The stimulatory effects of plant growth promoting rhizobacteria and plant growth regulators on wheat physiology grown in sandy soil.

The present study was aimed to investigate the effects of plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) on the physiology and yield of wheat grown in less fertile sandy soil. The isolated PGPR strains were identified by 16S-rRNA gene sequencing as Planomicrobium chinense (P1), Bacillus cereus (P2) and Pseudomonas fluorescens (P3). Wheat varieties (Galaxy-13 and Pak-2013) differing in sensitivity to drought were soaked in fresh cultures of bacterial isolates and the PGRs (salicylic acid and putrescine) were sprayed at 150 mg/L on seedlings at three leaf stage. PGPR and PGRs treated plants showed significant increase in the contents of chlorophyll, sugar and protein even under harsh environmental conditions. Drought stress enhanced the production of proline, antioxidant enzymes and lipid peroxidation but a decrease was noted in the biochemical content (i.e. chlorophyll, protein and sugar) of inoculated plants. PGPR inoculation also significantly enhanced the yield parameters (i.e. plant height, spike length, grain yield and weight) and improved the fertility status of sandy soil. The accumulation of macronutrient, total NO3-N and P concentration and soil moisture content of rhizosphere soil was also enhanced by PGPRs inoculation. It is concluded that the combined effects of PGPR and PGRs have profound effects on the biochemical responses and drought tolerance of wheat grown in sandy soils.

A truncated FatB resulting from a single nucleotide insertion is responsible for reducing saturated fatty acids in maize seed oil.

KEY MESSAGE: We identified a G-nucleotide insertion in a maize FatB responsible for reducing saturated fatty acids through QTL mapping and map-based cloning and developed an allele-specific DNA marker for molecular breeding. Vegetable oils with reduced saturated fatty acids have signficant health benefits. SRS72NE, a Dow AgroSciences proprietory maize inbred line, was found to contain signficantly reduced levels of palmitic acid and total saturated fatty acids in seed oil when compared to other common inbreds. Using F2 and F3 populations derived from a cross between SRS72NE and a normal inbred SLN74, we have demonstrated that the reduced saturated fatty acid phenotype in SRS72NE is controlled by a single QTL on chromosome 9 that explains 79.1 % of palmitic acid and 79.6 % total saturated fatty acid variations. The QTL was mapped to an interval of 105 kb that contains one single gene, a type B fatty acyl-ACP thioesterase (ZmFatB; GRMZM5G829544). ZmFatB alleles from SRS72NE and common inbreds were cloned and sequenced. SRS72NE fatb allele contains a single nucleotide (G) insertion in the 6th exon, which creates a premature stop codon 22 base pairs down stream. As a result, ZmFatB protein from SRS72NE is predicted to contain eight altered and 90 deleted amino acids at its C-terminus. Because the affected region is part of the conserved acyl-ACP thioesterase catalytic domain, the truncated ZmFatB in SRS72NE is likely non-functional. We also show that fatb RNA level in SRS72NE is reduced by 4.4-fold when compared to the normal allele SNL74. A high throughput DNA assay capable of differentiating the normal and reduced saturate fatty acid alleles has been developed and can be used for accelerated molecular breeding.

Impacts of plant growth promoters and plant growth regulators on rainfed agriculture.

Demand for agricultural crop continues to escalate in response to increasing population and damage of prime cropland for cultivation. Research interest is diverted to utilize soils with marginal plant production. Moisture stress has negative impact on crop growth and productivity. The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGR) are vital for plant developmental process under moisture stress. The current study was carried out to investigate the effect of PGPR and PGRs (Salicylic acid and Putrescine) on the physiological activities of chickpea grown in sandy soil. The bacterial isolates were characterized based on biochemical characters including Gram-staining, P-solubilisation, antibacterial and antifungal activities and catalases and oxidases activities and were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN) and ammonia (NH3). The bacterial strains were identified as Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium based on the results of 16S-rRNA gene sequencing. Chickpea seeds of two varieties (Punjab Noor-2009 and 93127) differing in sensitivity to drought were soaked for 3 h before sowing in fresh grown cultures of isolates. Both the PGRs were applied (150 mg/L), as foliar spray on 20 days old seedlings of chickpea. Moisture stress significantly reduced the physiological parameters but the inoculation of PGPR and PGR treatment effectively ameliorated the adverse effects of moisture stress. The result showed that chickpea plants treated with PGPR and PGR significantly enhanced the chlorophyll, protein and sugar contents. Shoot and root fresh (81%) and dry weights (77%) were also enhanced significantly in the treated plants. Leaf proline content, lipid peroxidation and antioxidant enzymes (CAT, APOX, POD and SOD) were increased in reaction to drought stress but decreased due to PGPR. The plant height (61%), grain weight (41%), number of nodules (78%) and pod (88%), plant yield (76%), pod weight (53%) and total biomass (54%) were higher in PGPR and PGR treated chickpea plants grown in sandy soil. It is concluded from the present study that the integrative use of PGPR and PGRs is a promising method and eco-friendly strategy for increasing drought tolerance in crop plants.