Bamboo stumps as mosquito larval habitats in Darjeeling Himalayas, India: A spatial scale analysis

Bamboo stumps can be a congenial breeding habitat of the mosquitoes. In view of this, a preliminary assessment of the dipteran immatures inhabiting the stumps of bamboo groves in the Darjeeling Himalayas was carried out at a spatial scale. Of the 104 stumps of Dendrocalamus hamiltoni surveyed, 70 were found to host immatures of three dipteran species, the mosquitoes Aedes aegypti and Culex quinquefasciatus and the midges Chironomus sp. in varying densities. Though the stumps varied in diameter, in each stump on average 12. 1 immatures were found. The abundance of the immatures was positively correlated with the diameter of the stumps (r=+0.382; P < 0.001) but negatively with the pH of the water present in the stumps (r=–0.336; P < 0.01). The coefficient of association was found to be +8.4 for the Ae. aegypti and Chironomus immatures, while in the rest of the species pair the association seemed to be independent. Thus it can be concluded that the stumps in the bamboo groves of Darjeeling Himalayas provides a favourable habitat for the mosquito and chironomid immatures.     

Safe sites for tree regeneration in wooded pastures: A case of associational resistance?

Abstract. Question: Are tree saplings in wooded pastures spatially associated with specific nurse structures or plants that facilitate tree sapling survival? Location: Wooded pastures in the Jura Mountains, Switzerland. Methods: In two sites, 73 km apart, we sampled 294 plots of 4 m², systematically distributed on 1 ha. We recorded number and height of all established Picea abies saplings (> 1 a of age and up to 40 cm in height), and visually estimated cover of rocks, shrubs, tree stumps, overhanging tree branches and unpalatable plant species. Results: Despite differences in site characteristics, we found overall positive effects of cover of unpalatable plants, rocky outcrops and tree stumps on the density of Picea saplings. Plots with tree stumps and higher cover of rocky outcrops and unpalatable plants were more likely to contain Picea saplings. Conclusions: Unpalatable plants, rocky outcrops and tree stumps seem to form safe sites for Picea saplings in this grazed system, improving their establishment and survival. Our findings support the idea that associational resistance drives the dynamics of wooded pastures, but experimental evidence for this hypothesis is still required.     

Sprout initiation and growth for three years after cutting in an abandoned secondary forest in Kyoto,Japan

Secondary forests in Japan have been abandoned and the ecosystem has degraded since the high economic growth period. We carried out cutting in January in three small areas of a long-abandoned secondary forest and investigated the sprout initiation and growth of woody plants for three years in order to reveal the early stage of sprout regeneration and to understand the sprouting ability and characteristics of each species for effective management. The percentage of sprouted stumps and the number of sprouting shoots was substantially maximized in autumn in the first year. These results suggest that autumn monitoring in the first year after cutting shows the maximum percentage of sprouted stumps and the maximum sprout number when cutting was conducted in the dormant season. With regards to species characteristics, Eurya japonica showed a low percentage of sprouted stumps in the lower plot, where the mean diameter at breast height for this species was smaller than in the other plots. The sprouting ability of E. japonica was deemed to be influenced by parent tree size. Ilex pedunculosa and Lyonia ovalifolia var. elliptica had high percentages of sprouted stumps and many sprouts. These species are useful for obtaining sprouting shoots (e.g., for firewood), but it is difficult to control their sprouting.     

Diversity of fungal endophytes in some medicinal plants of Himachal Pradesh,India

Fungal endophytes were isolated from surface sterilised leaf segments of five medicinal plants collected from Mandi district, Himachal Pradesh, India. A total of 373 fungal strains belonging to 15 fungal genera and 18 species, Aspergillus niger, A. flavus, A. clavatus, A. variecolor, Penicillium chrsogenum, Alternaria alternata, Curvularia lunata, Haplosporium sp., Phoma sp., Nigrospora sp., Colletotrichum sp., Cladosporium sp., Stemphylium sp., Fusarium sp., Geotrichum sp., Phomopsis sp., Trichoderma sp., Rhizopus sp. and some sterile mycelium were isolated from all the plants. The relative frequency, isolation rate and colonisation rates of endophytes were used to study the endophytic diversity. The results showed that the highest colonisation rate (93.05%) was observed in Adhathoda vasica, while it was 91.66% in Ocimum sanctum, 85% in Viola odorata, 82.81% Cannabis sativa and lowest (61.11%) in Withania somnifera. Moreover, reading the richness and diversity of the endophytic fungi, the highest was obtained for O. sanctum, W. somnifera and C. sativa having eight species each, while lowest (6 and 4) was obtained from A. vasica and V. odorata, respectively. As the role of endophytic organisms in defensive mechanisms of plants is now well established, the present study is an important step to find new and interesting endophytes among the medicinal plants.     

