Physical And Chemical Characteristics Related To Lodging Resistance In Wheat

Stem lodging resistance has become increasingly prominent in context of searching for high yield in wheat as lodging threatens the wheat productivity to serious levels.Characterization of wheat stem is a crucial factor to determine lodging resistance.Hence,the deep study of structural characteristics of the wheat stems has greater implications for improved lodging resistance and higher grain yield.Present study aimed to explore the physical,chemical and morphological characteristics of wheat stem in relations to breaking strength.Also,we studied the stem characteristics of brittle culm mutants of wheat,and made a preliminary analysis of their genetic characteristics.Then we constructed the F2 populations for map-based cloning.Here are main points proposed in the study:Part 1:It was concluded that the stem breaking strength showed highly significant correlation with some agronomic traits such as fresh weight,2nd internode width,width of flag leaf and spike weight.Highly significant correlation between the two years for different agronomic traits indicated the existence of genetic diversity and stability among the wheat germplasm.Two representative groups,with the highest(group ?)and the lowest breaking strength(group ?),on the basis of stem breaking strength exhibited significant difference however,least differences were observed in lignin content.Although,group? had significantly higher levels of G,H monomer proportion and cellulose as compared to group ?,however the S monomer proportion and Xyl of group ? were reduced significantly.Therefore,it was asserted that G,H and total cellulose influences positively to improve the stem breaking resistance in contrast to S monomer and Xyl which effect negatively.Furthermore,marked differences were observed in the number of small vascular bundles(SVB)than large vascular bundles(LVB)between the two groups.Conclusively,the presence of fewer number of SVB in group ? indicated that the stem breaking resistance can be improved as a result of increased number of SVB.Part 2:Chemical assay of brittle culm mutants and their wild types suggested that crystalline cellulose improve the stem rigidity in contrast to hemicelluloses which impaired the stem breaking resistance as brittle culm mutants demonstrated the reduced breaking strength and cellulose along with increased hemicelluloses levels.These results are in line with the findings of the first experiment.Similarly,higher biomass enzymatic digestibility than wild types upon 1%NaOH pretreatment exhibited by the mutants verified the possibility for their application in breeding for energy crops.On the other hand,segregation ratio of culm traits in F1 and F2 populations from the cross between brittle culm mutants and Yangmai 158 suggested that wbc1?wbc2?wbc4?wbc5 and wbc6 were controlled by a single recessive gene,whereas wbc3 was controlled by a single dominant gene.However,further investigation in the regulation mechanism of cell walls and map-based cloning is required for their potential use in the breeding programs for improving wheat yield and their prospective role as energy crop.