THE ROLE OF AGRO-ECOLOGICAL CONDITIONS IN THE REALIZATION OF GENETIC POTENTIAL PRODUCTIVITY IN WINTER WHEAT (TRITICUM AESTIVUM L.) VARIETIES

Abstract

In Ukraine, winter wheat (TRITICUM AESTIVUM L.)  is the main food grain crop. From the sources available, it is known that grain croppage is not stable in terms of time and space. Even in the most favourable for wheat 2008 and 2015 years, the average yield over the country reached only 34.0 and 38.0 metric centners per hectare, respectively. The problem of rising croppage and obtaining high-quality grain may be solved in two approaches. The first approach is breeding. Breeders had already created varieties of intensive type, which yield potential can reach 10 tons. However, as a matter of fact, rising productivity in the process of breeding goes along with partial loss of adaptive capacity resulting in lack of stability of a variety.

 Another approach to the issue of increasing grain croppage is creating such optimal conditions for plant growth and development, which make it possible to prove the genetic potential of a variety, to obtain high yield along with maximum resistance to adverse environment. We investigated the efficacy of mineral fertilizers in the realization of genetic yield potential of 12 winter wheat (TRITICUM AESTIVUM L.) varieties of Bila Tserkva breeding.

Materials and methods.  During the 2012- 2015 period , in the years contrasting in terms of meteorological indicators, against basic fertilizer background we studied the effect of fertilizer, its application rate and number of applications in the main stages of organogenesis in sowings of wheat varieties characterized by different morphological and biological characters and different level of genetic adaptation to stressful environmental conditions. In terms of ripening, the varieties represent the following groups: (i) early maturing: Bilotserkivska Napivkarlykova; (ii) mid-early: Olesia, Lisova Pisnia, Tsarivna, Romantyka and Shchedra Nyva; (iii) mid-ripening Perlyna Lisostepu, Elehiia, Yasochka, Lybid, Vidrada and Charodiika Bilotserkivska. It terms of height, Bilotserkivska Napivkarlykova is semi-dwarf, varieties Olesia and Shchedra Nyva are dwarf, all the others are medium-height varieties [1]. All varieties feature either good or excellent baking quality. Among them, Bilotserkivska Napivkarlykova (as a semi-dwarf variety) and Perlyna Lisostepu (as a mid-ripening one) have been approved the national standard varieties for Polissia and Forest-Steppe of Ukraine for seven years. Another variety, Lisova Pisnia has been approved the national standard variety for the same zone since 2014.

The experiment was arranged in plots with accounting area of 50 m² with four-time replication. In autumn (after vegetation ceased), in spring (after vegetation started) and in the stage of leaf-tube formation through all the years of the experiment and in all the treatments, we determined following indicators: total and productive tillering, weight of 100 plants, level of expression of the main diseases, resistance to lodging (in the late stage of milky-wax ripeness) and yield structure.  In addition, we recorded morphological features, such as plant height, angle between stem and flag leaf and availability of waxy coating.

The experiment was arranged according to the three-factor plan: factor A- variety , factor B – fertilization  and factor C- year . Analysis of weather conditions during the 2013-2015 period showed that they were enormously contrasting.

Against the background of basic compound NPK fertilizer (N₃₂P₃₂K₃₂) appliedat the rate of 2 centners per hectare we studied additional fertilizing as follows: treatment 2, in the stage of spring tillering; treatment 3, in the stage of spring tillering + in the flag leaf stage; treatment 4, basic fertilization only.

Results. Presented in the Tables 2 , 3, 4  data illustrate response of twelve wheat varieties on fertilization in the experiments 2013, 2014 and 2015 years. In the control treatment (without fertilizers), yield was the lowest in the experiment. Meanwhile, relatively high yield was obtained in drought-resistant varieties (Olesia, Bilotserkivska Napivkarlykova and Yasochka). The smallest effect was observed in treatment 4 (+ 2.5 centner/ha). At the same time, mid-early, similar in their genotype varieties Tsarivna, Lisova Pisnia and Romantyka reacted positively on basic fertilization. In treatment 2 with the minimum fertilizer application rate in the stage of tillering, yield increased (on the average of varieties) of 3 centner/ha, in particular, the highest fertilizers efficacy reflected middle-ripening varieties (Charodiika Bilotserkivska and Perlyna Lisostepu).

In treatment 3, where additional fertilizing was carried out three times against the background of basic fertilizer, the best response in yield showed such varieties as Bilotserkivska Napivkarlykova, Olesia, Yasochka, Lisova Pisnia and Romantyka. Thus, application of N₁₇₃ in 3-8 stages of organogenesis in wheat revealed its potential yield as well as good response to fertilization in each variety under study under severe drought.

Weather conditions of 2014 were opposite to those of 2013. Winter was warm; spring start of vegetation was early (early March); the spring was rainy. Plants felt excessive moisture during all stages of organogenesis. The limiting factors for yield potential in 2014 were strong and early lodging, exosmosis, development of septoria leaf spot and fusarial head. Average yield of all varieties was the highest in the treatment without fertilization. Perlyna Lisostepu, Charodiika Bilotserkivska and Bilotserkivska Napivkarlykova were the least affected by lodging and exosmosis. Vidrada and Olesia logged earlier than other varieties; they intensively tillered and showed the greatest value of 100 plants weight in the phase of leaf-tube formation under the condition of elevated moisture since the autumn.

Conclusion. When applying fertilizers, it is important to consider morphological, biological and physiological characteristics of wheat varieties that will allow better meeting their needs for mineral nutrition, increasing the efficiency of the fertilizing and reducing yield losses caused by stressful environment.

Weather conditions in different years affect a variety response to timing and application rate of a fertilizer. This fact must be taken into account when planning agronomical practices in order to achieve maximum genetic productivity potential of a variety.

This study on plasticity and stability of wheat varieties against different mineral nutrient backgrounds under different for their weather conditions years will help to identify natural habitat of the varieties when introducing them into production.