Demand-Driven Technologies for Sustainable Maize ... - IITA

66S. hermonthica and S. asiatica. Yield losses of Striga-infested crops canrange from 50% to more than 90% (Lagoke et al. 1991; Ransom etal. 1990; Kim 1991; Kim et al. 1997). Control of the parasitic weedis very complex and diffi cult. Host plant resistance has been foundto be effective and relatively cheap from the viewpoint of resourcepoorfarmers in the West and Central Africa (WCA) sub-region. It has,therefore, been recommended that any effective Striga control strategymust include host plant resistance (Robinson and Dowler 1990; Kim1991; Kim and Winslow 1991; Kim and Adetimirin 1995; Adetimirinet al. 2000a, b).Some maize varieties have demonstrated partial resistance to Strigaunder fi eld conditions. The varieties supported fewer fully developedStriga plants (Ransom and Odhiambo 1995) while other varieties havedemonstrated Striga tolerance by supporting growth of many plantsof the parasite with little or no reduction in grain yield (Kim 1991;Kim and Adetimirin 1995). However, maize varieties that completelyprevent successful development of S. hermonthica are presently notavailable. Lane et al. (1997) reported that such resistance exists in Zeadiploperennis Iltis, Doebley and Guzman (Iltis et al. 1979).The present study involved inbred lines derived from Z. mays x Z.diploperennis crosses. The objective of the study was to determine themode of inheritance of resistance to S. hermonthica among the newmaize inbred lines, using diallel analysis.Materials and MethodsA 10 x 10 diallel cross involving ten inbred lines was made and theresulting 45 single-cross hybrids were evaluated at Abuja (4°25’ N,7°33’ E) and Mokwa (9°30’ N, 5°07’ E) in Nigeria, Ina (9°30’ N, 2°62’E) and Angaradébou (11°33’ N, 2°13’ E) in the Republic of Benin.Field evaluations were carried out in the two countries during themajor rainy season in 2001 and 2002.Five of the inbred lines were derived from crosses between Z.mays x Z. diploperennis, one line was derived from TZL Comp.1 andfour were standard inbred checks (Table 1).The F 1hybrids were evaluated in infested and non-infested plots,which were adjacent and separated by a 1.5 m alley. Alpha latticedesign with three replicates was used. A pair of infested and noninfestedplots was planted with each F 1hybrid. Proximity of theinfested and non-infested plots provided the basis for a valid estimateof yield loss due to Striga infestation. Striga seeds used for the trialswere collected in the previous year from each of the locations. Plotsconsisted of single rows, each 5 m long spaced 0.75 m apart. Maizeseeds were planted at 0.25 m interval within each infested and noninfestedrow. Artifi cial Striga infestation was achieved by applying a