Diallel analysis in groundnut (Arachis hypogaea L.)

Summary An 8 × 8 full diallel experiment based on 4 bunch plus 4 spreading types of groundnut (Arachis hypogaea L.) was conducted over three environments. For both number of pods and pod yield, additive, nonadditive and reciprocal cross effects were detected and these were also influenced by changes in environments. For number of pods additive genetic variance was predominant whereas it was approximately equal to non-additive genetic variance for pod yield. Graphical analysis revealed the presence of strong non-allelic interaction for number of pods whereas for pod yield absence of dominance and/or presence of non-allelic interaction was evident.Part of Ph.D. Thesis of the first author     

Early generation intermating for yield improvement in groundnut (Arachis hypogaea L.)

Summary Seeds of 4 crosses of groundnut (Arachis hypogaea L.), Robut 33-1 x Chico, Robut 33-1 x NC Ac 17090, Robut 33-1 x PI 298115 and MK 374 x GAUG 1, were irradiated with 30 kR. In the F₁, some branches of each plant were intermated with other plants at random and others selfed in each cross to produce S₂ and F₂ seeds. They were evaluated for pod yield, shelling percentage and 100-kernel weight. The frequency of plants superior to F[in1] was much higher in S₂ than in F₂, which was, in general, true for the values of yield and its components. The S₂ and F₂ were advanced to third generation by selfing. The families descending from S₂ showed clear superiority over those from F₂. The reason for such superiority was suggested to be the recombination of genes from the upper and lower ends of the genotypic distribution under intermating.     

Nonparametric approach to multitrait selection for yield in groundnut (Arachis hypogaea L.)

Summary Eight characters related to nitrogen fixation and pod development measured 30 days after flowering were evaluated for their correct grading of the relative yield performance of 17 genetically diverse lines of groundnut (Arachis hypogaea L.). Each line was assigned a high or low yield status based on its pod yield, shelling percentage, and 100-kernel weight. Seventeen character combinations were examined for their relative merit in correct identification of the yield status of lines. The character sets, nitrogenase activity alone or in combination with nitrogen percent or shoot weight identified the status of 77% of lines correctly. The extent to which various characters accounted for the variation in pod yield was also checked by multiple regression analysis. While the character combination, nitrogen percent plus leaf area explained 75% of variation in pod yield, nodule mass, nitrogenase activity, and leaf area occurred in some other combinations that explained yield variation to a lesser extent. These analyses point to the profitability of involving crop physiological traits such as leaf area and nitrogen percent in selecting for relative yield performance in groundnut.IARI Regional Station, Tutikandi, Simla 171004, IndiaNational Research Center for Groundnut, Timbawadi, Junagadh 362015, India     

Phenolic acid metabolism of groundnut (Arachis hypogaea L.) plants inoculated with VAM fungus and Rhizobium

Mycorrhizal and Rhizobiuminoculation resulted in a significant increase in the quantities of phenoliccompounds in roots and shoots of groundnut plants, as compared to uninoculatedplants. Production of some new compounds, and increase in the activity of theenzymes peroxidase and polyphenol oxidase, following inoculation was observed.Accumulation of phenolics and the activation of oxidative enzymes were morepronounced in the dual inoculated plants.     

Growth and yield of groundnut (Arachis hypogaea L.) plants in soil inoculated with Aspergillus niger Van Tieghem

Aspergillus niger, a soil-borne fungus is a causative agent of hypocotyl malformations in infected groundnut (Arachis hypogaea L.) plants, but its effect on yield is unknown. This study sought to determine its effect on growth and yield. Seeds of Chinese and JL45 varieties were sown in soil inoculated with A. niger. Fresh and dry weights of the shoots and roots were taken at 10-day intervals. Nodule count was done at 30 days after emergence and subsequently at 10-day intervals. Pods of 20 plants each from inoculated and uninoculated soils were harvested. Growth was suppressed in plants grown on A. niger inoculated soil. Eight-day old plants grown in inoculated soil developed curvatures on their hypocotyls. Nodulation was suppressed (p < 0.05) in plants grown in inoculated soil. Although growth was suppressed in plants grown on inoculated soil, yield of both varieties of groundnut was not affected.     

Inheritance of resistance to groundnut rosette virus in groundnut (Arachis hypogaea L.)

