DIALLEL ANALYSIS OF YELLOW MAIZE FOR RESISTANCE TO LEAF BLIGHT (HELMINTHOSPORIUM TURCICUM PASS.) DISEASE AND SOME YIELDING TRAITS UNDER ARTIFICIAL AND NATURAL INFECTION

Eight maize inbred lines were crossed in a half diallel cross system to obtain
28 single crosses in 2002 season and evaluated plus the eight parents under two
experiments (artificial infection and natural infection). The two experiments were
carried out at Sakha Agriculture Research Stalion in 2003 season for yield/plant. ear length and percentage of resistance to leaf blight disease Under natural infection experiment. GCA and SCA means squares were highly significant for all traits except resistance to leaf blight disease. Therefor, these genotypes must be tested under artificial infection to appear their ability for resistance to leaf blight disease. Non- additive type of gene aclion was more important than additive type of gene action in the inheritance for all studied traits under artificial and natural infection conditions. The best Inbred lines for GCA effects under artificial infection were SK-7266 for grain yield/plant, SK-6241 for ear length and Gm-1004 for resistance to leaf blight disease. While, the best GCA effects under natural Infection were SK-S074 and SK-S108 for grain yield/pla"t and SK-9108 for ear length. Under artillcial infection, resistance of leaf b/ighl •. »ssase ranged from 71.5% for cross SK·6241 x SK·9108 to 100% for cross SK·6241 X SK· 7266.The cross SK-9108 x SK·9115 exhibited desirable SCA effects for grain yield/plant and resistance to leaf blight disease under artificial Infection. also. Moreover, Ihe cross SK·7266 x SK·9108 had the highest SCA effects for grain yield/plant and ear length under natural infection. Over the mean of grain yield/plant under artificial infection reduced with relative 4% compared to natural infection. The
cross SK·7285)( SK·S108 was the best cross for grain yield/plant under artificial and natural infection. While, the cross SK·6241 x SK· 7266 had higher resistance to leaf blight under artificial and natural infection,