ENHANCE RESISTANCE TO ALTERNARIA ALTERNATA CAUSING POTATO BROWN LEAF SPOT DISEASE BY USING SOME PLANT DEFENSE INDUCERS

Abstract: Host resistance is an efficient and effective component in integrated management of plant diseases. The aim of this study was to test whether Acibenzolar-S-methyl (ASM), Chitosan, Heads-up and Acetyl Salicylic Acid (ASA), known to induce resistance against various diseases, can help protect potato crop against brown leaf spot. The effect of these inducers, on two potato cultivars, Goldrush and FL1879 against Alternaria alternata, causal agent of brown leaf spot at two different field sites were evaluated. To determine the effects of the application of inducers on disease resistance, the foliage of the potato cultivars was sprayed with appropriate concentrations of ASA, chitosan, and ASM. Heads-up was also applied as a pre-plant treatment on potato tubers. The results obtained from the both field experiments indicated the highest yield performance was achieved in plots treated with ASM, followed by Heads-up and chitosan treat-ments. However, no significant difference in terms of tuber yield production has been noted between ASA treated potato foliage, and the untreated control plants. Results of experiments with detached leaves showed that there was a significant difference regarding disease index reduction between plots which been treated with defense inducers and untreated, inoculated plots. It was clear that on both po-tato cultivars, application of chitosan and ASM encouraged enhancement of the disease resistance compared to the ASA and Heads-up treatments. In the laboratory experiment, disease progress was recorded on leaves from three different heights of the crop canopy. The results indicated that disease severity was low in the apex, moderate in the middle and high in the lower parts of the crop, in both potato cultivars. These results suggest that chitosan and ASM may offer alternative methods for controlling brown leaf spot of potato