Peanut Rhizosphere Research Articles

Study of Microbial Population and Enzyme Activities in Intercropped Peanut Rhizosphere with Different Nutrient Application

The aim of this study was to investigate the effect of different levels of chemical fertilizers (CF) alone or in combination with farmyard manure (FYM) under lime or no lime amelioration on biological properties of the rhizosphere soil of peanut, grown as intercrop with sabai grass (Eulaliopsis binata (Retz.) C.E. Hubb) in an acid lateritic soil. The effect of five fertilization levels viz., no CF (F0), CF @ 20:40:30 (F1), CF @ 40:80:60 (F2) kg ha -1

RHIZOBAKTERIA PENGHASIL FITOHORMON IAA PADA RHIZOSFIR TUMBUHAN SEMAK KARAMUNTING, TITONIA, DAN TANAMAN PANGAN

Rhizobacteria from various research results have shown an important role in producing organic compounds (phytohormone) which can affect plant physiological processes even in low concentrations. This research aimed to study the production of Indole Acetic Acid (IAA) in several plants rhizosphere, to calculate the rhizobacteria population that able to produce and synthesize IAA and to isolate these rhizobacteria from several rhizospheres of cultivated plants (maize and peanut) and bush plant i.e. karamunting (Rhodomyrtus tomentosa) and titonia (Tithonia diversifolia). All plants and crops were obtained from experimental station Faculty of Agriculture Andalas University. Further research is conducted in Soil Biology Laboratory Faculty of Agriculture. Experimental design in this study was not used but the data obtained from 3 replications tested by T test at 5% level and if it was significantly different it would be followed by further HSD tests at 5% level. Highest content of IAA was found in the peanut crop (67.30 ppm), followed by maize (53.61 ppm) and 28.53 ppm for titonia. Whereas the lowest content of IAA was found in karamunting rhizosphere, it was 22.29 ppm. The highest amount of rhizobacteria was obtained from peanut rhizosphere followed by maize and titonia i.e 18.28, 12.08 and 7.87% of the total population, respectively. There was no IAA producing rhizobacteria population was found in karamunting rhizosphere. Based on the results of the ability of the test to produce IAA in the King’s B liquid medium at low pH (pH 4.0), the leading isolates were obtained in each rhizosphere, namely: J.2b and J.3b isolates from maize rhizosphere; Kc.1b, Kc.2b and Kc.3b from peanut isolates, and Ti.3c isolates from titonia rhizosphere.Key words : Rhizobacteria, IAA, Rhodomyrtus tomentosa, Tithonia diversifolia, peanut and maize

Colonization of peanut roots by biofilm-forming Paenibacillus polymyxa initiates biocontrol against crown rot disease

To investigate the role of biofilm-forming Paenibacillus polymyxa strains in controlling crown root rot disease. Two plant growth-promoting P. polymyxa strains were isolated from the peanut rhizosphere, from Aspergillus niger-suppressive soils. The strains were tested, under greenhouse and field conditions for inhibition of the crown root rot pathogen of the peanut, as well as for biofilm formation in the peanut rhizosphere. The strains' colonization and biofilm formation were further studied on roots of the model plant Arabidopsis thaliana and with solid surface assays. Their crown root rot inhibition performance was studied in field and pot experiments. The strains' ability to form biofilms in gnotobiotic and soil systems was studied employing scanning electron microscope. Both strains were able to suppress the pathogen but the superior biofilm former offers significantly better protection against crown rot. The study highlights the importance of efficient rhizosphere colonization and biofilm formation in biocontrol.

Growth, nitrogen fixation, yield and kernel quality of peanut in response to lime, organic and inorganic fertilizer levels

The aim of this investigation was to study the effect of different levels of chemical fertilizers alone and in combination with farmyard manure and lime on growth, nitrogen fixation, yield and kernel quality of peanut in an acid lateritic soil. Five fertilization levels viz., no chemical fertilizer (CF) (F 0), CF @ 20:40:30 (F 1), CF @ 40:80:60 (F 2) kg ha −1 NPK, F 1 + 2.5 t ha −1 FYM (F 3) and F 2+5 t ha −1 FYM (F 4) with and without liming (2 t ha −1) were tested. Results revealed that integrated application of FYM + CF at F 3 level significantly ( P ⩽ 0.05) improved the nitrogen content of nodules (12.4%), kernel yield (19.3%), mineral composition, oil content (4.8%), protein content (28.2%) and hydration coefficient (11.6%) of kernels over sole CF at F 1 level. Maximum level of CF or FYM + CF though improved the population of symbiotic nitrogen fixing bacteria in the peanut rhizosphere, however, could not improve nitrogen fixation, yield and kernel quality.

