Improvement of genomic prediction in advanced wheat breeding lines by including additive-by-additive epistasis

Key message Including additive and additive-by-additive epistasis in a NOIA parametrization did not yield orthogonal partitioning of genetic variances, nevertheless, it improved predictive ability in a leave-one-out cross-validation for wheat grain yield. Abstract Additive-by-additive epistasis is the principal non-additive genetic effect in inbred wheat lines and is potentially useful for developing cultivars based on total genetic merit; nevertheless, its practical benefits have been highly debated. In this article, we aimed to (i) evaluate the performance of models including additive and additive-by-additive epistatic effects for variance components (VC) estimation of grain yield in a wheat-breeding population, and (ii) to investigate whether including additive-by-additive epistasis in genomic prediction enhance wheat grain yield predictive ability (PA). In total, 2060 sixth-generation (F6) lines from Nordic Seed A/S breeding company were phenotyped in 21 year-location combinations in Denmark, and genotyped using a 15 K-Illumina-BeadChip. Three models were used to estimate VC and heritability at plot level: (i) “I-model” (baseline), (ii) “I + GA-model”, extending I-model with an additive genomic effect, and (iii) “I + GA + GAA-model”, extending I + GA-model with an additive-by-additive genomic effects. The I + GA-model and I + GA + GAA-model were based on the Natural and Orthogonal Interactions Approach (NOIA) parametrization. The I + GA + GAA-model failed to achieve orthogonal partition of genetic variances, as revealed by a change in estimated additive variance of I + GA-model when epistasis was included in the I + GA + GAA-model. The PA was studied using leave-one-line-out and leave-one-breeding-cycle-out cross-validations. The I + GA + GAA-model increased PA significantly (16.5%) compared to the I + GA-model in leave-one-line-out cross-validation. However, the improvement due to including epistasis was not observed in leave-one-breeding-cycle-out cross-validation. We conclude that epistatic models can be useful to enhance predictions of total genetic merit. However, even though we used the NOIA parameterization, the variance partition into orthogonal genetic effects was not possible.

Experimental Determination of the Influence of the Peeling Machine Constructive and Operating Parameters on the Criteria of the Peeling Process Efficiency

Introduction. The determination of the optimal technological efficiency of the peeling process, in terms of the number of detached casings and unit costs of the process, is an important task. The purpose of the study is to give reasons for a comprehensive evaluation criterion of the technological efficiency of peeling wheat grain and choose the optimal values of the parameters of grain peeling, taking into account the energy intensity of the process. Materials and Methods. To quantify the technological efficiency of peeling wheat grain, we used the following local efficiency criteria: the relative yield of peeling by-products, the relative decrease in grain ash content, the increase in the number of cracked grains, and a comprehensive criterion of efficiency taking into account local criteria and the specific power consumption. Results. The experiments have shown that the technological feasibility of the peeling process is ensured at the percentage of the flap opening at the outlet of the machine 60‒70%. In this case, the relative yield of waste husk is 3.2‒2.8%, the relative decrease in grain ash content is 0.32‒0.20%, and the increase in the number of cracked grains does not exceed 0.85%. With increasing the degree of the flap opening at the outlet of the machine from 50 to 100%, the specific power consumption decreases from 8.7 to 3.5 kW∙h/t. Discussion and Сonclusion. To assess the technological efficiency of wheat grain peeling a generalized efficiency criterion, which includes local criteria, is proposed. It has been experimentally proved their dependence on the intensity of grain processing in the machine. The optimum combination of the flap opening degree at the outlet of the machine at 67% (productivity 0.7 t/h) and the specific power consumption of 5.8 kW∙h/t was defined. In this case, the efficiency complex criterion, taking into account the process energy intensity of, is 4.5 kg/kW∙h.

AUGER CONVEYOR-DISTRIBUTER OF GRAIN

The construction of a solar dryer-grain storage facilities is described. The design of a auger conveyor-distributor of grain for its loading is offered. The dependence of the width of the discharge opening in the casing of the auger conveyor-distributor on its length is obtained. The results of laboratory tests of the auger conveyor-distributor of grain are presented. It is established that the minimum initial width of the drain opening for wheat grain should be not less than 9 mm. The conditions of uniform distribution of grain by the auger conveyor-distributor are justified: the filling factor of the auger interturn space in its loading zone – 0.35; the length of the discharge opening of the charging hopper should be equal to the doubled value of the auger pitch size. In this case, the uneven distribution of grain along the discharge opening will be no more than 5%.

Yield and grain quality of baking winter wheat of different varieties

Purpose. Study the formation of yield and grain quality of baking winter wheat of different varieties. Methods. Laboratory, physico-chemical, mathematical and statistical. Results. The grain yield of baking winter wheat varied significantly depending on the variety. On average over two years of research, the highest yield (8.12–8.47 t/ha) was obtained in ‘Colonia’, ‘RGT Reform’, ‘Quebec’, ‘Tobak’, ‘Mescal’ and ‘Emile’ varieties. In ‘Bonanza’ and ‘Rivero’ varieties, this indicator was at the level of 7.48–7.53 t/ha. It should be noted that the stability index was high (0.92–0.98) for growing all varieties. In the favourable 2020 year, the grain yield ranged between 7.62 and 8.80 t/ha, while in the less favourable years it ranged between 7.34 and 8.26 t/ha depending on the variety. On average, over two years of research, the protein content of more than 13.0% was formed by ‘Emile’, ‘Bonanza’, ‘RGT Reform’ and ‘Quebec’ varieties, while in other the varieties it was 12.4–12.9%. The studied varieties of baking wheat had a high stability of protein content (0.98–0.99). Baking winter wheat grain had an average gluten content of 27.7–29.7%, depending on the variety, with high stability. Its highest content (29.5–29.7%) was obtained in ‘Emile’, ‘Quebec’ and ‘RGT Reform’ varieties. The gluten content in grain was directly proportional to the protein content. There is a direct very high correlation between these indicators (r = 0.91 ± 0.001). According to the Zeleny sedimentation test results, flour strength was high only in ‘Quebec’ variety, while in the other varieties it was medium. The grain of ‘Quebec’ and ‘RGT Reform’ varieties corresponds to valuable wheat; ‘Rivero’ and ‘Bonanza’ correspond to a good filler, while the rest of the varieties correspond to a satisfactory filler. The grain of ‘Quebec’, ‘Mescal’, ‘Rivero’ and ‘Colonia’ varieties is medium hard as the hardness was 54.1–59.1 units of instrument. Grain of the other varieties is soft with 48.3–51.1 units of instrument. Grain of ‘RGT Reform’, ‘Rivero’, ‘Emile’ and ‘Tobak’ varieties had the largest (794–812 g/l) grain unit. This indicator in the other varieties was at the level of 760–785 g/l. Flour strength is directly proportional to protein content. There is the direct high correlation between these indicators (r = 0.87 ± 0.002). Correlation between the protein content and the sedimentation index by Zeleny test was direct high (r = 0.79 ± 0.001). However, with grain hardness it was inversely weak, and with the grain unit direct moderate (r = 0.35±0.003). Conclusions. Yield of winter baking wheat varieties was in the range from 7.48 to 8.47 t/ha, protein content varied from 12.4 to 13.8%. Protein content highly correlated with the major baking properties of wheat grain. Baking winter wheat ‘RGT Reform’ and ‘Quebec’ varieties are recommended for stable grain production with good baking properties in the conditions of the Right-Bank Forest-Steppe.