Improved water productivity in summer squash under water deficit with PGPR and synthetic methyl amine applications

Abstract Insufficient freshwater resources require the improvement of deficit irrigation with approaches that induced high yields by increasing the adaptation of plants to physiological and photosynthetic responses to water scarcity in the soil. The aim of this study is to evaluate water productivity applying combinations of three different plant growth promoting rhizobacteria-PGPR (Bacillus megaterium TV91C, Bacillus megaterium TV6D, Bacillus subtilis RK1900) with a synthetic methylamine molecule for summer squash (Cucurbita pepo L.) at four irrigation levels (full irrigation, and 15, 30 and 45% deficit irrigation), comparing with control (without PGPR and MA). For that, the results of the small plot field experiment carried out in squash growing season of 2017 and 2018 in a semi-arid region were evaluated. PGPR + MA applications decreased the harmful effects on photosynthetic traits (Pn, gs, Ci and Tr), chlorophyll content, electrolyte leakage and leaf relative water content by water deficit and significantly improved also. Although the negative correlations between yield and physiological and photosynthetic traits, PGPR + MA applications provided higher marketable yield as much as the plants full irrigated even at low irrigation levels with a potential root growth from physiological and photosynthetic improving. Higher yield in PGPR + MA applications resulted in higher water productivity for water consumption and decreased irrigation quantities also increased water productivity for irrigation quantity applied. The most striking result was that all PGPR + MA applications resulted in significantly higher water consumption and water productivity for irrigation quantity applied values at all irrigation levels compared to the fully irrigated control treatment. Therefore, it would be possible to optimize water productivity, with water saving and squash yield increases from PGPR + MA applications in terms irrigation water management.