Genotype-specific response of winter wheat (Triticum aestivum L.) to irrigation and inoculation with ACC deaminase bacteria

Drought stress is a major factor limiting wheat production in rain-fed areas around the world. Wheat tolerance to drought stress may be enhanced through genotypic selection, but recently, there has been interest in manipulating wheat-microbial interactions to promote drought tolerance. The prime objective of the study was to examine the effects of inoculation with 1-aminocyclopropane-1-carboxylic acid (ACC)-deaminase containing (ACC+) bacteria on different winter wheat genotypes (grown in 1 m tall × 10 cm diameter tubes) under water-stressed and well-watered conditions as determined by root length, above- and below-ground biomass, and leaf relative water content. The results of the present study revealed that under water stress, inoculation with ACC+ bacteria increased leaf relative water content (RWC) for genotypes RonL and OK06318 by 22%, compared with non-inoculated controls. Under water stress, length of roots with a diameter class of 0.75-1 mm increased by 129% in response to ACC+ bacteria in the deepest tube section (67-99 cm depth increment). Under well-watered conditions, inoculation increased above-ground biomass for RonL and TAM112 by 37% and 32%, respectively, as compared to non-inoculated controls. Inoculation also increased RonL root biomass by 150% in the deepest tube section, and increased the length of roots with a diameter class of 0.50-0.75 mm in the deepest tube section for TAM112 by 40%. The results further showed that, irrespective of irrigation regime, the genotype RonL appears to be a good plant model to study wheat interactions with ACC+ bacteria. Collectively, the results of the present study revealed that the growth response of winter wheat to inoculation with ACC+ bacteria was genotype dependent. The variation among wheat genotypes in their response to ACC+ bacteria might lead to innovative selection strategies for improved water stress tolerance.