Abstract

The study was conducted to determine the effects of cultivars susceptibility to infection with the pathogenic isolates on the pathogenicity of rice kernel smut fungus (Tilletia barclayana). Rice (Oryza sativa L.) cultivars vary in susceptibility to kernel smut disease. The susceptibility of 18 commercial rice cultivars to T. barclayana was evaluated. Moreover, pathogenicity of 46 isolates of T. barclayana which had been isolated from six governorates in Egypt was studied using Giza 178 rice cultivar and Hybrid 1. The activities of certain oxidative enzymes, e.g. peroxidase (POX) and polyphenoloxidase (PPO) and total protein were determined in healthy and inoculated cultivars. Intron-exon splice junctions (ISJ) protocol was used to study the relationship among rice cultivars differing in their susceptibility to infection with the pathogen. Results showed that Giza 178 rice cultivar and Hybrid 1 were the most susceptible cultivars for rice kernel smut disease. Isolate no. 35 from the pathogenic fungus was the most aggressive isolate. Additionally, an increment in the defense-related enzymes and total protein was observed in rice cultivars as a result of inoculation with T. barclayana. ISJ technique showed the relationship between the studied rice cultivars and lines upon susceptibility to T. barclayana. It can also differentiate between the isolated T. barclayana isolates upon virulence on the studied rice cultivars and lines.

Key words: Rice kernel smut disease, intron-exon splice junctions, rice, enzymes activity.