Bicarbonate concentration as affected by soil water content controls iron nutrition of peanut plants in a calcareous soil

Strategy I peanut plants are frequently subjected to iron deficiency when growing in calcareous soils, which contain high concentrations of bicarbonate. In calcareous soils under field conditions, it has been noted that chlorosis increases in severity after excessive rainfall or irrigation, but the chlorosis symptoms of peanuts are alleviated after waterlogged soils dry. A pot experiment was conducted simulating the chlorosis symptom observed in the field when peanut plants are exposed to fluctuating soil water content induced from rainfall or irrigation. We investigated the bicarbonate fluctuations resulting from adjustable soil water content (SWC) that could lead to bicarbonate-induced iron chlorosis of peanuts growing in calcareous soil. The experiments included three treatments of SWC (50% of water holding capacity (WHC), 80% of WHC, and 100% of WHC) under two levels of CaCO 3 concentrations (at 8.67% and 18.67%.) The results showed that the iron nutrition of peanuts could be regulated by different SWC at both CaCO 3 levels. Our observations indicate that iron deficiency chlorosis symptoms in peanuts grown in high soil water content were more severe, compared to those of peanuts in lower soil water content. A shift from high soil water content to lower soil water content could improve or eliminate the iron deficiency chlorosis symptom of peanuts. The HCO 3 − concentration in the peanut rhizosphere increased with increasing SWC and CaCO 3 content and it correlated with the level of soil water content. We suggest that variations in the soil water content could induce HCO 3 − concentration variation in the rhizosphere of peanuts. Consequently, the high HCO 3 − concentration, which is induced by a high water content in calcareous soil and a high CaCO 3 level, could inhibit the physiological response to iron deficiency of peanuts, resulting in iron deficiency chlorosis. The study indicates that a reasonable agricultural practice of irrigation and drainage should be considered to improve and prevent iron deficiency chlorosis of strategy I plants in calcareous soil.

Incidence and Potential Host-Plant Resistance of Peanut (Arachis hypogaea L.) to Plant Parasitic Nematodes in Southern Ghana, West Africa

Abstract A survey was conducted during 1999 and 2001 in Ashanti, Brong Ahafo, Eastern, and Volta regions of Ghana, West Africa, to identify nematode pests of peanut (Arachis hypogaea L.). Information from the survey is being used to formulate appropriate integrated pest management (IPM) strategies for peanut production in these regions. Ten genera of plant parasitic nematodes belonging to three Orders were identified. Population density and distribution of genera varied in the four peanut-growing regions. Six genera, Helicotylenchus, Meloidogyne (juveniles), Paratrichodorus, Pratylenchus, Rotylenchulus, and Xiphinema were found in all four regions. Hoplolaimus was found only in the Eastern region. Trichodorus and Tylenchorhynchus were absent from Ashanti and Brong Ahafo regions but present in Eastern and Volta regions. Nematode genus Rhignema of the Order Rhigonematida was isolated from millipedes sampled from the rhizosphere of peanut. Twenty-one peanut cultivars and experimental lines were assembled fro...

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.

A study on the improvement iron nutrition of peanut intercropping with maize on nitrogen fixation at early stages of growth of peanut on a calcareous soil

A glasshouse study employing a split-root technique was conducted to investigate the influence of intercropping with maize (Zea mays L.) in a calcareous soil on N2 fixation by peanut (Arachis hypogaea L.) at early stages of growth. In this intercropping system, competitive interactions between maize and peanut for N and improvement of Fe uptake were likely to be important factors affecting N2 fixation of peanut. The experiment was comprised of three treatments which included treatment I: peanut monocropping; treatment II: maize/peanut intercropping (the major and the minor compartments with low N, 50 mg kg−1); treatment III: maize/peanut intercropping (the major compartment with low N, 50 mg kg−1 and the minor compartment with high, N 200 mg kg−1). The minor compartment of treatment III was fertilized with 200 mg kg−1 N for reducing or eliminating the competition of N coming from intercropping maize. Intercropping with maize corrected Fe chlorosis of peanut by significantly increasing plant Fe concentration and uptake. Compared with the monocropping treatment, iron uptake increased from intercropping treatment II and III by 22 and 24% per plant, 30 and 29% shoots, 38 and 60% nodules. Iron uptake by the root nodules was especially enhanced in the intercropping system. In contrast, intercropping with maize had little effect on NO3 −1-N concentrations in the soil rhizosphere of peanut or on N concentrations and uptake by peanut compared with plants in monoculture. The results indicate that the improvement in Fe nutrition was an important factor promoting N2 fixation by peanut in the intercropping system at the flowering stage of peanut growth, and that competition for N by intercropped maize had little effect on N2 fixation by peanut under the experimental conditions.

