Drought stress can significantly reduce wheat growth and development as well as grain yield. This study investigated morpho-physiological and hormonal (abscisic (ABA) and salicylic (SA) acids) responses of six winter wheat varieties during stem elongation and anthesis stage as well grain yield-related traits were measured after harvest. To examine drought response, plants were exposed to moderate non-lethal drought stress by withholding watering for 45 and 65% of the volumetric soil moisture content (VSMC) for 14 days at separate experiments for each of those two growth stages. During the stem elongation phase, ABA was increased, confirming the stress status of plants, and SA showed a tendency to increase, suggesting their role as stress hormones in the regulation of stress response, such as the increase in the number of leaves and tillers in drought stress conditions, and further keeping turgor pressure and osmotic adjustment in leaves. At the anthesis stage, heavier drought stress resulted in ABA accumulation in flag leaves that generated an integrated response of maturation, where ABA was not positively correlated with any of investigated traits. After harvest, the variety Bubnjar, followed by Pepeljuga and Anđelka, did not significantly decrease the number of grains per ear and 1000 kernel weight (except Anđelka) in drought treatments, thus, declaring them more tolerant to drought. On the other hand, Rujana, Fifi, and particularly Silvija experienced the highest reduction in grain yield-related traits, considering them drought-sensitive varieties.

Winter wheat is susceptible to several diseases throughout the vegetative season whereas fungicide treatments are protection used to combat fungal pathogens and to improve plant growth thus mitigating grain yield reductions. One of the main diseases is Fusarium head blight (FHB) which can be a huge problem in wheat production. Twelve winter wheat varieties varying in FHB sensitivity were tested for control of FHB using fungicide treatments made in tillering or/and heading stage, with or without inoculation with Fusarium spp. to determine the grain yield response to fungicide application at different growth stages. The grain yield from fungicide treated plots was compared to non-treated plots in two seeding rates and Fusarium inoculated plots in two growing seasons (2019/2020 and 2020/2021). The average area under the disease progress curve (AUDPC) for Type I resistance was 109.48 in 2020 and 99.33 in 2021 year in VI treatment where fungicide application in heading and Fusarium inoculation simultaneously were performed. In VII treatment where only Fusarium inoculation was applied, AUDPC for Type I resistance in 2020 was 371.88 in average, while in 2021 that was 199.18 in average. Wheat varieties treated with a fungicide in the heading stage at the first year of investigation (2020) had higher grain yield, compared to non-treated plots or treated in tillering stage. These results indicated that application of fungicides in heading stage when there is sufficient moisture in May and June may increase chances of profitability from fungicide application at that growth stage. Cumulative rainfall from January till May, at year 2021 had a positive effect on the grain yield, when accumulated rainfall in this period increased chances of getting a higher yield response from fungicide application in the tillering stage. Fungicide applications should always be implemented in combination with sound agronomic management and FHB resistant varieties.

Improving wheat grain yield plays a significant role in ensuring global food security.Wheat production could be increased by the genetic improvement of wheat genotypes where delayed senescence with enhanced post-anthesis capacity and staygreen traits could have an important role. In this study, chlorophyll a fluorescence (ChlF) rise kinetics from the early until late senescence of flag leaves, grain yield and other agromorphological characteristics were compared for three winter wheat advanced lines under natural drought conditions. The differences between lines were observed when considering the heading date which was 1 and 4 days earlier for the line Osk.4.354/12-18, than lines Osk.4.312/10-18 and Osk.4.330/6-18, respectively. Furthermore, line Osk.4.354/12-18 had the highest test weight (kg hl À1 ), while line Osk.4.330/6-18 showed a tendency of decreased grain yield, compared to the other two lines. Analysis of ChlF transients and several JIP-test parameters indicated that all three lines had a generally similar course of changes in the photosynthetic performance of flag leaves during senescence under drought conditions. However, at the point when a decrease in photosynthetic performance was initiated, it was slightly less intensive in line Osk.4.354/12-18 accompanied by longer preservation of functionality and connectivity of PSII units, than in the other two lines, which contributed to its better agronomical performance. These results indicated that even delicate variations in the functioning of the photosynthetic apparatus of the flag leaf during grain filling were agronomically important, especially when plants were exposed to drought stress, and could be used to differentiate otherwise similar wheat genotypes. Even small genotype-specific differences in the photosynthetic performance of senescing flag leaves, along with earlier heading dates, could assist in the selection of genotypes with a better ability to cope with unfavourable environmental conditions.