PGPR: the treasure of multifarious beneficial microorganisms for nutrient mobilization, pest biocontrol and plant growth promotion in field crops.

Plant growth-promoting rhizobacteria (PGPR) have multifarious beneficial activities for plant growth promotion; act as source of metabolites, enzymes, nutrient mobilization, biological control of pests, induction of disease resistance vis-a-vis bioremediation potentials by phytoextraction and detoxification of heavy metals, pollutants and pesticides. Agrochemicals and synthetic pesticides are currently being utilized widely in all major field crops, thereby adversely affecting human and animal health, and posing serious threats to the environments. Beneficial microorganisms like PGPR could potentially substitute and supplement the toxic chemicals and pesticides with promising application in organic farming leading to sustainable agriculture practices and bioremediation of heavy metal contaminated sites. Among field crops limited bio-formulations have been prepared till now by utilization of PGPR strains having plant growth promotion, metabolites, enzymes, nutrient mobilization and biocontrol activities. The present review contributes comprehensive description of PGPR applications in field crops including commercial, oilseeds, leguminous and cereal crops to further extend the utilization of these potent groups of beneficial microorganisms so that even higher level of crop productivity and quality produce of field crops could be achieved. PGPR and bacteria based commercialized bio-formulations available worldwide for its application in the field crops have been compiled in this review which can be a substitute for the harmful synthetic chemicals. The current knowledge gap and potential target areas for future research have also been projected.

Modulation of plant growth and antioxidative defense system through endophyte biopriming in cotton (Gossypium spp.) and non-host crops.

Seed biopriming is very promising in improving seed health by mitigating various biotic and abiotic stresses. In this study, the effect of biopriming with cotton endophytes on seed germination and other growth parameters in host and non-host crops like wheat, sorghum, cowpea and chick pea was examined. The endophytes were antagonistic to cotton pathogens Corynespora cassiicola and Fusarium solani under in vitro. Among the eight endophytes, CFR-1 and CEL-48 were highly efficient with inhibition rates of 66.16% and 64.24% respectively against C. cassiicola, whereas CFL-34 was efficient against F. solani with more than 50% inhibition. Seed biopriming enhanced seed germination in cotton and non-host crops whereas seed vigor index was highest in bio-primed cotton. Moreover, growth promotion parameters were also enhanced upon endophyte biopriming. Total sugar content ranged from 5.46 to 7.54 mg/g F.W in cotton and highest was found in CFL-34 treated wheat (8.64 mg/g FW). There was an increase of 10-30% soluble protein in bioprimed cotton over control. Interestingly, the antioxidant potential in all the bio-primed crops was improved with increased catalase and peroxidase activity. Specific activity of catalase ranged from 0.42 to 1.90 µmol/min/mg protein in cotton, while highest activity was reported in CEL-48 primed wheat. The findings of this investigation emphasizes seed biopriming with endophytes for sustainable plant health management.

Mustard aphid infestation in India: development of forewarning models.

Aphid Lipaphis erysimi (Kaltenbach) infestation on mustard (Brassica juncea L.) account for considerable yield losses in India. Experimental data from six north Indian locations were used to study the role of weather on the incidence and development of mustard aphid. Temperature was found to regulate the aphid appearance and population build-up. In warm humid climate, time to attain peak population was relatively shorter than in cool climates. Aphids appeared mostly when the accumulated thermal time ranged between 810-847 degrees cd. Functional relations proposed in the present investigation between aphid incidence and peak population, using previous weeks weather and pest data for majority of the locations, could be used for taking any prophylactic/control measures.

Temperature thresholds and thermal requirements for the development of the rice leaf folder, Cnaphalocrocis medinalis.

The rice leaf folder, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) is a predominant foliage feeder in all the rice ecosystems. The objective of this study was to examine the development of leaf folder at 7 constant temperatures (18, 20, 25, 30, 32, 34, 35° C) and to estimate temperature thresholds and thermal constants for the forecasting models based on heat accumulation units, which could be developed for use in forecasting. The developmental periods of different stages of rice leaf folder were reduced with increases in temperature from 18 to 34° C. The lower threshold temperatures of 11.0, 10.4, 12.8, and 11.1° C, and thermal constants of 69, 270, 106, and 455 degree days, were estimated by linear regression analysis for egg, larva, pupa, and total development, respectively. Based on the thermodynamic non-linear optimSSI model, intrinsic optimum temperatures for the development of egg, larva, and pupa were estimated at 28.9, 25.1 and 23.7° C, respectively. The upper and lower threshold temperatures were estimated as 36.4° C and 11.2° C for total development, indicating that the enzyme was half active and half inactive at these temperatures. These estimated thermal thresholds and degree days could be used to predict the leaf folder activity in the field for their effective management.

