Influence of heat and moisture supply on the manifestation of breeding-valuable quantitative traits of courgette lines

Abstract

Abstract. Breeding work was carried out with 20 lines of courgette of foreign origin. The correlation was determined between the hydrothermal coefficient (HTC) and traits that are structural components of yield and determine the phenological phases of plant development. 3 perspective lines were obtained, in which there was a medium-strength correlation between GTC and the duration of the fruiting period (r_p = 0.37… 0.45). A group of lines        (3 samples) was selected, in which the average and moderate correlation with HTC  (r_p = 0.3… 0.70) was observed in terms of plant yield and productivity. One line (LK-17-11) was singled out, which had weak correlations with HTC on three important quantitative traits –  “Total yield”, “Commodity yield”, “Total productivity of one plant” (r_p = 0.12… 0,14).

Keywords: courgette, line, hydrothermal coefficient, correlation, quantitative traits.

Introduction. Due to global climate change, the topical issue of courgette breeding is the creation of varieties and hybrids of F₁ with maximum adaptability to soil and climatic conditions of cultivation.

Analysis of recent researches and publications. Existing varieties of courgette of Ukrainian breeding mainly belong to the intensive type of cultivation and largely depend on favorable local soil and climatic conditions of cultivation, which is not always achieved in modern climate change towards increased heat, drought and reduced rainfall. In recent years, breeding research at the Institute of Vegetable and Melon NAAS was aimed at creating a valuable breeding material of courgette with a combination of high adaptive potential to stress factors of cultivation and stability of signs of productivity and early maturity.

Purpose. The goal is to investigate the correlation between the level of manifestation of quantitative traits and the hydrothermal coefficient (HTC) in selectively valuable courgette lines and to identify promising forms with a low dependence on climatic growing conditions.

Methods. Breeding’s work was carried out with 20 lines of courgette of different geographical origin. Breeding studies on courgette were conducted in the field condition during 2017–2019 on the experimental basis of the Institute of Vegetable and Melon NAAS, located in the Left Bank Forest-Steppe of Ukraine. The correlation relationship was determined between the HTC and traits that are structural components of yield and determine the phenological phases of plant development.

Results. In general, the dynamics of meteorological conditions at the level of long-term averages over the years of research corresponded to the eastern part of the Forest-Steppe of Ukraine in terms of biological optimum for courgette plants. But the meteorological conditions of the years of research differed significantly in temperature and moisture regime as a whole during the growing season and in some phases of development of courgette plants. This made it possible to obtain objective data on the identification of lines that had increased resistance to lower moisture levels and higher daily temperatures during the vegetative phase of development.

It was found that most lines had strong (r_p = 0.7… 0.90) or very strong                           (r_p = 0.9… 0.99) correlations between HTC and the duration of phenological phases of plant development, which determine the periods from mass shoots to the mass flowering of female, male flowers and the first collection. Analysis of the influence of weather conditions on the fruiting period showed greater differentiation of linear samples according to the level of correlation between HTC and the duration of this phenological phase of development. There were 3 lines in which this connection took place of medium strength – LK 17-11, RVL-19, VL-91 (r_p = 0.37… 0.45).

There were 8 lines (LC 17-1, LC 17-2, LC 17-8, LC 17-50, RVL-19, VL-91, VL-92, Vedi) mainly with intensive type of cultivation, in which there were strong or very strong correlations between the level of HTC (r_p < 0.7… 0.99) and the manifestation of four quantitative characteristics (total and marketable yield, total productivity of one plant, average weight of marketable fruit). According to its reaction to the growing conditions to the same group should be attributed to the standard variety Chaklun.

A group of lines (LC 17-42, LC 17-44, LC 17-47) was selected, in which the average and moderate correlation with HTC (r_p = 0.3… 0.70) was observed in terms of general and commodity yield and plant productivity (r_p = 0.3… 0.70) . Among the linear samples, one stood out, LK-17-11, which had weak correlations with SCC on three important quantitative characteristics – “Total yield”, “Commodity yield”, "Total productivity of one plant" (rp = 0.12… 0.14).

Discussion. The obtained data on the correlation between HTC and breeding-valuable quantitative traits are a valuable source of information in terms of forecasting the manifestation of valuable breeding traits in breeding courgette lines, among which are such important as “Total yield” and “Fruiting period”. The obtained data will significantly simplify the breeding of source material for ecological breeding of courgette.