The Formation of Artificial Nitrogen-Fixing Symbioses with Rape (Brassica napusvar. napus) Plants in Nonsterile Soil

The treatment of rape plants grown in nonsterile soil with 2,4-dichlorophenoxyacetic acid (auxin-like growth-promoting substance) or their inoculation with the bacterial association Micrococcussp. + Rhodococcussp. and/or with the mixed nitrogen-fixing culture Azotobacter nigricans+ Bacillussp. led to the formation of paranodules on the rape roots. The introduced bacteria were detected both in the intercellular space and inside the cells of the paranodules and the rape roots. The nitrogen-fixing activity of the paranodulated plants was two times higher than that of the inoculated plants lacking paranodules and five times higher than that of the control (i.e., not inoculated) plants. The paranodulation led to a 40% increase in the crop yield of rape plants and provided for a statistically significant increase in the total nitrogen as well as protein nitrogen contents of the plants.     

Variability in Chemical Composition and Antimicrobial Activity of Mentha pulegium L. Essential Oil,Cultivated under Different Plant Growth Promoting Rhizobacteria

The aim of present work was to study the essential oil chemical composition and antimicrobial activity of cultivated Mentha pulegium L. under different plant growth promoting rhizobacteria (Pseudomonas fluorescens, Bradyrhizobium sp. and Sinorhizobium meliloti) individually and in consortium. Yield, in plants inoculated with Bradyrhizobium sp. and S. meliloti in consortium, increase significantly relative to control plants. GC and GC/MS analyses pointed to a qualitative and quantitative variability of components. The investigated essential oils were clustered into three chemotypes: piperitenone/1,8-cineol (40.9/29.4 %) chemotype in plants inoculated with Bradyrhizobium sp. individually, S. meliloti individually, and Bradyrhizobium sp. and S. meliloti in consortium, piperitone/menthone (41.8/33.8 %) chemotype in plants inoculated with P. fluorescens individually, P. fluorescens and Bradyrhizobium sp. in consortium, and P. fluorescens and S. meliloti in consortium and pulegone/menthol (47.9/31.5 %) chemotype in control plants. The antimicrobial activity, carried out by the disc diffusion method and the determination of the Minimum Inhibitory Concentration (MIC) against ten microorganisms, varied significantly according to the tested microorganism and the rhizobacterial species used individually or in consortium (inhibition zone: 8.5–33.5 mm; MIC: 0.25–2.5 μL/mL). Our findings provided useful indications to select interesting chemotype within M. pulegium, especially in perspective of its cultivation.     

Effect of Rhizobium sp. BARIRGm901 inoculation on nodulation,nitrogen fixation and yield of soybean (Glycine max) genotypes in gray terrace soil

Soybean plants require high amounts of nitrogen, which are mainly obtained from biological nitrogen fixation. A field experiment was conducted by soybean (Glycine max) genotypes, growing two varieties (Shohag and BARI Soybean6) and two advanced lines (MTD10 and BGM02026) of soybean with or without Rhizobium sp. BARIRGm901 inoculation. Soybean plants of all genotypes inoculated with Rhizobium sp. BARIRGm901 produced greater nodule numbers, nodule weight, shoot and root biomass, and plant height than non-inoculated plants. Similarly, inoculated plants showed enhanced activity of nitrogenase (NA) enzyme, contributing to higher nitrogen fixation and assimilation, compared to non-inoculated soybean plants in both years. Plants inoculated with Rhizobium sp. BARIRGm901 also showed higher pod, stover, and seed yield than non-inoculated plants. Therefore, Rhizobium sp. BARIRGm901 established an effective symbiotic relationship with a range of soybean genotypes and thus increased the nodulation, growth, and yield of soybean grown in gray terrace soils in Bangladesh.     

