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RESISTANCE ASSESSMENT OF SUGARCANE CULTIVARS TO Ustilago scitaminea IN THE FIELD AND DETECTION OF THE FUNGUS IN TISSUE CULTURED PLANTLETS

Plantlets of sugarcane cultivars L62-96 (susceptible), CL 73-239 (moderately susceptible) and CP73-21 (resistant) were generated by in vitro apical meristem tissue culturing. Plantlets were then inoculated with mixture of two types of sporidia and/ or dikaryotic mycelial suspension. Ratoons of the same cultivars were also inoculated and planted in the field. In the field, infected whips were developed in 33.8% and 15.9% of the plants of the susceptible and moderately susceptible cvs., respectively. No symptoms were observed in the resistant cvs. However DNA of Ustilago scitaminea was detected by PCR, - in tissue extracts from below and above the site of inoculation and also from suckers,-in all cvs.(susceptible as well as resistant) of the in vitro inoculated plantlets. Based on the results of this study, detection of the fungus in the tissue cultured plantlets by PCR cannot be used for assessment of resistance or susceptibility to U. scitaminea of sugarcane cvs in vitro.