A method of field screening groundnut seedlings for resistance to groundnut rosette virus (GRV), by means of which over 97% incidence was induced in rows of susceptible test plants, was developed at Chitedze Research Station in Malawi. Two GRV-resistant Virginia cultivars (RG 1 and RMP 40) were crossed with three susceptible cultivars, one from each of the Spanish (JL 24), Valencia (ICGM 48) and Virginia (Mani Pintar) botanical groups. Twelve F₁ reciprocal crosses and their F₂ and backcross generations were produced and the material screened in nurseries in 1985/86 and 1986/87. Seedlings raised from plants which did not become infected in the field were inoculated in the glasshouse in order to eliminate susceptible escapees. The numbers of diseased and healthy individuals in each population were subjected to χ² tests. In the majority of the F₂ populations a good fit was obtained for a ratio of one resistant to 15 susceptible plants, a ratio to be expected if resistance to GRV were determined by a pair of independent complementary recessive genes. This was further supported by data from backcross generations.     

Root turnover of groundnut (Arachis hypogaea L.) in soil tubes

Five groundnut cultivars were grown in transparent tubes of pasteurized loam compost in growth-chamber conditions. Weekly tracings were made of all the roots visible through the walls of the tubes. White roots were assessed as living, and brown or decayed roots as dead; this correlated with microscopical assessments of root viability based on cytoplasmic staining with neutral red followed by plasmolysis.For all five cultivars, root laterals began to die 3–4 weeks after plants were sown. Death of root laterals progressed down the soil profile with time, while new roots were produced successively deeper from the extending taproot. The half-life of individual roots was calculated as 3.7–4.4 weeks for all cultivars, based on assessments of the roots that died up to plant maturity (14–20 weeks, depending on cultivar). At maturity, 73–83% of the cumulative length of root systems had died. The onset and rate of root death were not related to onset of flowering or pod-filling; instead, the peak times of root death at different distances down the root system were related to earlier (3–5 week) peak times of root production in those regions. The net result of root turnover was that, despite continued new root production, the maximum length of living (white) roots of each cultivar was recorded at 2–4 weeks after sowing. Death of the earliest formed root laterals was also observed in the first five weeks after sowing of groundnut in an experimental field plot in Malawi. Progressive root turnover is considered to be a normal feature of groundnut, perhaps representing an energy-economy strategy.     

RAPD analysis of induced mutants of groundnut (Arachis hypogaea L.)

Radiation-induced mutants of groundnut cv. Spanish Improved showing distinct morphological differences and the parent were screened for RAPD variability. The analysis revealed characteristic band differences among the 12 mutants and the parent. The polymorphic RAPD bands were dominant in the F₁ and segregated in a Mendelian fashion in the F₂. The RAPD technique brought out greater genome variability than RFLP.     

Phylloplane bacteria increase seedling emergence, growth and yield of field-grown groundnut (Arachis hypogaea L.)

AIM: To isolate and characterize groundnut-associated bacterial isolates for growth promotion of groundnut in field. METHODS AND RESULTS: Three hundred and ninety-three groundnut-associated bacteria, representing the geocarposphere, phylloplane and rhizosphere, and endophytes were applied as seed treatment in greenhouse. Maximum increase in plant biomass (up to 26%) was observed following treatment with a rhizosphere isolate identified as Bacillus firmis GRS 123, and two phylloplane isolates Bacillus megaterium GPS 55 and Pseudomonas aeruginosa GPS 21. There was no correlation between the production of L-tryptophan-derived auxins and growth promotion by the test isolates. Actively growing cells and peat formulations of GRS 123 and GPS 55, and actively growing cells of GPS 21, significantly increased the plant growth and pod yield (up to 19%) in field. Rifampicin-resistant mutants of GRS 123 and GPS 21 colonized the ecto- and endorhizospheres of groundnut, respectively, up to 100 days after sowing (DAS), whereas GPS 55 was recovered from both the habitats at 100 DAS. CONCLUSION: Seed bacterization with phylloplane isolates promoted groundnut growth indicating the possibility of isolating rhizosphere beneficial bacteria from different habitats. SIGNIFICANCE AND IMPACT OF THE STUDY: Identification of phylloplane bacteria as effective plant growth-promoting rhizobacteria (PGPR) broadens the spectrum of PGPR available for field application.     

Pod development of groundnut (Arachis hypogaea L.) in solution culture

Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight.     

Variation and inheritance of the arachin polypeptides of groundnut (Arachis hypogaea L.)

