GENETIC DIVERSITY IN Ug99 TOLERANT EXOTIC BREAD WHEAT GENOTYPES

Abstract

Wheat is the second important cereal crop in Bangladesh and its consumption is increasing day by day but production is decreasing. Production decrease is mainly due to area reduction for strong competition with high yielding Boro rice, Maize, Potato and vegetable crops. High temperature at grain filling stage and Bipolaris leaf blight disease are the major problems of low yield. Besides that, a new virulent race of stem rust TTKSK (Ug99) identified in Uganda in 1999 has already reached up to Iran. So, it may comes to Bangladesh also; therefore, the experiment was conducted at the Wheat Research Centre, Nashipur, Dinajpur with 29 Ug99 tolerant wheat genotypes collected from International Maize and Wheat Improvement Centre, Mexico with widely adapted variety BARI Gom 21 (Shatabdi) during 2009-2010 to study their variability and select parents for hybridization programme. There was significant variation for all the thirteen characters studied indicating the presence of considerable variations for selection. All the genotypes were earlier in heading than Shatabdi. Many genotypes had higher yields, 1000-grain weight, spikes/m’, harvest index and agronomic score. Correlation study revealed that spikes/m’, biomass and agronomic score were positively correlated with yield. Thousand grain weights were also positively and significantly correlated with plant height, grains/spike and grain filling duration. Waxiness, grain filling duration and grain yield had high genotypic coefficient of variation coupled with high to moderate heritability and genetic advance. So, selection on the basis of these characters will be highly effective. Eigen values of thirteen principal axes and percentage of total variation revealed that first axis accounted 30.69% and first two axes 56.25% variation among the genotypes. Thirty genotypes were distributed into five clusters with one genotype in group III tol0 genotype in group V. The highest distance from cluster I was cluster III followed by cluster V. Inter genotypic distance between pairs of genotypes varied from 0.1014 to 1.1507 indicating the presence of considerable variability in the genotypes. The highest distance was 1.1507 from Shatabdi to E28 followed by Shatabdi to E30 (1.1068). So, hybridization of E28 and E30 with Shatabdi will give maximum advantage. Inter-cluster distance was higher than intra-cluster distance indicating that genotypes of different clusters were more diverse than those of within cluster. Intra-cluster means for yield, spikes/m’, harvest index and agronomic score was the highest and heading days was the lowest. All these factors are positive for Bangladesh condition. So, use of these genotypes in breeding programme will give good output. Spikes/m’, biomass and harvest index had both vectors positive. So, these characters had the highest contribution towards the divergence among 30 Ug99 tolerant genotypes. Vector I was positive for heading days, plant height, grains/spike, 1000-grain weight and grain filling duration. Vector II was positive for maturity days and grain filling duration. These characters had also good contribution towards the divergence of the 29 Ug99 tolerant genotypes.