EFFECT OF TEMPERATURE FACTOR ON THE DURATION OF INTERPHASE PERIODS OF MELON PLANTS

Abstract

One of the valuable traits of any variety is its degree of adaptability to stressful environmental factors. The purpose of the research is to determine the degree of influence of average daily temperatures on the duration of interphase periods of some melon varieties in the first half of growing season to assess their ecological plasticity under conditions of the foothill zone of the Crimea. The studies were conducted in 2016–2019 on the experimental fields of FSBSI “Research Institute of Agriculture of Crimea” (village of Ukromnoye, Simferopol suburbs). All the research studies were carried out according to the existing guidelines for melon crops breeding. Fifty-six melon samples varying in reaching maturity were the objects of the study. Soil – chernozem southern calcareous heavy loamy; its texture is clayey, structure – lumpy. Weather conditions during the years of research varied. The most favourable temperature regime for the melon growing was in 2019 (2269.6 °С); unfavourable – in 2016 (1738.0 °С); 2017 and 2018 occupied an intermediate position. It allowed obtaining objective results in assessing ecological plasticity of the studied varieties. Planting scheme – standard; feeding area – 1.0×1.5 m2 per one plant. The study was carried out in a collection nursery; four-fold replication. We compared melons of three groups of ripeness: early (I) – varieties mature in 55–75 days, mid-early (II) – ripen in 76–90 days, mid-late (III) – require 90 days until harvest. During the years of research, the duration of interphase periods varied from 18 to 59 days. An increase in the relative average daily air temperature by 1 °C reduced the phenophases duration on average by 1.02–4.43 days. The most pronounced changes were revealed in the third interphase period (seedlings – fruit formation beginning): the average value of the ecological variation corresponded to 27.5 %; maximum it was in the mid-late samples (25.3 %). We established a close negative correlation (from –0.72 to –0.99) between an increase in the relative average daily air temperature and duration of the phenophases of the first half of the melon plants growing season. Each genotype reacted individually to changes in external influences. The group of mid-late samples had the highest degree of variability. An increase in the relative average daily temperatures by 1 °C reduces the length of the interphase periods of plants of this group from 1.99 to 3.75 days. Among others, varieties ‘Idyllia’, ‘Gulnara’, ‘Ethiopka’ were the most stable.