Biocontrol of tomato late blight with the combination of epiphytic antagonists and rhizobacteria

Control of tomato late blight (LB) in Brazil is heavily based on chemicals. However, reduction in fungicide usage is required in both conventional and organic production systems. Assuming that biological control is an alternative for LB management, 208 epiphytic microorganisms and 23 rhizobacteria (RB) were isolated from conventional and organically grown tomato plants and tested for antagonistic activity against Phytophthora infestans. Based on in vitro inhibition of sporangia germination and detached leaflet bioassays, four EP microorganisms (Aspergillus sp., Cellulomonas flavigena, Candida sp., and Cryptococcus sp.) were selected. These microorganisms were applied either singly or combined on tomato plants treated or not with the RB Bacillus cereus. On control plants, LB progress rate (r), area under disease progress curve, and final disease severity were high. Lowest values of final severity were recorded on plants colonized by B. cereus and treated with C. flavigena, Candida sp. and Cryptococcus sp. There was no reduction on disease severity in plants treated only with RB. Biological control of LB resulted in low values of r and final severity. Integration of biological control with fungicides, cultural practices, and other measures can contribute to manage LB on tomato production systems.     

Colonization of Fungi and Bacteria in Stumps and Roots of Scots Pine after Thinning and Treatment with Rotstop

The research areas were located in the Pisz Forest District, northeast Poland, in 10‐year‐old Scots pine (Pinus sylvestris L.) plantations, established in 2004 on a clear‐cut area. Reforestation was performed without a biological treatment against root pathogens, despite the presence of Heterobasidion annosum and Armillaria ostoyae in roots and stumps of trees growing previously. The aim of this research was to evaluate how thinning and treatment with the biological control agent Rotstop influences bacterial and fungal communities within roots and stumps. Twelve months after thinning, samples were collected from five stumps in each of two seasons, autumn and spring, from stands on two types of site, one previously forested and one agricultural (20 stumps in total). Wood samples were cultured on agar media, and (i) fungi in the upper part of the stump and (ii) in roots and (iii) bacteria in roots were genetically identified. Sequences were genetically identified by comparing sequences with records held in the GenBank database. We found great differences in the frequency of both fungi and bacteria in roots: they were more frequent (i) in healthy stumps compared to stumps infected with pathogens (H. annosum and A. ostoyae), (ii) in postagricultural soil than in forest soil and (iii) after spring rather than autumn biological treatment. The introduced species Phlebiopsis gigantea was only identified in the parts of the stumps which were above ground level. The bacterium Paenibacillus pini was associated with the presence of H. annosum infecting the stumps from the roots side. In areas seriously threatened by root pathogens, biological treatment can play only a limited role. It can spread to the upper part and impede the production of fruitbodies; however, it has no impact on the development of pathogens in deeper root areas.     

Efficacy and environmental fate of Chondrostereum purpureum used as a biological control for red alder (Alnus rubra)

A field trial to assess the ability of Chondrostereum purpureum to limit the resprouting of cut red alder (Alnus rubra) was established in British Columbia, Canada. Overall, 92% of stumps inoculated with C. purpureum died in the first year and 100% were dead by the second year. C. purpureum was thus as effective as the herbicide treatments Carbopaste and liquid glyphosate (12% Vision) and reduced resprouts to zero. Naturally occurring C. purpureum spores colonized about 40% of untreated cut stumps and about 20% of the stumps treated with chemical herbicides. The peak production of C. purpureum basidiocarps occurred about 22 months after the trial was established, with C. purpureum on 66% of treated stumps. The following year, the basidiocarps persisted on 23% of treated stumps. About 600 young red alder trees were cut to act as spore traps 2 years after trial establishment, when the most C. purpureum basidiocarps were present on treated stumps in the trial. These spore-trap trees were subsequently sampled, and PCR markers were used to verify and characterize 43 dikaryotic C. purpureum individuals, none of which were identified as the released isolate 2139. There was little difference in average band-sharing with the applied isolate among pre-trial (37% average) and spore-trap (38% average) populations. There was therefore no evidence that the C. purpureum strain applied inundatively to stumps in this trial was detectable on nontarget trees in the local area or had any measurable impact on the local C. purpureum population.     

