Quantitative genetics of sugarcane : IV. Genetics of Fiji disease resistance.

1. Fiji disease is an important virus disease of sugarcane in many countri es. In Fiji, its vector is the leafhopper Perkinsiella vitiensis. 2. The usual measure of resistance under insectary test conditions is the number of days required after exposure to viruliferous hoppers for half the test plants of a clone to show the diagnostic symptoms (SD50). Previous studies have shown this measure is related to resistance under field conditions and is convenient to record. 3. A quantitative genetic analysis has been made of resistance to Fiji disease in a hybrid sugarcane population. 4. The SD50 measure of resistance showed a heritability and repeatability of about 0.4. These results indicated that Fiji disease resistance can be improved by breeding and selection. 5. No unfavourable correlations were detected between resistance and other commercial attributes. 6. In a mixed stand, sugarcane clones differ for the number of leafhoppers found on them. However no necessary relationship was detected between this character and resistance to Fiji disease.