EVALUATION OF VARIETAL RESISTANCE AND PHYSIOLOGICAL CHARACTERS OF FALSE AND KERNEL SMUT DISEASES OF RICE IN EGYPT

Abstract

Rice false and kernel smuts are worldwide diseases present almost in rice ecosystems. Smut diseases are new production constrains. In Egypt, these smuts were considered a minor disease. False smut infects some grains of the panicle causing a yield loss. In addition, it produces ustiloxin which is a poisonous toxin to humans and other animals. Kernel smut also reduces the yield and quality of grains. The present study aimed to determine the resistance of number of rice genotypes against both false and kernel smut. Also study the physiological characters of the isolated fungi. Twenty three Egyptian rice genotypes were used in this investigation under field conditions in Sakha experimental farm during the 2009 and 2010 rice growing seasons. In case of false smut, all tested varieties were susceptible with different level of susceptibility as Giza 171, Giza 172, Giza 177 and Giza 178 were highly susceptible although Giza 171 and Giza 172 as late mature and Giza 177 is an early maturing variety. Data presented here show a wide range of variability in the response of different rice types against false smut infection. The resistance level of Japonica type against the disease was ranged from 20.37 to 92.90 %. While, the resistance level of Indica rice was ranged from 68.15 to 83.21 %. Also hybrid rice showed similar Indica rices behavior whereas their resistance level ranged from 66.82 to 81.88 %. In case of Indica- Japonica rice resistance were ranged from 54.01 to 88.06 %. The resistance of GZ lines ranged from 67.68 to 92.04 %. The widely cultivated varieties, Sakha 101 and Sakha 104 showed to be more resistant than other cultivars and exhibit significant a degrees of field resistance to false smut (92.90 %) compared with highly susceptible cultivar Giza 171. Regarding to kernel smut, Giza 171, Giza 172, Giza 159, Giza 177 and Giza 178 were the most susceptible tested cultivars. While Sakha 101, Sakha 104, GZ6522, GZ7955, Giza 182 and the Egyptian Yasmine were moderately resistance cultivars presenting over 90 % disease recovery. The physiological studied showed that false smut was grown abundantly on rice bran agar medium with fairly sporulation, while potato sucrose agar showed to be the most suitable medium for growing kernel smut fungus. The isolates of both fungi exhibited different level of variability. False smut isolates were differed in their colors with a range from olive to white or orange, while kernel smut isolates differed in pigments production with a range from violet or purple up to reddish color.