Summary Variation in the arachin polypeptides of groundnut genotypes was observed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Three regions could be observed on the electropherogram. Region 1, corresponding to conarachin, did not show any variation; region 2, consisting of arachin acidic subunits, showed variation; region 3, containing the arachin basic subunits, did not show any variation. There are four varietal classes of arachin polypeptide patterns: class A comprised three acidic subunits of arachin of molecular weights 47.5, 45.1 and 42.6 kd and a basic subunit of 21.4 kd; class B, with three acidic subunits of molecular weights 47.5, 45.1 and 41.2 kd and a basic subunit of 21.4 kd; class C of an additive pattern of class A and class B; class D, of two acidic polypeptides of 47.5, 45.1 kd and the basic 21.4 kd subunit. Of the 90 genotypes studied, 73% belong to class A, 15% to class B and 6% each to class C and D. Analysis of F₂ seeds from a cross between class A and class B genotypes showed that the two polypeptides (42.6 kd and 41.2 kd) are coded by nonallelic genes and also revealed that class C and class D patterns arose as a result of hybridisation between class A and class B. A. monticola, the progenitor of A. hypogaea, showed a pattern similar to the additive pattern of class A and class B while some diploid Arachis species had the 41.2 kd polypeptide. Based on arachin polypeptide patterns the probable origin of A. hypogaea has been suggested.     

Resistance in groundnut (Arachis hypogaea L.) to Aphis craccivora (Koch).

The behaviour, development and reproductive capacity of Aphis craccivora, vector of a number of groundnut viruses, are compared on a range of susceptible and resistant genotypes. Field trials demonstrated no significant difference between genotypes in the rate of arrival of alates, but population development was slower, and subsequent population decline faster, on the genotype EC 36892 (ICG 5240). Behavioural studies in the screenhouse, likewise showed no inhibition to alighting onto EC 36892 though choice tests demonstrated a significant redistribution of the population in favour of the susceptible genotype TMV 2 (ICG 221) over the following 10 h. In clip cage experiments, development was faster and nymphal numbers were higher on the genotype TMV 2 compared to EC 36892.     

Differences in yield determining processes of groundnut (Arachis hypogaea L.) genotypes in varied drought environments1

Thirty-six groundnut gentoypes of varied origin were evaluated for their yield, crop growth rates (C), and partitioning to reproductive sinks (p) in three trials. In the trials irrigation and sowing date were used to vary the amount of water available either throughout the crops' life, or through the grain filling phase. Genotype performance across the five environments for these attributes showed that although differences in C existed, differences in the stability of the partitioning were the dominant attribute of genotypes adapted to the drought prone Sahelian region. Data suggested that these differences were more attributable to tolerance to temperature and/or humidity than water stress. Over all treatments canopy temperatures relative to air (CATD) were strongly correlated with the C observed, but not so with yield; and differences between genotypes in the relationship between C and CATD were not statistically significant.     

Response of groundnut (Arachis hypogaea L) toRhizobium inoculation in the field: Problems and prospects

Summary A successfulRhizobium inoculant strain needs to be more competitive than native soil rhizobia in forming nodules and to be effective in fixing nitrogen. Persistence of the strain from one season to the next will be an added advantage, since it eliminates the need to inoculate every season. Earlier studies indicated that groundnut,Arachis hypogaea, seldom responds toRhizobium inoculation in soils already containing rhizobia which nodulate groundnut. However, the results of seven years of research at ICRISAT have opened up the prospect of inoculating groundnut in such soils. These experiments indicate that inoculating with sufficient numbers of an effectiveRhizobium strain, NC 92, applied as a liquid slurry below the seed, increased yields of certain groundnut cultivars. Similar results were reported from other research centres in India. Inoculation with NC 92 for two consecutive seasons increased the proportion of nodules formed by this strain, from 25–32% in the first season to 41–54% in the second season, indicating that this strain can persist in the field for the following season. This paper also discusses results of experiments relating to host cultivar specificity and some possible problems in applying this information to farmers' fields. Strain NC 92 also produces a siderophore, an iron chelating compound, which may help in the iron nutrition of the plant.