Analysis of airborne pollen fall in Sakarya, Turkey

In this study, pollen grains were identified using Durham sampler in the atmosphere of Sakarya in 2000 and 2001. During these two years, a total of 10 805 pollen grains were recorded. A total of 5 386 pollen grains per cm² were recorded in 2000 and a total of 5 419 pollen grains per cm² in 2001. Pollen fall in the years 2000–2001 comprised grains belonging to 40 taxa and some unidentified pollen grains. Of these taxa, 22 belonged to arboreal and 18 taxa to non arboreal plants. Total pollen grains consisted of 69.45% grains from arboreal plants, 28.11% grains from non-arboreal plants and 2.44% unidentified pollen grains. In the region investigated, Gramineae, Pinus sp., Quercus sp., Cupressaceae/Taxaceae, Salix sp., Platanus sp., Populus sp., Carpinus sp., Fagus sp., Chenopodiaceae/Amaranthaceae, Xanthium sp., Moraceae, Corylus sp., Fraxinus sp., and Urticaceae released the greatest amount of pollen. The season of maximum pollen fall was from March to May, with a prevalence of arboreal pollen in the first months, and of pollen from non-arboreal plants in the last months of the year.     

Synergistic effect of soil pathogenic fungi and nematodes reducing bioprotection of Arbuscular mycorrhizal fungi on the grass Leymus arenarius

We examined the role ofarbuscular mycorrhizal fungi (AMF) in thebioprotection of the sand dune grass Leymus arenarius against soil fungi andnematodes. Six soil fungi (Fusariumnivale, Fusarium sp., Cladosporiumherbarum, Cladosporium sp., Phomasp., Sporothrix sp.) and four species ofnematodes (Pratylenchoidesmagnicauda, Paratylenchusmicrodorus, Rotylenchus goodeyi, Merlinius joctus) were isolated from a coastalsand dune in Iceland where a population of L. arenarius was declining in vigour. Acommercial AMF inoculum (Microbio Ltd. England)containing Glomus caledonium, G.fasciculatum, and G. mossae was used.Seedlings of L. arenarius were grownunder controlled conditions in sterile sand andsubjected to the following treatments: (1)control, (2) + AMF, (3) + AMF + soil fungi, (4)+ AMF + nematodes, (5) + AMF + nematodes + soilfungi, (6) + soil fungi, (7) + soil fungi +nematodes, (8) + nematodes. Mycorrhizal plantshad significantly the highest root dry weightof all treatments. Mycorrhizal plants hadsignificantly higher leaf dry weight thanplants in other treatments, with the exceptionof AMF inoculated plants exposed to nematodes. Mycorrhizal plants exposed to soil fungi andnematodes had significantly higher growthparameters except total number of leaves thanAMF inoculated plants exposed to both soilfungi and nematodes. Mycorrhizal plantssubjected to a dual application of soil fungiand nematodes did not vary significantly in anygrowth parameters from plants without AMF thatwere exposed to a dual application of soilfungi and nematodes. This suggests asynergistic effect of soil fungi and nematodesthat break down the protection of AMF againstpathogens. The results are discussed inrelation to plant dynamics of sand duneecosystems.     

Impact of biological (Rotstop) and chemical (urea) treatments on fungal community structure in freshly cut Picea abies stumps

To control the infections by root rot fungi Heterobasidion spp., surfaces of freshly cut Norway spruce stumps are covered either by a biological (Rotstop; spore suspension of competitive saprotrophic fungus Phlebiopsis gigantea), or by a chemical (35% aqueous solution of urea) compound. In Fennoscandia, Rotstop and urea are applied, respectively, on 47,000 ha and on 2000 ha of forestland each year. The aim of this work was to assess the impact of biological and chemical control on biodiversity in communities of non-target fungi in freshly cut (7-week-old) stumps. Isolation of fungi to pure culture was accomplished from 402 wood samples taken from 63 stumps, 21 treated with each of the compounds and 21 untreated. The isolations yielded 368 distinct fungal strains representing 47 species. Stump treatment led to decrease of species richness both in Rotstop-treated (by 15%) and in urea-treated (by 19%) stumps. Nevertheless, the stumps subjected to the biological compound were colonized mainly by the same fungi that occurred naturally in untreated stumps (Sorensen similarity indices; S_S=0.69; S_N=0.68). By contrast, chemical treatment strongly promoted stump colonization by Ascomycetes and Deuteromycetes, led to significant decrease of Zygomycetes, and almost completely eliminated Basidiomycetes (including Heterobasidion spp.). Thus, resemblance to a natural community was low (S_S=0.45; S_N=0.34). Rotstop treatment decreased significantly the extent of stump colonization by Heterobasidion spp., and increased that of P. gigantea. All strains of the latter were genetically identical among themselves and to the Rotstop strain. The mechanisms of biological and chemical control, and biodiversity aspects are discussed.     

