Genetic control of banded leaf and sheath blight (Rhizoctonia solani f. sp sasakii) in maize (Zea mays L.)

One of the main deterrents to high grain yield in maize is its susceptibility to several diseases. Banded leaf and Sheath blight (BLSB) caused by (Rhizoctonia solani f. sp. sasakii) has become a serious threat to its cultivation in the north -western plains of India. The pathogen spreads from the basal sheath to the developing ear under favourable environmental conditions. The developing ear is completely damaged and dries up prematurely with caking of husk leaves. The main objective was to work out the inheritance of resistance to this biotic stress. Inheritance of resistance to BLSB was studied based on the analysis of 10 crosses, Eight crosses were between 2 resistant (CM104 and CML1) and 4 susceptible (Tarun circle times- 36-1-1-1-2-1-4, D741 circle times- 1-1-1-10-4-4, Pop31 circle times-21-1-2-4-1-1-5-1/13 # and Tarun circle times- 252-1-2-2-1-2-1) inbred lines. In addition, one resistant x resistant and one susceptible x susceptible crosses were also studied. Parents, F-1's, F-2's and backcrosses were included in the present study. Final evaluation was undertaken under artificially created epiphytotic conditions. The F-2 segregation pattern for BLSB reaction was 15:1 in crosses involving CM104 as resistant parent and 13:3 in crosses involving CML1 as resistant parent. The BC1 P-1 segregation pattern exhibited3:1 ratio. The resistant x resistant and susceptible x susceptible crosses followed all:0 and 0:all for resistance and susceptibility, respectively. The F-2 segregation analysis of eight susceptible x resistant crosses revealed that resistance was governed by two genes. The BLSB reaction in F-2 and backcrosses involving CM104 and susceptible lines suggested that resistance in CM104 was controlled by duplicate dominant genes while crosses of CML1 showed dominance and recessive interaction.