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Resumen Respuesta del maní (Arachis hypogaeaL.)a la inoculación con Rhizobiumen el campo. Problemas y perspectivas.La inoculación conRhizobium para tener exito debe de realizarse con una cepa que sea competitivamente mejor que las cepas nativas del suelo en cuestión, en relación a la habilidad para formar nódulos y a la eficacia en la fijación de nitrógeno. La persistencia de la cepa de una temporada para otra es una caracteristica deseable ya que elimina la necesidad de reinocular cada temporada. Estudios previos indicaban que el maní (Arachis hypogaeae) raras veces responde a la inoculación conRhizobium en suelos que ya contienenRhizobium especificos. Sin embargo los resultados de siete años de investigaciones en ICRISAT han abierto nuevas perspectivas para la inoculación del maní en dichos suelos. Esta experiencias indican que la inoculación, en cantidades suficientes de una cepa deRhizobium eficaz (NC 92) aplicada en forma de liquido viscoso bajo la semilla incrementa el rendimiento de ciertos cultivars de mani. Resultados semejantes se han observado en otros centros de investigación en India.La inoculación de la cepa NC 92 durante dos años consecutivos incrementó la proporción de nódulos formados desde 25–32% en la primera temporada hasta 41–54% en la segunda indicando pues la persistencia de dicha cepa en el suelo de una a otra temporada. Este trabajo también evalua los resultados de investigaciones relacionando la especificidad del inóculo con la posible problemática que conlleva la aplicación de esta informacion por el agricultor.

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Résumé Réponse de l'arachide (Arachis hypogeaL.)à l'inculation de Rhizobiumdans les champs. Problèmes et perspectives.Pour être couronnée de succès, une souche deRhizobium inoculée doit supplanter les rhizobiums natifs du sol en ce qui concerne la formation de nodules et doit fixer l'azote efficacement. La persistance de la souche d'une saison à l'autre, rendant inutile la répétition saisonnière de l'inoculation, est un avantage supplémentaire. Des études antérieures ont montré que l'arachide (Arachis hypogea) ne répond que rarement à l'inoculation dans des sols contenant déjà des rhizobiums capables de noduler cette plante. Cependant, les résultats de sept années de recherches éffectuées à l'ICRISAT ont ouvert des possibilités quant à l'inoculation dans ce type de sols. Ces expériences montrent qu'une bouillie liquide d'une souche efficace deRhizobium (NC 92), répandue en quantité suffisante sous les graines, augmente le rendement de certains cultivars d'arachide. Des résultats similaires ont été rapportés par d'autres centres de recherches en Inde. L'inoculation de NC 92 pendant deux saisons consécutives a augmenté la proportion des nodules formés par cette souche de 25 à 32% pour la première saison, et de 41 à 54% pour la seconde, ce qui indique que cette souche peut persister dans le sol d'une saison à l'autre. Dans cet article sont également discutés les résultats d'expériences concernant la spécificité de l'hôte et quelques problèmes concernant l'utilisation de ces informations par les agriculteurs. La souche NC 92 produit aussi un sidérophore, agent complexant du fer pouvant jouer un rôle dans le métabolisme de ce métal chez la plante.

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Submitted as ICRISAT J. A. No. 475.     

Potential for plant growth promotion in groundnut (Arachis hypogaea L.) cv. ALR-2 by co-inoculation of sulfur-oxidizing bacteria and Rhizobium

The use of Rhizobium inoculant for groundnut is a common practice in India. Also, co-inoculation of Rhizobium with other plant growth-promoting bacteria received considerable attention in legume growth promotion. Hence, in the present study we investigated effects of co-inoculating the sulfur (S)-oxidizing bacterial strains with Rhizobium, a strain that had no S-oxidizing potential in groundnut. Chemolithotrophic S-oxidizing bacterial isolates from different sources by enrichment isolation technique included three autotrophic (LCH, SWA5 and SWA4) and one heterotrophic (SGA6) strains. All the four isolates decreased the pH of the growth medium through oxidation of elemental S to sulfuric acid. Characterization revealed that these isolates tentatively placed into the genus Thiobacillus. Clay-based pellet formulation (2.5 x 10(7) cf ug(-1) pellet) of the Thiobacillus strains were developed and their efficiency to promote plant growth was tested in groundnut under pot culture and field conditions with S-deficit soil. Experiments in pot culture yielded promising results on groundnut increasing the plant biomass, nodule number and dry weight, and pod yield. Co-inoculation of Thiobacillus sp. strain LCH (applied at 60 kg ha(-1)) with Rhizobium under field condition recorded significantly higher nodule number, nodule dry weight and plant biomass 136.9 plant(-1), 740.0mg plant(-1) and 15.0 g plant(-1), respectively, on 80 days after sowing and enhanced the pod yield by 18%. Also inoculation of S-oxidizing bacteria increased the soil available S from 7.4 to 8.43 kg ha(-1). These results suggest that inoculation of S-oxidizing bacteria along with rhizobia results in synergistic interactions promoting the yield and oil content of groundnut, in S-deficit soils.     

