ENGLISH VERSION

ZESZYT 367

Barbara Skwaryło-Bednarz
The effects of environment and cultivar factors on quantity and quality of yield of seeds of winter oilseed rape that is cultivated in Lower Silesia 
zeszyt 367, ss. 100

Modern winter oilseed rape breeding makes it possible to obtain cultivars with specific quality parameters. The quality of rape seeds for food, fodder, and non-food purposes is continuously being improved by increasing the contents of oil, biologically active compounds (such as tocopherols) changes in composition and proportion of fatty acids and further reduction of anti-nutrition compounds in seeds. The previous studies on the influence of selected environmental and cultivar factors on quality of winter oilseed rape seeds mainly concentrated on the profile of fatty acids. Occasionally, attempts were made to determine the contents of tocopherols and plastochromanol-8 in winter oilseed rape seeds. For this reason, it was also necessary to determine the genotype-environment reaction of winter oilseed rape cultivars on the content of the most significant antioxidant compounds that could be found in rape seeds.

The aim of the study was to investigate the influence of environmental and cultivar factors on: winter oilseed rape yield, level of glucosinolates, accumulation of fat, fatty acids profile and content of tocopherols and plastochromanol-8.

The investigated material was obtained from experiments carried out in Post-Registration Variety Testing System (PDO testing system) in Lower Silesia in the years 2007/2008–2009/2010. Three open pollinated cultivars: Castille, Casoar, Cadeli and three hybrid cultivars: Extend F1, Nelson F1, Toccata F1 were selected for the experiment. The cultivars were cultivated in 6 locations – environments: Krościna Mała, Naroczyce, Pawłowice, Tarnów, Tomaszów Bolesławiecki, and Zybiszów. All the experiments were started in four repetitions with random blocks method. The area of the plot in each experiment was 12 m2. Similar cultivation and nurture methods were used for each experiment, according to the methods used by the Research Centre for Cultivar Testing

(COBORU). The following chemical analysis were made on winter oilseed rape seeds: content of glucosinolates (with silyl derivatives desulphoglucosinolates gas chromatography method), content of fat (with fat-free residue method in Soxhlet’s apparatus), profile of fatty acids (with fatty acids methyl esters gas chromatography method (FAME)), and contents of homological tocopherols and plastochromanol-8 (with highly-efficient liquid chromatography method).

The results have proved that the weather conditions in the experimental years significantly influenced winter oilseed rape yield, efficiency of fat and chemical composition of seeds. An even distribution of precipitation in spring-summer vegetation period significantly influenced the amount of winter oilseed rape yield. The largest yield and fat efficiency were obtained in the second year of the experiment which had the most favorable precipitation and temperature distribution in spring-summer vegetation period. The large sum of precipitation and moderate temperatures in the third year of the experiment favoured accumulation of fat in seeds. Weather conditions slightly influenced the content of glucosinolates in seeds, and the smallest sum of precipitation during spring vegetation period favored their accumulation in the first year of the experiment. Moreover, hydro-thermal conditions in the experimental years influenced the content of antioxidants – alpha-tocopherol had the largest biological activity, and gamma-tocopherol and plastochromanol-8 with strong antioxidant properties that positively influenced the oxidative stability of oils. The hydro-thermal conditions in the years of the experiment also influenced the sum of tocopherols and proportion of alpha-tocopherol to gamma-tocopherol in rape seeds.

Rape has high soil requirements and, in effect, produces different yield in diverse environments. In author’s studies the yield of rape largely depended on quality of soils where the experiments were carried out. Environmental factor significantly influenced the amount of yield, content and efficiency of fat, and to a small extent the content of glucosinolates. Moreover, a significant influence of environmental conditions was observed on fatty acids profile in oil, the content of the most important homologs of tocopherols – alpha-tocopherol and gamma-tocopherol in seeds and the sum of tocopherols in seeds. Long-term studies confirm that hybrid cultivars yield about 10–20% better than open pollinated cultivars. The synthesis of author’s three-years experiments revealed that the highest yield of seeds was observed in hybrid cultivar Nelson F1, whereas the lowest yield was observed in open pollinated cultivar Castille. Moreover, genetic factor significantly influences the content and efficiency of fat and level of glucosinolates. Also, genetic factor strongly determined the quality of fat and fatty acids profile. Hybrid cultivar Nelson F1 had the highest content of polyunsaturated fatty acids and unsaturated acids 18-C. Apart from the composition of fatty acids in oil, their right proportion plays an important role in human diet. The ratio of linolic acid to linolenic acid should be narrow – 2–3:1. The largest ratio of linolic acid to linolenic acid was observed in hybrid cultivars – Nelson F1 (2,18:1) i Toccata F1 (2,10:1). Moreover, the seeds of Nelson F1 had the highest content of antioxidants – alpha-tocopherol, gamma-tocopherol and total tocopherols.

A environment-genotype interaction was observed in relation to majority of the investigated features influencing the quality of seeds of winter oilseed rape. For this reason, genetic factor should be taken in consideration in cultivation of winter oilseed rape. Genetic factor is one of the most important elements of agritechnique that determines the quality of yield and plays an important role in the amount of accumulated compounds that act as antioxidants in seeds, especially alpha-tocopherol that shows the largest biological activity. These compounds may be important for preventing civilization diseases. Also, the hydro-thermal conditions significantly influence the amount of synthesized gamma-tocopherol and plastochromanol-8 which effectively protect polyene fatty acids from oxidation. A thorough knowledge of the ways that environment and genetic factors influence the amount of natural bioactive substances in the seeds of two types of winter rape that are cultivated in the Silesia region will make the future choice of the cultivar with the largest content of these substances easier.