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

(Table 3). This prompted the use of multivariate analysis to identify themajor genotypic patterns. The fi rst three principal components witheigenvalues ≥0.3 under both Striga-infested and Striga-free conditionssummarized 72% of the multivariate variation in inbred means (datanot shown) and were the most important. The traits loaded on thethree axes were used for the grouping of the inbred lines. The inbredlines evaluated under Striga infestation were clustered using grainyield, days to 50% silking, plant height, EPP, ASI, Striga emergencecounts and damage rating (Fig. 1). On the other hand, the inbredlines evaluated under Striga-free conditions were grouped based ongrain yield, days to 50% silking, plant height, EPP and ASI (Fig. 2). Theresulting dendrograms generated four main groups for the inbredlines under Striga infestation and six main groups under Striga-freeconditions. Under Striga infestation, group 1 was represented by 17inbred lines; group 2 by 11 inbred lines; group 3 by one inbred line(inbred 6) and group 4 by six inbred lines. Ten of the inbreds in group1 had white endosperm color and were derived from TZEE-W SR BC 5× 1368 STR; two had white endosperm color and were extracted fromTZEE-W Pop while the remaining fi ve lines had yellow endosperm andwere derived from TZEE-Y SR BC 1× 9450 STR. Group 2 containedinbred lines derived from two germplasm sources, TZEE-W SR BC 5×1368 STR and TZEE-Y SR BC 1× 9450. The extra-early inbreds weregrouped into six major clusters under Striga-free conditions (Fig. 2).The number and type of inbred lines in the different clusters underStriga-free conditions were different from those in the correspondingclusters generated under Striga infestation. As under Striga infestation,the inbred lines in clusters 1, 2 and 4 were derived from differentsource populations. It is interesting to note that in some cases someinbred lines derived from the same germplasm sources were placedin different clusters while in others they were grouped together. Forexample, inbreds derived from TZEE-W SR BC 5× 1368 STR werefound in all groups under both environments. On the contrary, all theyellow endosperm inbred lines derived from TZEE-Y SR BC 1× 9450STR (31, 32, 33 and 34) were placed in group 1 under both Strigainfestedand non-infested conditions. Furthermore, inbreds 20 and 21derived from TZEE-W Pop were both placed in group 1 under Strigainfestation while inbred 20 was placed in group 1 and inbred 21 ingroup 5 under Striga-free conditions.The results of this study indicate that the clustering of the inbredlines under Striga infestation was in some cases dependent on thegermplasm source from which they were derived while in somecases the grouping was independent of the genetic background.Furthermore, the yellow endosperm inbred lines were classifi ed intoone group suggesting that probably there is no genetic diversity among37