Relationships between canopy assimilation surface capacity traits and grain productivity of winter wheat genotypes under drought stress

Aim. A comparative analysis of several traits of the capacity of the assimilation apparatus of 10 varieties and 2 lines of winter wheat from Ukraine, under conditions of insuffi cient precipitation and elevated air temperature during the period, when the reproductive organs formed (GS 30–49), in order to search for phenotypic markers associated with high productivity. Methods. Field, morphometric, spectrophotometric and statistical methods were used. Results. The maximum difference in yield between varieties and lines, which grew under condi- tions of insuffi cient water supply and high temperatures in April and May of growing season 2017/2018, was 24.7 %. Under these conditions, the highest grain productivity was observed for the new varieties Pochayna, Hospodarka and Kyivska 17 (8.60–8.73 t/ha) and a high canopy leaves chlorophyll index at late stages of ontogenesis (0.38-0.48 g chlorophyll/m 2 at milky-wax ripeness). This was opposed to varieties Smuhlianka, Poradnytsia and the line UK 392/15 with the lowest yield (7.00–7.25 t/ha) and assimilation surface at this stage (0.07–0.17 g chlorophyll/m 2 ). At the fl owering stage (anthesis) the most productive varieties exceeded the least productive ones, on average, by 30 % in leaves fresh weight of the canopy, by 24 % in content of total (a+b) chlorophyll and by 60 % in canopy chlorophyll index. At milky-wax ripeness, the differences between these varieties increased signifi cantly – up to 136 % in leaf fresh weight of canopy, 57 % in chlorophyll content and 350 % in canopy leaves chlorophyll index. A close positive correlation (r = 0.69–0.77, P ˂ 0.01) between the canopy photosynthetic apparatus traits at milky-wax ripeness with the yield of varieties and lines of winter wheat under drought and high temperature stress was found. Conclusions. The results show that the leaves fresh weight of canopy and canopy leaves chlorophyll index can be used as markers of grain productivity of winter wheat under drought stress, as well as for the possible development of molecular genetic criteria of breeding, based on these phenotypic characteristics.