Grain yield of cereal crops depends to a large extent on attracting ability of spikes: the more intense it is, the more active is the out- and inf1ow and deposition of reserve substances in grain and the higher is the grain yield per unit area. Such ability of spikes depends on genotype, the growth and development stage, crop management practice and other internal and external factors. A research was carried out to detect those growth and development stages in which the greatest changes of some spike characteristics and total protein content are observed. The studies were carried out at the stages of milk, wax and full maturity, in two variants with optimum irrigation and without irrigation during the whole vegetation period. Four durum and two bread wheat varieties were evaluated. Spike grain weight, thousand grain weight and grain protein content were measured. The study provided evidence that grain formation during the ontogenetic stages proceeds differently in different experimental varieties. Varieties Mirbashir-50 and Guvvali-17 are characterized by higher spike grain weight than other varieties. Although the process of deposition of reserve substances in grain proceeds very fast during the first stages of grain formation, it slows down remarkably by the end of the wax stage. At the wax stage, as compared to that of the milk stage, the grain weight increased for Garagilchin-2 by 0.91 and 0.66g and for Sevinj -by 0.74, and 0.55g in the irrigated and mature stress variants, respectively. These varieties showed a higher increase in the grain weight as compared to other varieties. Garagilchin- 2, Vugar and Mirbashir-50 were found to be top yielders at the stage of full maturity in both variants. The difference in spike grain weight between the wax and full maturity stages made up for Garagilchin- 20. 72g and 0.22g, for Sevinj 0.63g and 0.21 g, and for Vugar 0.98g and 060g in the irrigated and mature stress variants, respectively. It was found that Vugar demonstrated higher increase in spike grain weight compared to other studied varieties. The highest increment in dry biomass accumulation in grain is observed at the wax stage, upon completion of which its intensity decreases. The highest increment in thousand grain weight was demonstrated by varieties Sevinj and Vugar. Noteworthy, that for these varieties the lowest values for the characteristic was recorded at the initial stages of grain formation. Slow growth of grain dry weight at the initial stage of spike formation leaded eventually to the highest values of thousand- grain weight and grain weight per spike at the end of plant development. The chemical composition of wheat grain also changes during the grain development, since the protein-starch ratio in wheat grain changes towards reduction of the protein share, determined through total nitrogen by Kjeldahl (Pleshkov, 1976). In Garagilchin-2, the total nitrogen content at the milk stage in the variant withoptimum irrigation was 2.95%, dropping to 2.44% by full maturity. Such decrease in Sevinj was found to be 0.41 %. Without . irrigation the total nitrogen content for Garagichig-2 and Sevinj were 3.00 and 3.09% respectively. Reduction in total nitrogen content from the milk to the wax maturity stages with and mature stress were found to be about 0.32 and 0.3% for Garagilchin-2, 0.38 and 0.32% for Sevinj, and 0.19 and 0.24% for Vugar, respectively. Between the wax and full maturity stages grain nitrogen content decreased by 0.17 and 0.18% for Garagilchin-2, by 0.03 and 0.03% for Sevinj, and by 0.27 and 0.27% for Vugar in irrigated and mature stress variants, respectively. Comparing total nitrogen content in the milk and full maturity stages, it can be concluded that the highest decrease of total nitrogen is ascertained for Garagi- Ichin-2-0.49 and 0.5%, Vugar-0.46 and 0.51%, and the lowest for Guvvali-17 -0.26 and 0.28%, in irrigated and non-irrigated variants, respectively. Deterioration of water supply was found to influence the protein-starch ratio in wheat grain towards increase of the total protein share as compared to the variant with the optimum irrigation. Thus, the analyzed data ascertains that wheat grain quality changes during the grain filling period and stabilizes only by completion of vegetation period. The quality characteristics are determined already at the beginning of the milk stage, although the ratio of nitrogen versus carbohydrates keeps altering to the completion of the stage of full maturity.

English

0407|AGRIS 0401|AL-Wheat Program

Juan Carlos Mendieta

CIMMYT Publications Collection