The first SSR-based genetic linkage map for cultivated groundnut (Arachis hypogaea L.)

Molecular markers and genetic linkage maps are pre-requisites for molecular breeding in any crop species. In case of peanut or groundnut (Arachis hypogaea L.), an amphidiploid (4X) species, not a single genetic map is, however, available based on a mapping population derived from cultivated genotypes. In order to develop a genetic linkage map for tetraploid cultivated groundnut, a total of 1,145 microsatellite or simple sequence repeat (SSR) markers available in public domain as well as unpublished markers from several sources were screened on two genotypes, TAG 24 and ICGV 86031 that are parents of a recombinant inbred line mapping population. As a result, 144 (12.6%) polymorphic markers were identified and these amplified a total of 150 loci. A total of 135 SSR loci could be mapped into 22 linkage groups (LGs). While six LGs had only two SSR loci, the other LGs contained 3 (LG_AhXV) to 15 (LG_AhVIII) loci. As the mapping population used for developing the genetic map segregates for drought tolerance traits, phenotyping data obtained for transpiration, transpiration efficiency, specific leaf area and SPAD chlorophyll meter reading (SCMR) for 2 years were analyzed together with genotyping data. Although, 2–5 QTLs for each trait mentioned above were identified, the phenotypic variation explained by these QTLs was in the range of 3.5–14.1%. In addition, alignment of two linkage groups (LGs) (LG_AhIII and LG_AhVI) of the developed genetic map was shown with available genetic maps of AA diploid genome of groundnut and Lotus and Medicago. The present study reports the construction of the first genetic map for cultivated groundnut and demonstrates its utility for molecular mapping of QTLs controlling drought tolerance related traits as well as establishing relationships with diploid AA genome of groundnut and model legume genome species. Therefore, the map should be useful for the community for a variety of applications. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mobilization and exudation of photo-assimilated14C by developing pods of groundnut (Arachis hypogaea L.)

Summary ‘Pod washings’ were collected from groundnut at three hour intervals for 24 hours after feeding the plants with¹⁴CO₂. Low radioactivity was found in the first four ‘Pod washings’ of 10 day old pods and the radioactivity increased with time. Highest radioactivity was found in washings of 20 and 30 day old pods and was twice the activity found in the washings of 50 day old pods. The radioactivity of both ethanol-soluble and insoluble fractions in pods was determined. The radioactivity mobilized into the pods increased with age and it was highest in 50 day old pods. The influence of the pod exudates on geocarposphere microflora during pod development is discussed.     

In vitro flowering and pod formation from cotyledons of groundnut (Arachis hypogaea L.)

Summary The response of groundnut cotyledons to the presence of various growth regulators in concentrations from 0.1 to 5 mg/l has been studied in detail using several genotypes of groundnut on two different media. Cotyledons with embryo axis, cultured on Blaydes' medium with cytokinins, produced shoots, in the axils of which 2–7 flower buds could be seen. The frequency of flower bud induction in general increased with increasing concentrations of cytokinins, the optimal levels being 3 mg/l of KN or 4 mg/l of BAP. Cotyledons without embryo axis, cultured on Blaydes' medium with BAP (0.5 mg/l), produced a cluster of flower buds directly, ranging in number from 8–28, without any vegetative growth. Excised embryo axes cultured on the same medium gave plantlets without flower buds. The growth regulators IAA, NAA, GA₃ and ABA failed to induce flower buds in independent treatments. However, lower concentrations of IAA and NAA in combination with cytokinins exerted a positive influence on flowering. The blooming of the flower buds was facilitated on media supplemented with low concentrations of cytokinins. Six percent of the induced flowers resulted in gynophore development and ultimately formed pods when cultured under complete dark conditions in modified MS medium supplemented with kinetin.     

Genetic variation for VA mycorrhiza-dependent phosphate mobilisation in groundnut (Arachis hypogaea L.)

