β Scribed by K.H.M. Siddique; B.R. Whan
No coin nor oath required. For personal study only.
Earlier studies showed that the ratio of the weight of the wheat ear to stem at anthesis (ear :stem ratio) may give a better indication of potential yield than harvest index because it is determined early in the life cycle and is not affected by post anthesis stress . These studies concluded that selection for high ear:stem ratio at anthesis may lead to further improvement in grain yield of wheat . The present work was undertaken in the field to identify lines varying in ear : stem ratio in breeding populations and to study its implications for yield improvement .
At anthesis stem length, ear length, tiller number, dry weight of stem and ear and ear :stem ratio were measured in 14 crosses on F2 single plants and F2 derived lines grown in the F3, F4, and F5 at three locations in Western Australia over four seasons . In addition, biomass, grain yield and yield components were measured on selected crosses at two locations on F2 derived lines grown in the F4 and F5 . There was a considerable range of ear :stem ratio between and within the crosses studied . Although ear :stem ratio was strongly correlated with stem length, there was substantial variation within stem length classes . Ear :stem ratio had a high mean broad sense heritability (82%), whereas HI, grain yield and above ground biomass had lower heritabilities, 68, 55 and 35% respectively. Ear :stem ratio was strongly correlated between generations and sites indicating stability of this character . Ear :stem ratio had a significant positive correlation with grain yield, HI, grains per ear and per m 2 . The correlation of grain yield with HI was equal or slightly higher than that of grain yield with ear:stem ratio .
Ear: stem ratio offers promise as a predictor of HI and yield potential where post-anthesis moisture stress can influence HI . Ear :stem ratio measurement is unlikely to be adopted for selection purposes in routine breeding programs, as it is laborious and time consuming . However, ear : stem ratio could be used to identify superior parental genotypes and early generation selections from special crosses in terms of its ability to partition assimilate .
π SIMILAR VOLUMES
An experiment was conducted in Winnipeg, Manitoba, Canada to : (1) ascertain the efficiency of gridded mass selection ; (2) to determine if additional selection efficiency can be achieved through refinement of the gridded mass selection procedure ; and (3) to determine if the degree of homozygosity