Selection of highly adaptive source material of watermelon for selection for early ripening

In terms of watermelon selection, the issue of stability of obtaining high yields in the conditions of manifestation of abiotic stressors of the external environment is relevant. The purpose of this study was to select a highly adaptive source material of watermelon according to the duration of the growing season and its components for use in breeding for early ripening. 101 collection samples of watermelon from 9 countries of the world were analysed. The study was based on the following methods: general scientific, measurement and weight, calculation, statistical. The watermelon collection was divided into ripeness groups and the sample was ranked according to the “duration of the seedling-ripening period”. The study established the amplitude (Am) and range of variation (Lim) of the signs of the duration of the components of the growing season. Samples with the smallest individual interphase periods were selected for use in selection for early ripening. The study found Vi – general adaptive capacity (GAC), σ2 SACi – specific adaptive capacity (SAC), Sgi – genotype stability, bi – regression coefficient of genotype response to changing conditions (plasticity), SVGi – selection value of the watermelon collection genotype based on the “duration of the growing season period”. According to the general adaptive capacity, the samples with the shortest duration of the “seedling – ripening” period were selected – 19 samples (Vi =-11.72…-6.05). As the most stable genotypes according to the “duration of the growing season” characteristic, 32 collection samples with a low value of the specific adaptive capacity indicator were selected, 23 of which are early ripening. The high stability of the genotype (Sgi) according to the characteristic “duration of the seedling-ripening period” was determined in 31 collection samples, of which 24 were early ripening. Based on the results of determining the regression coefficient (ecological plasticity coefficient), according to the characteristic “duration of the growing season”, the collection samples of watermelon were divided into three groups – with low (bi =0.01-2.20), medium (bi =2.21-4.22), and high (bi =4.23-6.24) ecological plasticity. According to the selection value of the genotype according to the trait “duration of the seedling-ripening period”, 18 collection samples had high indicators (SVGi =110.22-119.92), which are valuable for use in selection work with watermelon as sources of the characteristic “early ripeness”