Yield potential of soybean varieties and its fulfillment

Abstract

Purpose and objectives. To determine peculiarities of the fulfillment of the yield potential of modern soybean varieties in different soil and climatic zones of Ukraine.
 Materials and methods. Fourteen soybean varieties bred at PPI NAAS and included in the State Register of Plant Varieties Suitable for Dissemination in Ukraine were studied: Podiaka, Malvina, Estafeta, Sprytna, Baika, Krynytsia, Kobza, Pysanka, Perlyna, Melodiia, Rainduha, Krasunia, Rizdviana, and Sloboda. The soybean yields were evaluated in the competitive variety trial (CVT) of the Laboratory of Grain Legume Breeding. The experiments were carried out in four replicates. The record plot area was 25 m2 in accordance with the state variety trial methods. For comparison, we used data on the yields of the same varieties obtained during the qualifying examination for suitability for propagation (SVT) of the Ukrainian Institute of Plant Variety Examination (UIPVE). Data were statistically processed, as B.A. Dospekhov described [18], using STATISTICA 10 and Exel.
 Results and discussion. It was found that the most favorable conditions for growing soybean were in the Forest-Steppe, where the average yield amounted to 2.22 t/ha with fluctuations within 1.94–2.47 t/ha. In the Woodlands, the yield averaged 1.99 t/ha, varying 1.76 t/ha to 2.28 t/ha. The worst conditions were observed in the Steppe, where the average yield was 1.85 t/ha with fluctuations within 1.38–2.25 t/ha. The yield averaged 2.02 t/ha across the SVT zones with the maximum of 2.15 t/ ha and the minimum of 1.83 t/ha. The minimum fulfillment of the yield potential (FYP) in the CVT was 41.3% related to the average across the climatic zones of Ukraine. The maximum FYP in the CVT reached 95.6%. On average, there was a 67.8% fulfillment of the yield potential of the soybean varieties in the CVT. At the same time, the FYP was revealed to depend on the hydrothermal conditions of the test years. The lowest FYP in the CVT was recorded for variety Sloboda (41.3%), which was tested under the unfavorable weather conditions for soybean in 2017 and 2018, when the average yield of the CVT accessions was 0.84 t/ha and 0.50 t/ha, respectively. The average yield from Sloboda in the CVT was 0.85 t/ha, while the average yield in the SVT was 2.06 t/ha. The yield loss was 58.7%. The highest FYP in the SVT was recorded for varieties Krasunia (95.6%), Melodiia (91.4%), Raiduha (84.2%), and Rizdviana (79.5%). For these varieties, the differences in the yield between the CVT and SVT were significantly lower (4.4–20.5%). The relatively high yields from these varieties in the CVT is attributed to the favorable conditions in 2016, when the CVT yield reached the maximum over the study period (2009–2018); the average yield of the varieties amounted to 2.59 t/ha.
 Conclusions. The most favorable conditions for soybean cultivation were in the Forest-Steppe of Ukraine. The average yield in this zone was 2.22 t/ha with fluctuations within 1.94–2.47 t/ha. In the Woodlands, the average soybean yield was 1.99 t/ha, ranging 1.76 t/ha to 2.28 t/ha. In the Steppe, the average yield was 1.85 t/ha, with the minimum of 1.38 t/ha and the maximum of 2.25 t/ha. The yield across the SVT climatic zones averaged 2.02 t/ha, with the maximum of 2.15 t/ha and the minimum of 1.83 t/ha. The minimum FYP in the CVT was 41.3%; the minimum yield was 0.85 t/ha in the CVT and 1.83 t/ha in the SVT. The maximum FYP in the CVT reached 95.6%; the maximum yield amounted to 1.75 t/ha in the CVT and 2.15 t/ha in the SVT. The average FYP in the CVT was 67.8%; the average yield was 1.37 t/ha in the CVT and 2.02 t/ha in the SVT.
 The fulfillment of the yield potential was revealed to depend on the hydrothermal conditions of the test years. It was demonstrated that the high genetically determined yield potential of the soybean varieties was significantly offset by unstable hydrothermal conditions during the soybean growing period, causing considerable fluctuations in the yields. For a more objective analysis of the yield in the competitive trials of soybean varieties, it is necessary to take into account not only the absolute yields of promising accessions, but also the total yield of the crop in individual years of research.