Breeding Strategy for Rice Blast Resistance in Egypt

Abstract

Rice blast disease caused by the fungus Pyricularia grisea is one of the most biotic stresses constrains in rice productivity in Egypt. Breeding for blast resistance are our concern in varietal improvement program. Since the Egyptian cultivars were showing susceptibility. Understanding gene type, mode of inheritance and stability of the resistant varieties are essential for transfer the blast resistance to popular cultivars. The previous studies for exotic and local rice varieties under Egyptian conditions showed that inheritance of blast resistance was dominant in most cases and one to three major genes controlled the mode of resistance.

Our strategy for breeding to blast resistance are: 1) gene accumulation resulted of introducing two leading rice cultivars, Sakha 101, and Sakha 102; 2) gene pyramiding resulted of introducing the high yielding rice variety Giza 178; 3) gene rotation where resistance cultivars are concentrated in hot spots in Nile Delta. Multiline varieties is another strategy but still under evaluation. The level of partial resistance is under our concern in all strategies.

The stability of resistance of the twenty Egyptian rice cultivars to leaf blast caused by Pyricularia grisea was studied using three stability parameters viz. Low mean disease score, small regression coefficient and least deviation values from regression. Cultivars like IR 28, Sakha 101, Giza 178, Giza 175, Sakha 102, and Giza 181, showed low mean disease score (1.71,1.80,1.84,1.88 respectively ),and small regression coefficient values ranged between (0.03 and 0.26) as well as least deviation from regression. Therefor these cultivars were found to show stable resistance to leaf blast and can be used as new sources for blast resistance in breeding program.