Grain size in wheat is the most stable yield component and has a favorable effect on flour yield. To identify the chromosomes associated with the large grains of line G603-86, (grain weight over 60 mg and grain length of about 9 mm), F3 lines, extracted from F2 populations obtained from Fl monosomics of crosses between G603-86 (P1) and the monosomic set of Favorit (P2) were tested in the field. ANOVA showed significant differences among parents for grain weight and grain length, but not for grain width or the factor expressing the difference in grain form and density. Homoeologous groups had significant effects on grain weight and on all components of grain weight, while genomes were not significantly different for any of these characters. Grain weight was significantly increased by chromosomes 6D and 4A of G603-86. Grain length was significantly increased by chromosomes 4A, 4B, 2B, 3A and 1B, grain width by chromosomes 1A and 1B, and the factor form-density by chromosomes 6D and 6A. The high grain size in G603-86 results from the effects of genes located on many chromosomes which affect grain dimensions, form and density.
Understanding the relationship between grain filling (GF) characteristics, earliness, and N accumulation would aid in improving grain size and grain protein content in wheat (Triticum aestivum L.). significant association of early anthesis, long GF duration, low GF rate, and high protein concentration was found in a set of F1 hybrids and their parents from a 4 × 4 diallel cross involving Chinese and U.S. cultivars. This association was also found in an F2 population of a cross between an early hard red winter Chinese wheat and a late soft white winter U.S. cultivar. Expressing GF duration and rate on a temperature basis (degree days) removed the correlation between anthesis date and GF parameters and showed that the early parent with a longer GF duration in days actually required less degree days for GF than did the late‐heading parent. Regardless of the way of expressing GF parameters, a significant negative correlation was found between rate and duration of GF, suggesting a physiological barrier in combining high values for both traits. Kernel weight was significantly correlated with GF rate but not with GF duration, opening the possibility of breeding early maturing cnitivars with reduced GF period without sacrificing grain weight. Grain protein concentration was negatively correlated with GF rate and positively correlated with GF duration, regardless if GF parameters were expressed on a time or temperature basis. These results suggest that improvements in both grain size and grain protein concentration will be difficult but not impossible and that selecting for long GF duration might be beneficial in this respect. Expressing GF parameters on a temperature basis proved useful in removing the differential influence of temperature variation on plants of different earliness.
Rye has already proven to be a good donor of genes for improving important traits and diversity in wheat breeding. The agronomic advantages of wheat-rye translocations, as well as their detrimental pleiotropic effects, were shown to be dependent on the source of the transferred rye chromatin. This justifies continued effort for introgression of rye genes from various sources into various wheat backgrounds. There are still many genes of interest for wheat improvement, not yet transferred, that are available in the rye genome. This paper describes the strategy applied at the National Agricultural Research and Development Institute Fundulea (Romania), to take advantage of the existence of intensive breeding programs in both winter wheat and triticale, and presents some of the results obtained so far by applying this strategy, in obtaining lines with common bunt, barley yellow dwarf (BYDV) and other diseases resistances, as well as improved seedling vigour and crop spectral reflectance.
Early detection of genotypic differences in response to water stress would help in increasing selection intensity in breeding drought tolerant wheat (Triticum aestivum L.). However, detection of small differences requires adequate control of the stress level. A system was used to determine if differences among genotypes in growth response to water stress could be detected. Haun stage and shoot dry weight were determined after 20 d in 25 cultivars grown with adequate water supply or with a water deficit imposed by lowering the water table by 8 cm and by interposing a porous ceramic disk, with an air exclusion value of 0.5 MPa, in the conducting medium between the water table and the roots. Significant differences were found among cultivars in the response to the imposed water deficit. Hann stage reduction varied between 13% in the spring wheat ‘Klasic’ and 36% in ‘Apollo’, while shoot dry weight reduction was between 21% in Klasic and 67% in the club wheat ‘Moro’. The coefficient of correlation between the Haun stage and shoot dry weight response to water stress was highly significant (r = 0.78). Although no direct comparison could be made between response of early growth to water deficits and yield response in the field under drought stress, the results of the seedling growth test corresponded well with previous knowledge about the performance of the tested cultivars under water stress. Our results verified that the system could be useful for rapid evaluation of drought response in wheat breeding.
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