Modeling the Effectiveness of Bacillius subtilis Strains Depending on Natural and Climatic Factors in Soft Wheat Cultivation

Abstract

The studies were conducted to identify the natural and climatic factors that can influence the effectiveness (efficacy) of B. subtilis strains with respect to morphometric indicators and soft wheat productivity as well as development of the diseases in 2017–2022. A response of Leningradka 6, k‑64900 spring wheat to the microbiological formulation Vitaplan, SP (titer of viable cells ×10¹¹ CFU/g) and liquid culture (LC) of the B. subtilis strains VKM B‑2604D and B. subtilis VKM B‑2605D (at a 1 : 1 ratio with the titer of viable cells ×10¹⁰ CFU/mL). Wheat seeds were treated before sowing; the plants were subsequently sprayed three times during the growing season in the field conditions of the northwestern Russian Federation. The efficacy of bacterial strains in terms of the productivity and particularly harmful wheat diseases depended to a greater degree on the indicators of moisture availability during the growing season. This was confirmed by the results of multidimensional scaling as well the correlation and factor analyses of the indicators. The variant with Vitaplan, SP (DF, dry formulation) in F₁ demonstrated high positive factor loadings for the precipitation amount in June, July, and August; HTC in July; relative humidity in June (0.73–0.93); plant stage; plant height; area of flag and preflag leaves; and weight of a vegetative portion of the plant (0.71–0.80). Using the LC B. subtilis VKM V‑2604D + B. subtilis VKM B‑2605D, high positive factor loadings were identified for the precipitation amount in June and August; HTC in July and August (0.71–0.88); productive tillering potential; root weight; spike length; spikelet number per spike; number and weight of grains per spike; and the biological and potential yield (0.71–0.85). The B. subtilis strains’ application improved biological and potential yield by 32.5 ± 7.2% and 24.3 ± 7.0%, respectively, and reduced the intensity of diseases’ progression (by 11.7 ± 1.6% for root rot and by 7.6 ± 0.7% for powdery mildew) as well as brown and yellow rust. The efficacy of the bacterial strains, however, significantly depended on the climatic factors of the wheat growing season.