The presence of <Emphasis Type="Italic">Zygina</Emphasis> sp. and <Emphasis Type="Italic">Puccinia myrsiphylli</Emphasis> reduces survival and influences oviposition of <Emphasis Type="Italic">Crioceris</Emphasis> sp.

A leaf beetle, Crioceris sp. (Coleoptera: Chrysomelidae), was introduced into Australia as a biological control agent of bridal creeper (Asparagus asparagoides L. Druce) during October 2002. Rearing of Crioceris sp. is labour intensive therefore all releases of Crioceris sp. have been under 1000 individuals, which may be too low to ensure establishment if high mortality and high competition with other agents occurs. The aim of this study is to understand how the presence of two well-established biocontrol agents, a rust fungus (Puccinia myrsiphylli (Thuem) Wint [Basidiomycota: Uredinales]) and a leafhopper (Zygina sp. [Hemiptera: Cicadellidae]), might influence Crioceris sp. establishment. Crioceris sp. neonate larvae were placed on bridal creeper plants with or without the leafhopper and/or rust. The number of larvae that pupated was reduced by 38 and 65% in the presence of the rust fungus and leafhopper, respectively and by 45% in the presence of both agents. As the area infected by the rust increased the area damaged by the leafhopper decreased. The rust appeared to be negatively impacted by the presence of the leafhopper. In a second experiment, female Crioceris sp. adults were given a choice between uninfested bridal creeper plants and those infested with the rust or the leafhopper. The females preferred to lay their eggs on plants without leafhoppers but did not seem to be deterred by the presence of the rust. Consequently, the performance and impact of Crioceris sp. on bridal creeper may be reduced if populations overlap with the other biocontrol agents in the field.     

The possible role of pathogenic fungi in local degeneration of Salvinia auriculata Aublet on Lake Kariba

A patchy degeneration of weed mats of Salvinia auriculata in the sheltered mouths of rivers draining into Lake Kariba was reported in 1962 to be associated with a fungal attack. Laboratory isolations from degenerating plants yielded a saprophytic Alternaria sp. and a parasitic Spicariopsis sp. Degenerating plants failed to transmit the disease when placed among healthy plants, and the results of inoculation experiments with spores of Spicariopsis sp. were inconsistent with this fungus being a primary pathogen. The characteristic feature of degeneration in the field was a mosaic of alternating ‘islands’ of diseased and healthy plants. Although the diseased plants showed the symptoms associated with Alternaria sp. and Spicariopsis sp., their characteristic distribution provided circumstantial evidence that degeneration was physiological in origin. This view was strengthened by the fact that sudd plants growing on degenerating areas of the Salvinia‘carpet’ were usually chlorotic. The presence of symptoms caused by the parasitic Spicariopsis sp. on degenerating plants could be explained by postulating that, after the plants have begun to degenerate, they are predisposed to infection by this fungus. The association of degeneration with a particular type of riverine site suggests that a seasonal investigation of the hydrobiological conditions accompanying the development of weed mats at such sites would indicate the type of factor responsible for the disease. The original hope for a biological control of Salvinia auriculata by means of a parasitic fungus remains a theoretical possibility.     

