GENETICAL DIVERSITY OF RESISTANCE IN POTATO GENOTYPES FOR WAX LAYER TO BROWN SPOT DISEASE

Brown spot of potato, is the most common and major diseases of potato in the most growing regions, incited by different species of Alternaria, remains an increasing threat to Thepathogens have a wide spectrum of host plants throughout the world, including Iran. Methods for disease prevention and control are based on combining agricultural management practices with chemical control. Using disease free seeds or seeds and plants treated with fungicidescan greatly reduce disease incidence. After appearance of the first symptoms of disease, stringent fungicide spray program is an effective way to reduce losses. Many authors seem toagree, that the most economically feasible method of disease control is the development ofresistant potato crops varieties, as transgenic approach proved unsuccessful. Due to our increasing understanding of pathogen - host plant interactions, identification of resistancesources, and assessment of the resistance trait inheritance mode, breeding programs of Potatocrops for Alternaria resistance can be enhanced. This is of particular importance since recentyears’ experience dynamic development of ecological and integrated plant production with anemphasis on plant biotic stress resistance. Highly resistant genetic resources have not been reported in potato cultivated species, although some varieties differ in theirresistance/susceptibility level. Wax layer plays an important role as far as the resistance todiseases is concerned. This study assessed levels of susceptibility surveyed and analyzed in ten potato cultivars; Boren, White Desiree, Picasso, Ramus, Kaiser, Markiz, Granola,Kennebec, Cosima, Preemie; thickness of the leaf wax layer along with the correlation withresistance was. The thickness of wax layer in upper and lower surface was measured. Theresult indicated that, there was a positive co-relation between the wax layers with variousrange of susceptibility. Boren and White Desiree with the highest mean of wax thickness 1.48 and 1.41 microns were the most resistant ones respectively. Also, Preemie and Cosima with the lowest means of 0.81 and 0.89 microns were the susceptible respectively. Although theother cultivars are intermediated in between, and in their own statistical groups. These results revealed that thickness of wax layer plays an important role on inhibitory to the disease infection, as far as the resistance is concerned.

کلیدواژه ها:

Alternaria sp. ، wax layer ، potato ، Iran