Iron Availability as Affected by Soil Moisture in Intercropped Peanut and Maize

Pot and rhizobox experiments were carried out to investigate the iron availability in intercropped peanut and maize as affected by soil moisture. Results from pot experiment showed that the root growth of peanuts were significantly inhibited at 25% soil water content compared to those at 15% soil water content. The chlorophyll content in the new leaves of intercropped peanut decreased and leaves became chlorotic at 25% soil water content. There were no significant differences in the active iron concentration in new leaves of peanut between 15% and 25% soil water content. The soil pH were higher in peanut rhizosphere than in bulk soil at the early, middle, and harvest stages for both 15% and 25% soil water content. The soil bicarbonate content was also higher in peanut rhizosphere than in bulk soil for both 15% and 25% soil water content. There was significant difference in soil bicarbonate of peanut rhizosphere between 15% and 25% soil water content at the harvest stage. The available iron content in both rhizosphere soil and bulk soil were lower than 3.5 mg kg−1 in all growth stages at both 15% and 25% soil water content. Results from rhizobox experiment showed that citric acid, maleic acid, and fumaric acid in exudates of peanuts significantly increased at 25% soil water content compared to that at 15% soil water content. The apoplastic iron content of peanut roots decreased by 0.216 and 0.409 µmol g−1 fresh weight−1 (FW) from the 28th growth day to 42nd growth day at 25% and 15% soil water content, respectively. The mobilizing ability of apoplastic iron in intercropped peanuts at 15% soil water content was 20.1% higher compared to that at 25% soil water content. It is concluded that improvement of iron nutrition of peanuts with intercropping with maize could be affected by soil moisture condition.

Iron Nutrition of Peanut Enhanced by Mixed Cropping with Maize: Possible Role of Root Morphology and Rhizosphere Microflora

Field observations have indicated that Fe deficiency chlorosis symptoms in peanut are more severe and widespread in monoculture than intercropped with maize in calcareous soils of northern China. Here we report a pot experiment that investigated the mechanisms underlying the marked improvement in Fe nutrition of peanut grown in mixture with maize. Iron deficiency chlorosis occurred in the young leaves of peanut in monoculture and was particularly obvious at the flowering stage, while the young leaves of peanut grown in mixture with maize remained green throughout the experiment. The chlorophyll and HCl‐extractable Fe concentrations in young leaves of peanut grown in mixture were much higher than those in monoculture, indicating that maize may have markedly improved the peanut Fe nutrition. Growth in mixture was associated with greatly altered root morphology and microbial populations in the rhizosphere of peanut. Visual observation of peanut roots in monoculture showed that they were larger in diameter and shorter than those in mixture. Moreover, peanut roots in mixture with maize produced more lateral roots and had increased root length compared with plants in monoculture. Peanut grown together with maize showed obvious rhizodermal transfer cells in the subapical root zone, but cells with cell wall ingrowths were poorly developed in peanut in monoculture. Mixed culture resulted in a significantly decreased abundance of bacteria in the rhizosphere of peanut compared with monoculture, and electron microscope observations indicated that this was associated with a thicker mucigel layer on the root surface of peanut in mixture with maize. Several root morphological and rhizosphere microbial factors may thus have contributed to the improvement in Fe nutrition of peanut in mixed culture.

Survival of Bacillus subtilis AF 1 in the bacterized peanut rhizosphere and its influence on native microflora and seedling growth

A mutant of Bacillus subtilis AF 1 (an antifungal strain with plant growth-promoting activity, resistant to 100 μg streptomycin/ml) was isolated from pigeon pea rhizosphere and, when used in peanut bacterization, decreased fungal and bacterial numbers and increased the actinomycete population in the rhizosphere. Over 28 days, AF 1 declined by 0.9 log c.f.u. in sterilized soil and by 2.6 log c.f.u. in native soil. From the seedlings raised with peanut seeds bacterized with AF 1 at 6.5 log c.f.u./seed, 4.1 and 4.7 log c.f.u. of AF 1 were recovered from the rhizosphere and total underground parts, respectively. Bacterization with AF 1 had no significant growth-promoting or -inhibiting effect on the peanut.