Weed hosts of cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae).

The exotic cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) invaded India during 2006, and caused widespread infestation across all nine cotton growing states. P. solenopsis also infested weeds that aided its faster spread and increased severity across cotton fields. Two year survey carried out to document host plants of P. solenopsis between 2008 and 2010 revealed 27, 83, 59 and 108 weeds belonging to 8, 18, 10 and 32 families serving as alternate hosts at North, Central, South and All India cotton growing zones, respectively. Plant species of four families viz., Asteraceae, Amaranthaceae, Malvaceae and Lamiaceae constituted almost 50% of the weed hosts. While 39 weed species supported P. solenopsis multiplication during the cotton season, 37 were hosts during off season. Higher number of weeds as off season hosts (17) outnumbering cotton season (13) at Central over other zones indicated the strong carryover of the pest aided by weeds between two cotton seasons. Six, two and seven weed hosts had the extreme severity of Grade 4 during cotton, off and cotton + off seasons, respectively. Higher number of weed hosts of P. solenopsis were located at roadside: South (12) > Central (8) > North (3) zones. Commonality of weed hosts was higher between C+S zones, while no weed host was common between N+S zones. Paper furnishes the wide range of weed hosts of P. solenopsis, discusses their significance, and formulated general and specific cultural management strategies for nationwide implementation to prevent its outbreaks.

A new record of longicorn beetle, Acanthophorus rugiceps, from India as a root borer on physic nut, Jatropha curcas, with a description of life stages, biology, and seasonal dynamics.

Longicorn beetle, Acanthophorus rugiceps Gahan (Coleoptera: Cerambycidae), is reported for the first time as a confirmed host on physic nut, Jatropha curcas L. (Malpighiales: Euphorbiaceae), from India, causing extensive damage to roots. Plants of three years age and above were prone to attack by this pest. In a six year study beginning in 2005, about 11.3 percent of plants in a 16.25 acre physic nut plantation were severely damaged by A. rugiceps. Life stages of A. rugiceps, including egg, larvae, pupae, and adult, are described with a note on their habitat, biology, and behavior. Strategies to manage this pest on physic nut are discussed.

Identification of virulent isolates of the entomopathogenic fungus Nomuraea rileyi (F) Samson for the management of Helicoverpa armigera and Spodoptera litura (identification of virulent isolates of N. rileyi).

Eleven geographical isolates of the entomopathogenic fungus Nomuraea rileyi (Farlow) Samson of Helicoverpa armigera (Hubner)/Spodoptera litura (Fabricius) origin were studied for efficacy against the two host insects. Laboratory bioassays at a concentration of 2 x 10(8) conidia ml(-1) indicated that N. rileyi isolates of S. litura origin were better in terms of time taken for mycosis and mortality in both the test larvae: S. litura (77-80% mortality in 7 days) and H. armigera (79-85% in 8 days). Among the isolates of S. litura origin, geographical isolates from Hyderabad and Karimnagar were superior in terms of high percent kill as well as 100% germination of conidia within 48 h. Fastest germination was observed with Karimnagar isolate followed by Hyderabad isolate. Conidial yield was highest on barley-carrot extract-yeast extract medium. However in terms of material cost, barley-yeast extract medium was the lowest. The Karimnagar isolate of S. litura origin gave the highest conidial yield on barley-yeast extract medium. Chitinolytic enzyme profiles of different isolates revealed polymorphism in all the isolates from S. litura origin. Overall among the parameters studied the best traits were found in the Karimnagar isolate of S. litura origin.

Cost-effective multiplication of the entomopathogenic fungus Nomuraea rileyi (F) Samson.

Cost-effective and rapid multiplication of Nomuraea rileyi is reported. The spore yields in semi-synthetic media were comparable or significantly higher to the standard medium. Maltose and peptone, carbon and nitrogen sources could be effectively replaced with 2% barley extract and 1% soybean extract respectively. However, replacement of yeast extract with dry yeast resulted in lower spore yields. Sporulation of the fungus multiplied on solid substrate was possible only when the bags used had a 0.2 microm filter to facilitate passive exchange of sterile air. A high spore yield of 2.8 x 10(9)/g of substrate was realized on crushed sorghum.