DETERMINING PLANT RATINGS WITHOUT FIELD TRIALS 11 -- EVALUATION AND PREDICTION OF CLONAL SMUT RESISTANCE STATUS BY MORPHOLOGICAL AND SPECTROSCOPIC EXAMINATIONS OF SUGARCANE BUD SCALE SURFACES

BREEDING for increased smut resistance has become a high priority for the Australian sugar industry since the recent incursion of the disease into the Ord River Irrigation Area. Traditional screening processes are impossible in Queensland due to quarantine restrictions. Hence, potential clones are evaluated in Indonesia at considerable expense. As an alternative, the examination of bud scale surfaces both by conventional and spectroscopic means would be an attractive alternative to the traditional methods. It was hypothesised that there would be observable differences between sugarcane bud surfaces of resistant and susceptible clones, since the buds were the site of infection by the smut fungal pathogen. Scanning electron microscopy (SEM) examination of bud surfaces has uncovered a relationship between resistance status and the degree of coverage of the overall bud by the outermost bud scales. This is presently a qualitative difference between clones of a particular resistance status. However, a more quantitative result was developed using near infrared (NIR) techniques to probe bud surfaces. Initial results suggest that we can predict clonal ratings using partial least squares techniques based purely on NIR spectral data obtained from the bud surface. These techniques may develop into alternative marker systems enabling more rapid discrimination between resistant and susceptible clones within a sugarcane plant breeding program.