Rashmi Srivastava

Application of inorganic carrier-based formulations of fluorescent pseudomonads and Piriformospora indica on tomato plants and evaluation of their efficacy

Aims:  Fluorescent pseudomonads are widely used as bioinoculants for improving plant growth and controlling phytopathogenic fungi. Piriformospora indica (Pi), a symbiotic root endophyte, also has beneficial effects on a number of plants. The present study focuses on the improvement of growth yields of tomato plants and control of Fusarium wilt using inorganic carrier‐based formulations of two fluorescent pseudomonad strains (R62 and R81) and Pi.

Effect of formulated root endophytic fungus Piriformospora indica and plant growth promoting rhizobacteria fluorescent pseudomonads R62 and R81 on Vigna mungo

In the present investigation, the effect of three beneficial organisms (root endophytic fungus Piriformospora indica (Pi) and pseudomonads strains R62 and R81) and their four different consortia (Pi+R62, Pi+R81, R62+R81, Pi+R62+R81) was investigated on the plant Vigna mungo through their inorganic carrier-based (talcum powder and vermiculite) formulations. All the treatments resulted in significant increase in growth parameters under glasshouse as well as field conditions and showed a consistency in their performance on moving from glasshouse to field conditions. In glasshouse conditions, a maximum increase of 4.5-fold in dry root weight and 3.9-fold in dry shoot weight compared to control was obtained with vermiculite-based consortium formulation of Pi+R81. In field studies using vermiculite as carrier, a maximum enhancement of 3.2-fold in dry root weight, 3.0-fold in dry shoot weight, 8.4-fold in number of nodules and 4.0-fold in number of pods in comparison to control was obtained with the bio-inoculant formulation containing consortium of Pi+R81. The same treatment also caused the highest improvement of 1.9-fold in nitrogen content and 1.7-fold in phosphorus content, while the highest increase of 1.4-fold in potassium content was obtained with Pi alone.

Genome Sequences of Two Plant Growth-Promoting Fluorescent Pseudomonas Strains, R62 and R81

Plant growth-promoting rhizobacterial (PGPR) strains R62 and R81 have previously been isolated and characterized as part of the Indo-Swiss Collaboration in Biotechnology. Here we present the draft genome sequences of these two PGPR strains, with the aim of unraveling the mechanisms behind their ability to promote wheat growth.

Cow dung extract: a medium for the growth of pseudomonads enhancing their efficiency as biofertilizer and biocontrol agent in rice.

Some pseudomands are being utilized as biofertilizers and biopesticides because of their role in plant growth promotion and plant protection against root parasites, respectively. Two strains of Pseudomonas, P. jessenii LHRE62 and P. synxantha HHRE81, recovered from wheat rhizosphere, have shown their potential in field bioinoculation tests under rice-wheat and pulse-wheat rotation systems. Normally, pseudomonads are cultivated on synthetic media-like King’s B and used for inoculation on seeds/soil drench with talcum or charcoal as carrier material. Cow dung is being used for different purposes from the ancient time and has a significant role in crop growth because of the content in humic compounds and fertilizing bioelements available in it. Here, cow dung extract was tested as a growth medium for strains LHRE62 and HHRE81, in comparison with growth in King’s B medium. The log phase was delayed by 2 h as compared to growth in King’s B medium. The bacterial growth yield, lower in plain cow dung extract as compared to King’s B medium, was improved upon addition of different carbon substrates. Growth of rice var. Pant Dhan 4 in pot cultures was increased using liquid formulation of cow dung extract and bacteria as foliar spray, compared to their respective controls. Biocontrol efficacy of the bioagents was assessed by challenging rice crop with Rhizoctonia solani, a sheath blight pathogen. The growth promotion and biocontrol efficiencies were more pronounced in the case of mixed inocula of strains LHRE62 and HHRE81.