Nine cultivars of groundnut (Arachis hypogaea L.) were grown in a soil poor in available N or P. There was clearly genetic variation of characteristics indicative of VA mycorrhiza-dependent phosphate mobilisation, namely, VA mycorrhiza fungal spore count (SC), percentage of infection (IF) by VA mycorrhizal fungi (VAMF) and acid and alkaline phosphatase activities. Among the cultivars, one was non-nodulating with low values for all characteristics and in another experiment, this non-nodulating cultivar, one of its parents (PI 259747), a national check (Robut 33-1) and the highest yielding cultivar among the original nine (NFG 7), were grown and investigated for various P-mobilising properties and yield. The linear regression coefficient of pod yield on % VAMF infection was significant in both the experiments. Additionally, many of the correlation coefficients of pod yield and VAM dependent characteristics were positive and significant. From consideration of published evidence, it seems possible to breed for the desirable reinforcing effects of infestation, by VAMF and Rhizobium that can ultimately improve the productivity of groundnuts.     

Growth promotion and yield enhancement of peanut (Arachis hypogaea L.) by application of plant growth-promoting rhizobacteria

Although plant growth-promoting rhizobacteria (PGPR) have been reported to influence plant growth, yield and nutrient uptake by an array of mechanisms, the specific traits by which PGPR promote plant growth, yield and nutrient uptake were limited to the expression of one or more of the traits expressed at a given environment of plant–microbe interaction. We selected nine different isolates of PGPR from a pool of 233 rhizobacterial isolates obtained from the peanut rhizosphere on the basis of ACC-deaminase activity. The nine isolates were selected, initially, on the basis of germinating seed bioassay in which the root length of the seedling was enhanced significantly over the untreated control. All the nine isolates were identified as Pseudomonas spp. Four of these isolates, viz. PGPR1, PGPR2, PGPR4 and PGPR7 (all fluorescent pseudomonads), were the best in producing siderophore and indole acetic acid (IAA). In addition to IAA and siderophore-producing attributes, Pseudomonas fluorescens PGPR1 also possessed the characters like tri-calcium phosphate solubilization, ammonification and inhibited Aspergillus niger and A. flavus in vitro. P. fluorescens PGPR2 differed from PGPR1 in the sense that it did not show ammonification. In addition to the traits exhibited by PGPR1, PGPR4 showed strong in vitro inhibition to Sclerotium rolfsii. The performances of these selected plant growth-promoting rhizobacterial isolates were repeatedly evaluated for 3 years in pot and field trials. Seed inoculation of these three isolates, viz. PGPR1, PGPR2 and PGPR4, resulted in a significantly higher pod yield than the control, in pots, during rainy and post-rainy seasons. The contents of nitrogen and phosphorus in soil, shoot and kernel were also enhanced significantly in treatments inoculated with these rhizobacterial isolates in pots during both the seasons. In the field trials, however, there was wide variation in the performance of the PGPR isolates in enhancing the growth and yield of peanut in different years. Plant growth-promoting fluorescent pseudomonad isolates, viz. PGPR1, PGPR2 and PGPR4, significantly enhanced pod yield (23–26%, 24–28% and 18–24%, respectively), haulm yield and nodule dry weight over the control in 3 years. Other attributes like root length, pod number, 100-kernel mass, shelling out-turn and nodule number were also enhanced. Seed bacterization with plant growth-promoting P. fluorescens isolates, viz. PGPR1, PGPR2 and PGPR4, suppressed the soil-borne fungal diseases like collar rot of peanut caused by A. niger and PGPR4 also suppressed stem rot caused by S. rolfsii. Studies on the growth patterns of PGPR isolates utilizing the seed leachate as the sole source of C and N indicated that PGPR4 isolate was the best in utilizing the seed leachate of peanut, cultivar JL24. Studies on the rhizosphere competence of the PGPR isolates, evaluated on the basis of spontaneous rifampicin resistance, indicated that PGPR7 was the best rhizoplane colonizer and PGPR1 was the best rhizosphere colonizer. Although the presence of growth-promoting traits in vitro does not guarantee that an isolate will be plant growth promoting in nature, results suggested that besides ACC-deaminase activity of the PGPR isolates, expression of one or more of the traits like suppression of phytopathogens, solubilization of tri-calcium phosphate, production of siderophore and/or nodulation promotion might have contributed to the enhancement of growth, yield and nutrient uptake of peanut.