A synthesis-analysis of winter oilseed rape (Brassica napus L.) yield response to planting density under intensive cropping system

<p><strong>Background: </strong>Optimal yield is dependent on the collocations between plant population and individual growth. High plant populations for direct sown winter oilseed rape would be a prevailing way to achieve high yield under intensive cropping systems.</p><p><strong>Results: </strong>We investigated the oilseed rape yield response to planting density while considering the productivity environment, nitrogen (N) fertilizer, and sowing date. A synthesis-analysis was conducted by collecting the density-yield data in the field experiments of oilseed rape from 2000 to 2016 in China. The population yield response to different planting density levels could be described by a quadratic model, with threshold value of 45-60 plant m<sup>-2</sup>, and excessive density may cause yield loss as the weak individual growth. High planting density has no remarkable influence on the attainable population yield due to the decreasing individual potential yield. The population yield increment capacity by the increasing planting density was higher in medium yield environment (i.e., average yield at 1500-2500 kg ha<sup>-1</sup>). The planting density presented remarkably effect on population yield after the N limitation was relieved. Increasing planting density at 10<sup>4</sup> plants per hectare was equivalent to apply 1.17 kg N fertilizer on population yield, ranging from 0.42 kg to 4.76 kg under different yield environment levels. Yield loss caused by unsuitable sowing date (especially for the late sowing) could be compensated by increasing planting density.</p><p><strong>Conclusion: </strong>Planting density played a crucial role in cooperating the other management practices. Optimizing the allocation of plant population and individual growth, establishing target plant phenotype under high planting density would help to achieve high population yield.</p>

Variability of the «mass of seeds from a plant» sign in the soybeans hybrids of the different groups of ripeness

Aim. The purpose of the research is to determine the manifestation of the feature “seed weight from a plant” (the, parental forms) and hybrids, to establish the level of variability behind the soybean varieties in the F2–F5 hybrid combinations, to determine the effectiveness of selections for productivity in terms of the “seed weight from a plant” indicator from the hybrid populations of the F2–F5. Methods. The field, selection and genetic, calculation and comparative methods of the research were used. The varieties that are different in terms of fecundity and origin, also hybrids F1 and hybrid populations F2–F5 were studied. Selections on the basis of the “seed weight from a plant” were carried out in the F2–F5 populations. Results. It has been established that in soy characteristic “seed mass from a plant” has significant genotypic variability and has significant differences in varieties of different groups of ripeness, which may be a prerequisite for predicting the effective selection for this factorial trait. A high correlation of this trait with seed yield was also established. The proportion of the families from the selections, that were carried out in the F3 populations, exceeded the seed yield standard and was in the range of 28.0–37.5%. In the second generation of hybrids the efficiency of selection was 1.5–2 times lower. Conclusions. The highest yield of high-yielding genotypes, reached by the “seed mass from a plant” indicator was obtained from the F3 populations. To create the new high-yielding soybean varieties with a 3.5–5.5 t/ha yield under irrigation conditions, it is promising to use in the crossings the variety samples which are contrastive by groups of ripeness and genetic pedigree. Keywords: variety, soybean, hybrid, population, yield, irrigation.

NUTRITIONAL VALUE OF TWOYEARLING CARP OF DIFFERENT CROSS-BREEDS

One of the important fields of carp breeding work is improvement of the commercial traits of created carp breeds or cross-breed commercial crosses. The main indicator determining the value of commercial fish is edible carcass yield depending on the interior (relative weight of carcass edible parts) and the exterior (high spin, ratios of head and body girth, type of scale) indices. The paper presents the results of researches on interior indicators (body parts ratio) of twoyearlings of two-breed crosses obtained from crossing of adapted fourth generation imported breeds grown in Belarus with carp lines of Belarusian selection. The edible part of carcass size varied from 60.7 % (three prim x fresinet) to 66.7% (GermançLahvinsk scaly), averaging 64.0 % in the two-breed crosses studied. Compared with the average population yield of carcass in twobreed crosses, statistically significant advantages were determined in combinations of crossing with German carp. In this regard, quite high indicators were also observed in combinations with the Yugoslav carp, where it was used as the maternal component of crosses, and in combinations obtained from crossing the Mirror Isobelin carp with a Butterfly breed. Based on comprehensive assessment of interior indicators, a number of crosses have been determined with increased nutritional value of carcasses, among which the maximum nutritional value was shown by the cross Germançthree prim. The obtained data are of practical importance for creation of industrial hybrids with attractive commercial traits.