ACC Deaminase Producing PGPR Bacillus amyloliquefaciens and Agrobacterium fabrum along with Biochar Improve Wheat Productivity under Drought Stress

Abstract

Drought stress retards wheat plant’s vegetative growth and physiological processes and results in low productivity. A stressed plant synthesizes ethylene which inhibits root elongation; however, the enzyme 1-Aminocyclopropane-1-Carboxylate (ACC) deaminase catabolizes ethylene produced under water stress. Therefore, the ACC deaminase producing plant growth promoting rhizobacteria (PGPR) can be used to enhance crop productivity under drought stress. Biochar (BC) is an organically active and potentially nutrient-rich amendment that, when applied to the soil, can increase pore volume, cation exchange capacity and nutrient retention and bioavailability. We conducted a field experiment to study the effect of drought tolerant, ACC deaminase producing PGPR (with and without timber waste BC) on plant growth and yield parameters under drought stress. Two PGPR strains, Agrobacterium fabrum or Bacillus amyloliquefaciens were applied individually and in combination with 30 Mg ha−1 BC under three levels of irrigation, i.e., recommended four irrigations (4I), three irrigations (3I) and two irrigations (2I). Combined application of B. amyloliquefaciens and 30 Mg ha−1 BC under 3I, significantly increased growth and yield traits of wheat: grain yield (36%), straw yield (50%), biological yield (40%). The same soil application under 2I resulted in greater increases in several of the growth and yield traits: grain yield (77%), straw yield (75%), above- and below-ground biomasses (77%), as compared to control; however, no significant increases in chlorophyll a, b or total, and photosynthetic rate and stomatal conductance in response to individual inoculation of a PGPR strain (without BC) were observed. Therefore, we suggest that the combined soil application of B. amyloliquefaciens and BC more effectively mitigates drought stress and improves wheat productivity as compared to any of the individual soil applications tested in this study.

Pongamia pinnata L. Leaves Biochar Increased Growth and Pigments Syntheses in Pisum sativum L. Exposed to Nutritional Stress

“…Similarly, in the current study, the chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and anthocyanin were significantly increased in response to a higher application rate of PLB (2%; Table 3). We did not find an exactly comparable study of same feedstock and crop; our findings can be compared to pot [75] and field [26] studies' findings. Moreover, a reduction (or antagonistic relation) of plant lycopene contents in response to PLB application also indicates the mitigation of the experimental nutritional stress in this study.…”

“…Increases in chlorophyll contents and yield attributes in responses to increasing timber-waste biochar in soil were also reported in a biochar trial on wheat crop under greenhouse [75] and laboratory [26] conditions. Similarly, in the current study, the chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and anthocyanin were significantly increased in response to a higher application rate of PLB (2%; Table 3).…”

“…Besides the potential improvements in plant-growth-friendly chemical and physical properties of soil (discussed above), biochar can enhance soil biological properties [70,72]. Biochar can contribute to better colonization of plant growth promoting bacteria (PGPR) [26]. The PGPR act as an allied factor for better availability of nutrients and contribute to increasing chlorophyll pigments in wheat plant [73].…”

Plant Growth Promoting Rhizobacterial Mitigation of Drought Stress in Crop Plants: Implications for Sustainable Agriculture

“…These strains can be used as inoculants for enhanced crop production, especially in arid environments. Some authors have also reported efficient utilization of ACC deaminase producing rhizobacteria in consortium with biochar [103,104], as well as in combination with plant growth regulators to enhance the yield of wheat plants under drought stress. Spraying of salicylic acid (SA) and putrescine (Put) at the rate of 150 mgL −1 on 25-day old chickpea seedlings in a consortium with PGPR resulted in significantly increased chlorophyll, protein, and sugar contents compared to the well-watered and drought conditions [105].…”

Rhizobacteriome: Promising Candidate for Conferring Drought Tolerance in Crops

“…PGPR possessing ACC deaminase activity reduce toxicity of heavy metals, drought stress and other abiotic stresses like extreme temperature, salinity and soil pH, besides, antagonism against phytopathogens 76 73 . Leclercia adecarboxylata and Agrobacterium fabrum, Bacillus amyloliquifaciens with higher ACC-deaminase and IAA production traits elevated nutrients uptake and high chlorophyll contents 78,79 . Pseudomonas fluorescens DR7 having high ACC deaminase-and EPS-producing ability increased moisture content in soil and enhanced the root adhering soil and root growth in foxtail millet 80 .…”