ASSESSING A PATHOGEN-FREE SMUT SCREEN-NEAR INFRA-RED SPECTROSCOPIC SCANNING OF AXILLARY BUDS

SMUT screening conducted in Indonesia since 1998 has provided valuable information on the resistant status of sugarcane clones, but the delay inherent in this system did not allow the crop improvement program to effect the radical changes in resistance-gene frequencies required to reduce the industry's vulnerability to sugarcane smut. This research aimed to determine whether clones could be differentiated for smut reaction using near infra-red spectroscopic (NIS) data from scans of axillary stalk buds, the portal for smut infection. The three lowest verdant-scaled buds on three stalks of 289 clones sourced from parental blocks at BSES Meringa were scanned using a contact Solvias fibre-optic probe connected to a Bruker Matrix-F spectrometer. Buds of 20 clones from two locations and all buds, verdant- and necrotic-scaled, for three cultivars of proven resistant, intermediate, and susceptible smut reaction also were scanned. Spectral data did not differentiate the clonal population into smutreaction classes, but location did affect the NIS data collected. However, collection of data from all buds of the three cultivars failed to rank the cultivars in any logical order of resistance, reinforcing the conclusion from the larger study that NIS data could not detect the chemical basis of bud-scale-based smut resistance. This failure may be because NIS best detects chemical constituents present in macro- rather than micro-constituent concentrations, particularly in high-moisture materials. Inaccuracy in the individual smut ratings averaged to provide a mean also would not assist the calibration process. This study suggests that NIS bud analysis will not provide a rapid or pathogen-free selection screen for smut resistance.