Role of Microbiologically Rich Compost in Reducing Biotic and Abiotic Stresses

Plant abiotic and biotic stress is related to unfavorable and environmental constraints. These stresses represent the principal cause of crop failure, decreasing average yields of major crops by more than 50%. Compost can be considered as a soil conditioner that contributes to soil fertility, structure, porosity, organic matter, water holding capacity and disease suppression. Composts suppress soil borne diseases and this suppression has been widely reported for Pythium spp., Phytophthora spp., Rhizoctonia spp. and Fusarium spp. Compost amendments also contribute to controlling foliar diseases, such as Puccinia spp., Alternaria solani and Pseudomonas syringae pv. syringae. Disease suppression by composts has been explained mainly by biotic mechanisms. The severity of soil-borne plant diseases is often reduced when microbiologically improved compost used as growth media. Wide variety of rhizosphere micro-organisms have been isolated and used as microbiological inoculants for improving plant growth and health. These include, arbuscular mycorrhizal fungi (AMF), plant growth promoting rhizobacteria (PGPR), nitrogen fixers and phosphorus solubilizing microorganisms (PSM). Utilization of compost with disease suppressive properties is a relatively new biological method of decreasing biotic stress in plant production. The main advantage of exploring the role of microbiologically rich compost in reducing biotic and abiotic stresses is that, it is a novel way to imitate the natural system occurring in ecosystems. Under saline conditions, compost was not completely efficient in correcting the detrimental effects of salt, but was able to mitigate them. Such an amendment may be used to enhance crop yield irrigated with saline waters or grown on saline soils. Compost amendments in soil are also efficient in combating the pH stress. The amendment of alkaline soils with composts has a positive effect on plant vigour. Molecular studies also showed a different profile of microorganisms in disease suppressive composts. This study shows a good approach to add-up value to compost, and make it more efficient in reducing biotic and abiotic stresses.

Screening of Resistant Varieties and Antagonistic Fusarium oxysporum forBiocontrol of Fusarium Wilt of Chilli

Chilli is an important vegetable/spice, and its socio-cultural role is remarkable worldwide. The enormous popularity and demand for chilli is providing a boost to the chilli industry, but its production is increasingly constrained by diseases. Chilli producers have reported Fusarium wilt, as the frequently encountered disease. The present investigation focuses on biological control, which is found effective to manage this disease. A survey was conducted at Uttarakhand and Uttar Pradesh states in India, for collection of soil and plant samples. A total of eighty isolates of Fusarium were isolated from these samples. Among these, forty eight isolates of Fusarium oxysporum were identified on the basis of morphological and molecular characteristics, using speciesspecific primers. Pathogenicity test on chilli was conducted. One isolate of F. oxysporum was found most virulent pathogen, while eleven isolates were non- pathogenic isolates. Isolate no. 65 was found most antagonistic towards F. oxysporum, under in-vitro dual culture assay. Thirty chilli varieties were screened for evaluation of resistance. Among these, two varieties were found resistant against the Fusarium wilt. The present investigation focused on recovery of antagonistic Fusarium and resistant varieties of chilli, for controlling and resisting wilt and improving the soil health.

Influence of IAA and ACC Deaminase Producing Fluorescent Pseudomonads in Alleviating Drought Stress in Wheat (Triticum aestivum)

Drought is one of the major constraints limiting agricultural production worldwide. Soil bacteria containing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and indole acetic acid (IAA) producing traits with the potential for the alleviation of drought stress in combination with plant growth promotion would be extremely useful tools in sustainable farming. The present study was undertaken with two drought-tolerant bacteria Pseudomonas fluorescens strain DPB15 and P. palleroniana strain DPB16 containing ACC deaminase activity as isolated from rainfed agriculture areas of Kumaun regions of Uttarakhand, India. There were two sets of pot trails, i.e., non-stressed (watered) and drought stressed (non-watered). The growth parameters were recorded after fifty-four days of growth. Bacterial inoculation enhanced the growth of wheat in terms of root and shoot biomass, height and foliar nutrient content in treated as compared to untreated plants. In addition, a significant increase in antioxidant activity (SOD, CAT, GPX and APX) was also observed where bacterial treatment improves the plant fitness by protecting it from the oxidative damage created by drought. A correlation study between non-enzymatic and enzymatic antioxidants demonstrated that a perfect positive significant correlation between SOD and Chl, GPX and Pro, CAT and H2O2, and CAT and TPC; a perfect negative correlation between TPC and H2O2; and for others parameters nonsignificant correlation were observed under water-stressed conditions.