Drought tolerance induction and growth promotion by indole acetic acid producing Pseudomonas aeruginosa in Vigna radiata

Abstract

Drought accompanied with reduced precipitation is one of the key manacles to global agricultural throughput and is expected to escalate further hence posing major challenges to future food safety. For a sustainable agricultural environment, drought resistant plant growth promoting rhizobacteria (PGPR) are new encouraging prospect, which are inexpensive and have no side effects, as those of synthetic fertilizers. In the present study, five strains of Pseudomonas aeruginosa, the strain MK513745, strain MK513746, strain MK513747, strain MK513748, and strain MK513749 were used as drought tolerant PGPR with multiple traits of IAA production, N fixation, P solubilization, siderophore producing capabilities. The strain MK513745 and strain MK513749 produced higher quantities of indole acetic acid (116±0.13 and 108±0.26 μg ml-1). MK513749 yielded 12 different indole compounds in GCMS analysis. The strain MK513748 yielded maximum S.I. (3.33mm) for phosphate solubilizing test. Maximum nitrogen concentration was produced (0.18 μg ml-1) by strain MK513746. Percent siderophore units ranged from 2.65% to 2.83% as all five pseudomonas strains were siderophore positive. In all growth experiments of plant microbe interaction two varieties of Vigna radiata (AZRI-06, NM-11) plants inoculated with P. aeruginosa strains under drought stress responded significantly (P<0.05) better than control stressed plants. Maximum shoot length was enhanced up-to 125%, pod/plant 172%, number of grains 65%, 100 seed weight 95%, 100 seed straw weight 124% and total yield 293% were recorded in plants inoculated with drought stress tolerant PGPR in both varieties as compared to respective stressed control plants. Photosynthetic activity, membrane stability (45%), water content (68%) and antioxidant efficacy (19%) were improved with PGPR inoculations. The variety NM-11 (V2) was more tolerant to drought stress with inoculations of Pseudomonas strains than AZRI-06 (V1). Inoculations with these indole acetic acid producing strains would be suitable for plant growth promotion in areas facing water deficiency.

Fig 1

(a) Electrogram of MK-513749 auxin metabolites showing abundant peak (9.475 min); fragmentation of daughter ions in to (b) indolizine; (c) 2-methyle benzonitrile; (d) indole ring; (d) pyrin dine in GCMS analysis.

Fig 2

Effect of PGPR on the root length (a); shoot length (b); root fresh weight (c); shoot fresh weight (d) and plant dry biomass (e) of two different varieties of Vigna radiata grown under different drought conditions in lab trials. (t1 = 10% PEG and t2 = 20% PEG). The figure indicated traits varied significantly as a function of varieties (P<0.05), PEG (P<0.01) and strains (P<0.01).

Fig 3. Biplot of PCA (principal component analysis) expressing different levels and relationship between enzyme productions, growth and yield parameter induction by drought tolerant strains in both varieties of Vigna radiata under water stress conditions.

V1-AZRI 2006; V2-NM 2011.