Effect of fungi–termite interaction on the chlorophyll content of three rice varieties grown on ultisol soil of Ikenne,south-west Nigeria

The effect of fungi–termite interaction on three rice varieties was conducted in a screen house at the Africa Rice Center (AfricaRice) Ibadan, Nigeria. Of the 10 fungi species (Fusarium verticilloides, Trichoderma sp., Aspergillus niger, Aspergillus flavus, Macrophoma sp., Neurospora sp., Botryodiplodia theobromae, Penicillum sp., Rhizopus sp. and Sclerotium rolfsii) isolated from termites, soil and rice plants, F. verticilloides, Trichoderma sp. and B. theobromae were used for the interaction study. Each fungus was inoculated singly and in combinations with termite into the root of each rice variety in potted soil. Leaf samples were taken to measure the chlorophyll content which is a major parameter to estimate effect of termite–fungi interaction. The chlorophyll content of the inoculated rice plants was significantly reduced when compared with the control. Fungi interaction with termite had significant reduction on the chlorophyll content. The synergistic relationship between the fungi and the termite was discussed.     

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.     

Enhancement of the efficiency of Cd phytoextraction using bacterial endophytes isolated from Chromolaena odorata,a Cd hyperaccumulator

Phytoextraction is a technique using a hyperaccumulator to remove heavy metals from soil. The efficiency of heavy metal uptake can be enhanced by the inoculation of endophytes. In this study, we isolated and identified 23 endophytes from Chromolaena odorata, a cadmium (Cd) hyperaccumulator that consisted of 19 bacteria, 2 actinomycetes and 2 fungi. All bacteria and fungi could produce at least 1 plant growth promoting factors. However, only 4 bacterial isolates; Paenibacillus sp. SB12, Bacillus sp. SB31, Bacillus sp. LB51, and Alcaligenes sp. RB54 showed the highest minimum inhibitory concentration (MIC) value (2.9 mM), followed by Exiguobacterium sp.RB51 (1.7 mM). Then, these 5 high-MIC bacteria and 1 low-MIC bacterium, Bacillus sp. LB15 were inoculated onto sunflower grown in soil supplemented with 250 mg/kg of Cd. After 60 days, all inoculated plants accumulated significantly higher Cd concentration than the non-inoculated counterparts, and those inoculated with strain LB51 showed the highest Cd accumulation and growth. Interestingly, strain LB15 with low MIC also enhanced Cd accumulation in plants. The results suggest that these bacteria, particularly strain LB51, could be applied to improve Cd accumulation in plants, and that bacteria with low MIC also have the potential to enhance the efficiency of phytoextraction.     

Ultrastructural Study of Cytoplasmic Inclusions in Plants Infected with Potyviruses

The ultrastructure of cell inclusions of different ornamental plants infected with several filamentous viruses of the potyviruses was studied at the transmission electron microscope. The plants examined were: Crocus sativus, Hyacinthus sp., Gladiolus sp., rhizomatous Iris, Muscari sp., Nerine bowdenii and Sparaxis sp. Differences in morphology of cylindrical inclusions have been used to separte the potyviruses in several subdivisions.     

l-tryptophan-assisted PGPR-mediated induction of drought tolerance in maize (Zea mays L.)

Drought is an important abiotic stress that limits the plant growth and productivity. Present investigation was aimed that plant growth-promoting rhizobacteria (PGPR) isolated from moisture-stressed area impart drought tolerance in plants and tryptophan may improve their efficiency. Pseudomonas sp. (1), Bacillus cereus and Bacillus pumilus (B. pumilus) were isolated from maize rhizosphere grown in irrigated fields, semi-arid region and arid region, respectively. Proteus sp. and Pseudomonas sp. (2) were isolated from rice rhizosphere grown in irrigated fields and raised bed. B. pumilus produced 5× more abscisic acid (ABA) in culture media than Pseudomonas sp. (1) by the addition of l-tryptophan. These inoculants also modulated the phytohormone content of maize leaves in a pot experiment. Higher ABA was produced by the application of B. pumilus and Pseudomonas sp. (2), while indole 3-acetic acid and gibberellic acid were found higher in Pseudomonas sp. (1) and Proteus sp. treated plants. Addition of l-tryptophan increased the concentration of all phytohormones in soil and leaves of maize. Maximum increase in relative water content, osmotic potential, protein content and photosynthetic pigments was recorded in B. pumilus treated maize plants. Under irrigated condition, response of Pseudomonas sp. co-inoculated with B. pumilus from arid field superseded while under drought stress the effect of later predominated. Bacillus pumilus can be used in the formulation of biofertilizer to alleviate drought stress in arid and semi-arid regions.