COMPARISON OF QTLS MAPPED IN RILS AND THEIR TEST-CROSS PROGENIES OF TROPICAL MAIZE FOR INSECT RESISTANCE AND AGRONOMIC TRAITS

Quantitative trait loci (QTL) affecting resistance to south-western co rn borer Diatraea grandiosella (SWCB) and sugarcane borer Diatraea sac charalis (SCB) have been identified previously in F-2:3 lines and rec ombinant inbred lines (RILs) of tropical maize using restriction fragm ent length polymorphism (RFLP) analyses. Our objective was to determin e whether QTLs identified in these generations are also expressed in t est-crosses (TC) of RILs. A population of 166 TC progenies was develop ed by crossing RILs from the cross CML131 (susceptible) x CML67 (resis tant) with the unrelated, susceptible tester line CML216. Resistance t o first-generation SWCB, measured as leaf-feeding damage (LFD) under a rtificial infestation, and other agronomic traits were evaluated in tw o environments for the TC progenies and three environments for 183 RIL s. The correlation between line per se and TC performance was low for LFD and intermediate for most agronomic traits. Estimates of the genot ypic variance and heritabilities were smaller in the TC progenies than in the RILs for all traits. Quantitative trait loci were identified u sing an RFLP linkage map with 136 loci. For LFD, four QTLs were detect ed in the TC progenies, of which two were in common with nine QTLs pre viously mapped in the RILs. Few QTLs for agronomic traits were common to the two types of progeny, because of the low consistency of QTL pos itions for all traits in RIL and TC progenies, the use of TC progenies should be considered in QTL mapping studies as the first step for mar ker-assisted selection in hybrid breeding.