Asian Research Thesis Index

Abstract

Thirty genotypes of wheat (Triticum aestivum L.) developed by different wheat research institutes/ stations of Pakistan were evaluated for grain production and quality characters at PMAS-Arid Agriculture University Rawalpindi, Pakistan. Medium to high genetic diversity was seen for number of days to heading, maturity days, time required for filling of grain, plant height tillers/ m2, spikes / plant, spikelets count/spike, grains/ spike, one thousand grain weight, grain production /plant, grain moisture content, ash content, protein content, wet gluten and lysine content. These genotypes were classified into four clusters on the average linkage basis. Cluster I comprised of nine genotypes including four approved wheat varieties. Genotypes in first cluster possessed greater mean values for grain (Number/ spike, grain production/ plant, protein content, wet gluten and lysine content). Cluster II contained early maturing genotypes taking less grain filling period. Wheat genotypes in cluster III were late in flowering and maturity, whereas, genotypes in cluster IV had small stature, less spike number /plant, less grain number / spike and were also poor yielder. Eight contrasting genotypes were selected on the basis of yield and quality characters and crossed in all possible combinations to ascertain the genetic basis of variation. Results of genetic examination exposed the pronounced effects of additive variance for number of days to heading, grain filling period and grains /spike. Variance component (additive & dominance) were playing their role in the manifestation of maturity, plant tallness, tillers number in each plant, spikes in each plant, spikelets in each spike, grains number / spike, one thousand grain weight, grain production and all quality characters. Maternal effects were also observed in most of the cases. Graphical representation exhibited the involvement of partial dominance for all the characters under study, except spikelets number / spike and ash content. Spikelets number was controlled due to over dominance of gene. Scaling tests did not validate the data set of ash content for further examination i.e. estimation of genetic parameters and graphical examination. Coefficients of genotypic and phenotypic variation and heritability estimates were computed in F2 population of 8 x 8 diallel cross of wheat. Results exposed higher magnitude of genotypic variances in case of plant height, one thousand grain weight and grain production /plant. The coefficients were low for lysine content and protein content and moderate for other characters. Heritability estimates were generally high for all characters and expressed the significance of additive gene effects. The F2 data were analyzed for correlation and path coefficient analyses. Number of days to heading, maturity, plant height and weight of one thousand grains were positively linked with grain production, whereas the correlation of grain production with lysine content and protein content was negative. The results of path coefficient examination exposed that maturity days, spike number /plant and one thousand grain weight directly and positively influenced the grain yield. The direct effects of number of days to heading, plant height, protein content and lysine content on grain production /plant were negative.

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