The Genera Basiria Siddiqi, 1959, Neopsilenchus Thorne & Malek, 1968 and Filenchus Andrássy, 1954 (Nematoda: Tylenchidae) From Cameroon, With a Description of Basiria Paratumida N. Sp

A new species of the genus Basiria Siddiqi, 1959 is described from the rhizosphere of peanut, Arachis hypogaea L. in Ndop, North West Province, Cameroon. B. paratumida n. sp. is characterised by its well-developed, anteriorly-situated median bulb, dorsal oesophageal gland outlet about 2.5 μm posterior to stylet base, a V' value of 75-79%, a tail/V-A value of 0.6-0.7, and a tail distinctly striated along its entire length with a rounded terminus. The new species resembles B. duplexa (Hagemeyer & Allen, 1952) Geraert, 1968 and B. tumida (Colbran, 1960) Geraert, 1968. From B. duplexa, it is distinguished by its shorter body, shorter oesophagus, and shorter, striated tail with a rounded terminus. It differs from B. tumida in its lower V' value, its greater vulva-anus distance and its striated tail which also relates it to B. graminophila Siddiqi, 1959 from which it is distinguished by its more anteriorly-situated median bulb and dorsal oesophageal gland outlet. Morphometric data, descriptions, and illustrations of four known tylenchs, namely, Basiria graminophila; B. tumida; Neopsilenchus minor (Geraert, 1968) Kheiri, 1972; and Filenchus aquilonius (Wu, 1969) Siddiqi, 1986, all recorded for the first time in Cameroon, are given as well as hosts and localities of occurrence.

Comparative identification by fatty acid analysis of soil, rhizosphere, and geocarposphere bacteria of peanut (Arachis hypogaea L.)

Bacterial isolates were collected from the geocarposphere, rhizosphere, and root-free soil of field grown peanut (Arachis hypogaea L.) at three sample dates, and the isolates were identified by analysis of fatty acid methyl-esters to determine if qualitative differences exist among the bacterial microflora of these zones. Five bacterial genera were associated with isolates from soil, while pod and root isolates constituted 16 and 13 genera, respectively, indicating that bacterial diversity was higher in the rhizosphere and geocarposphere than in soil. The dominant (most frequently identified) genus across all three samples dates was Flavobacterium, for pods, Pseudomonas for roots, and Bacillus, for root-free soil. Sixteen bacterial taxa were only isolated from the geocarposphere, 7 only from the rhizosphere, and 5 only from soil. These results show that specific bacterial taxa are preferentially adapted to colonization of the geocarposphere and suggest that the soil, rhizosphere, and geocarposphere constitute three distinct ecological niches. Bacteria which colonize the geocarposphere should be examined as potential biological control agents for pod-invading fungi such as the toxigenic strains of Aspergillus flavus and A. parasiticus.

Rhizosphere colonization by Serratia marcescens for the control of Sclerotium rolfsii

Two-hundred and three different strains of bacteria were isolated from the rhizosphere of bean, peanut and chickpea plants grown in Sclerotium rolfsii infested soil. A bacterium, identified as Serratia marcescens, was found to be the best biocontrol agent of the pathogen, under greenhouse conditions (up to 75% disease reduction). Populations of 10 5 or 10 6 CFU g −1 soil were the most effective in disease control. The drench and drip application of S. marcescens suspension were more effective in controlling S. rolfsii than spraying, mixing in soil or seed coating. This bacterium significantly reduced damping-off incidence of bean, caused by Rhizoctonia solani, by 50%, but was not effective against Pythium aphanidematum in cucumber. A natural mutant of S. marcescens, resistant to the antibiotic rifampicin, was isolated. The mutant, effective as the wild type, was used to study rhizosphere colonization. The highest population density of the bacteria was found on the proximal portion of the root, decreasing significantly until the tips, where they increased again.

Fungal populations in the rhizosphere of peanut (Arachis hypogaea L.)

A comparison of fungal populations in the rhizospheres of eight varieties of peanut grown in a red lateritic soil amended with farmyard manure was made by the dilution-plate technique. There was a marked increase in fungi in the rhizospheres of TMV 2, TMV 4, Pollachi Red and EC 1698, the increase was smaller in Spanish Improved and RS 1 while very little rhizosphere effect was shown by TMV 3 and Pondicherry 8. Age of the plant had a significant influence on numbers of fungi in the rhizosphere. High R/S ratios were obtained when the plants were 30 days old, at which time attained maximum vegetative growth and started to flower. The ratios gradually decreased after that age until the plants were three months old when there was again a small increase. This later rise in fungal populations is interpreted to be due to an increase in microbial activity around dead or senescent roots. No correlation could be established between numbers of root nodules produced by a variety and its rhizosphere effect. Preferential stimulation of certain fungi in the rhizosphere of some of the varieties was noticed.