several classes of these genes in cotton. Further characterization of the disease resistance gene analogues with respect to genome organisation and allelic variation may also reveal an association of these genes with enhanced cotton plant tolerance to biotic disease.