Groundnut harbours non-nodulating non-rhizobial plant growth-promoting bacterial endophytes.

The present study was carried out to assess the growth-promoting ability of non-rhizobial endophytes in groundnut (Arachis hypogaea). Thirteen endophytic bacteria with different morphologies were isolated from the root and nodules of groundnut. These isolates significantly enhanced the growth of groundnut in sterilised vermiculite, though the isolates were unable to nodulate the host plant. The endophytic nature of these isolates was confirmed by their re-isolation from the sterilised and macerated roots of the plants. The isolates exhibited in vitro tricalcium phosphate and zinc solubilization, production of siderophores, auxins and ammonia as well as growth on different nitrogen-free media. The phosphate solubilization and auxin production varied from 50 to 196 and 17 to 71 µg/ml, respectively by the isolates. Based on phenotypic tests and 16S rRNA gene sequencing, four potential strains were identified as Klebsiella sp. R3, Pseudomonas putida R6, Klebsiella oxytoca GRE5 and Pseudomonas proteolytica GRE6. A significant increase in plant growth, chlorophyll content, nodule count and shoot nutrient content of groundnut was observed with these bacterial inoculations over the uninoculated control in greenhouse. The bacterial treatments resulted in increased N, P and K content in the shoot up to 87, 96 and 44%, respectively, over the control. Physico-chemical properties and available nutrient content of soil were also improved on bacterial inoculations. The results indicated that groundnut harbours beneficial non-rhizobial bacterial endophytes with the potential to be used as microbial inoculants in groundnut. Klebsiella oxytoca as a non-nodulating nodule endophyte of groundnut is reported for the first time.

Genome wide association studies for acid phosphatase activity at varying phosphorous levels in Brassica juncea L.

Acid phosphatases (Apases) are an important group of enzymes that hydrolyze soil and plant phosphoesters and anhydrides to release Pi (inorganic phosphate) for plant acquisition. Their activity is strongly correlated to the phosphorus use efficiency (PUE) of plants. Indian mustard (Brassica juncea L. Czern & Coss) is a major oilseed crop that also provides protein for the animal feed industry. It exhibits low PUE. Understanding the genetics of PUE and its component traits, especially Apase activity, will help to reduce Pi fertilizer application in the crop. In the present study, we evaluated 280 genotypes of the diversity fixed foundation set of Indian mustard for Apase activity in the root (RApase) and leaf (LApase) tissues at three- low (5µM), normal (250µM) and high (1mM) Pi levels in a hydroponic system. Substantial effects of genotype and Pi level were observed for Apase activity in both tissues of the evaluated lines. Low Pi stress induced higher mean RApase and LApase activities. However, mean LApase activity was relatively more than mean RApase at all three Pi levels. JM06016, IM70 and Kranti were identified as promising genotypes with higher LApase activity and increased R/S at low Pi. Genome-wide association study revealed 10 and 4 genomic regions associated with RApase and LApase, respectively. Annotation of genomic regions in the vicinity of peak associated SNPs allowed prediction of 15 candidates, including genes encoding different family members of the acid phosphatase such as PAP10 (purple acid phosphatase 10), PAP16, PNP (polynucleotide phosphorylase) and AT5G51260 (HAD superfamily gene, subfamily IIIB acid phosphatase) genes. Our studies provide an understanding of molecular mechanism of the Apase response of B. juncea at varying Pi levels. The identified SNPs and candidate genes will support marker-assisted breeding program for improving PUE in Indian mustard. This will redeem the crop with enhanced productivity under restricted Pi reserves and degrading agro-environments.

Performance of Dry-Seeded Rice Genotypes under Varied Soil Moisture Regimes and Foliar-Applied Hormones.

Plant hormones influence various physiological processes during the growth and development of plants, but their critical roles in influencing yield and antioxidant activities in dry-seeded rice (DSR) have not been adequately explored. This study aims to analyze the performance and antioxidant activity of contrasting genotypes of DSR in response to soil moisture regimes and foliar-applied hormones. The study comprised sixteen treatments that were evaluated under field conditions as per split-plot design in three replications. Treatments comprised combinations of two soil moisture tension regimes (10 kPa and 20 kPa) and two genotypes (PR-111, non-stay-green type and PR-123, stay-green type) applied to the main plots and foliar application of three hormones (gibberellic acid (GA3) 40 mg kg-1, abscisic acid (ABA) 20 mg kg-1, and cytokinin (CK) 40 mg kg-1)) and a control (unsprayed) to subplots. The non-stay-green genotype (PR-111) resulted in 34.6% more grain yield (6.48 t ha-1) than the stay-green genotype (PR-123) at the lower soil moisture tension regime (SMTR) (10 kPa) due to the increased number of filled grains per panicle and improvement in harvest index (HI). At the higher SMTR (20 kPa), the stay-green genotype (PR-123) produced 26.4% more grain yield (5.21 t ha-1) than non-stay green genotype (4.12 t ha-1) and showed enhanced superoxide dismutase (SOD) and peroxide dismutase (POD) activity that may have contributed in maintaining sink size through improved chlorophyll content. Grain yield (6.35 t ha-1) with foliar-applied GA3 (40 mg kg-1) at SMTR of 10 kPa was higher by 12.2% and 24.0% than with foliar-applied ABA (20 mg kg-1) and unsprayed treatments, respectively. Irrigation application at SMTR of 20 kPa and foliar application of ABA gave 24.1% higher grain yield (5.15 t ha-1) than the unsprayed treatment, but it was similar to foliar-applied GA3 and CK. This study implied that the stay-green genotype (PR-123) was more suitable under moisture stress conditions (20 kPa) in DSR, as it maintained sink size even under moisture stress conditions by improving dry matter translocation and enhancing SOD and POD activity. The study suggests the need to find out the endogenous level of these plant hormones in rice genotypes under a range of water regimes to develop high yielding and water use efficient genotypes of DSR.

Evaluating morpho-physiological and quality traits to compliment seed yield under changing climatic conditions in Brassicas.

A study was conducted under irrigated conditions to test the performance of improved cultivars of Indian mustard (B. juncea), Gobhi sarson (B. napus) and African sarson (B. carinata) under changing climatic conditions. The effect of cultivar, environment and their interactions were significant in mustard and canola gobhi sarson. Environment had significant impact on all the studied traits except for leaf area index (LAI). Cultivar x Year (G x Y) interaction was significant for flowering behavior, days to maturity, SPAD, photosynthetic active radiations (PAR), growth parameters, yield components and yield except photosynthesis photochemical efficiency, relative water content (RWC) and LAI. Cultivar RLC1 surpassed other B. juncea cultivars for yield and had low erucic acid ('0') while GSL1 (non canola), Hyola PAC401 (hybrid canola) and GSC6 (canola) of B. napus were superior in performance for seed yield and possessed low erucic and glucosinolate content ('00'). Higher seed yield was associated with more number of total siliquae/plant, seed weight, biomass, seeds/siliqua, SPAD and RWC. Correlation coefficient revealed high positive association for seed yield with days to maturity (0.639**), plant height (0.982**), secondary branches (0.826**), total siliquae/plant (0.913**), seed weight (0.761**) andbiomass (0.891**).