ABSTRACT

Commercial cotton cultivars in Australia vary in their resistance/susceptibility to Fusarium wilt. Cotton growers, agronomists and consultants requested the development of a system that would provide a quantitative measure of the relative resistance or susceptibility of new or existing cotton cultivars to Fusarium wilt. A Fusarium Resistance Ranking protocol was developed and growers are using the ranking when selecting cultivars to grow in areas where the disease is present. The protocol is described along with assessment methods and the methods for calculating the ranks. The proportion of plants surviving throughout the season with little or no disease is used as a measure of the resistance of a cultivar and is expressed relative to an industry standard cultivar that is assigned a value of 100. The number of field comparisons contributing to the ranking is indicated in brackets. For example, if a cultivar has a Resistance Rank of 129(5) it indicates that the averaged results of five field experiments have shown that the cultivar is 29% better (more resistant) than the standard. This Resistance Ranking protocol provides a means of measuring the progress being made by plant breeders in their attempts to produce cultivars with higher levels of resistance.