Effect of mycorrhizal inoculation and soluble phosphorus fertilizer on growth and phosphorus uptake of pearl millet

Summary Six mycorrhizal fungi were tested as inoculants for pearl millet (Pennisetum americanum Leeke) grown in pots maintained in a greenhouse. VAM fungi varied in their ability to stimulate plant growth and phosphorus uptake. Inoculation withGigaspora margarita, G. calospora andGlomus fasciculatum increased shoot drymatter 1.3 fold over uninoculated control. In another pot trial, inoculation withGigaspora calospora andGlomus fasciculatum resulted in dry matter and phosphorus uptake equivalent to that produced by adding phosphorus at 8 kg/ha.The influence of inoculatingGigaspora calospora on pearl millet at different levels of phosphorus fertilizer (0 to 60 kg P/ha) as triple superphosphate in sterile and unsterile alfisol soil was also studied. In sterile soil, mycorrhizal inoculation increased dry matter and phosphorus uptake at levels less than 20 kg/ha. At higher P levels the mycorrhizal effect was decreased. These studies performed in sterilized soil suggest that inoculation of pearl millet with efficient VAM fungi could be extremely useful in P deficient soils. However, its practical utility depends on screening and isolation of fungal strains which perform efficiently in natural (unsterilized) field conditions.     

Dual inoculation with VA mycorrhiza and Rhizobium is beneficial to Leucaena

Summary Response ofLeucanea leucocephala to inoculation withGlomus fasciculatum and/or Rhizobium was studied in a phosphorus deficient unsterile soil.G. fasciculatum only inoculation improved nodulation by native rhizobia and Rhizobium only treatment improved colonization of roots by native mycorrhizal fungi. Dual inoculation with both the organisms improved nodulation, mycorrhizal colonization, dry weight, nitrogen and phosphorus content of the plants compared to single inoculation with either organism. Contribution of U.A.S. Research Project DR/AMB-1.     

Dual inoculation withRhizobium sp. andGlomus fasciculatum enhances nodulation,yield and nitrogen fixation in chickpea (Cicer arietinum Linn.)

Summary Seed inoculation with Rhizobium and soil inoculation withGlomus fasciculatum increased nodulation, nitrogen and phosphorus concentration in plants and yield of chickpea (Cicer arietinum) var. BG 212 in pots containing unsterilized soil especially with 50kgP₂O₅ ha⁻¹ in the form of superphosphate. Inoculation with Rhizobium orG. fasciculatum separately or in combination significantly increased the N₂ fixed in straw and grain than uninoculated controls as determined by¹⁵N atom percent excess of plants grown in soil amended with labelled ammonium sulphate (¹⁵NH₄)₂SO₄) at the rate of 20kg N ha⁻¹. These increases were most pronounced when P was applied at 50kgP₂O₅ ha⁻¹.     

Field response of chickpea to inoculation withGlomus versiforme

The response ofCicer arietinum to inoculation withGlomus versiforme under field conditions was investigated in a phosphorus deficient sandy loam soil. Inoculation with the mycorrhizal fungusGlomus versiforme increased the rate of VAM development in chickpea. The weight of nodules and the number of nodules per plant were higher in inoculated than in uninoculated plants. The phosphorus content of the shoots and its total uptake, were increased by either the application of single super-phosphate, or by inoculation withG. versiforme. Inoculation increased shoot dry weights and grain yields by 12% and 25% respectively, as compared with the 33% and 60% increases respectively produced by P-treated plants.     

Growth and nutrient uptake of peanut inoculated with the mycorrhizal fungusGlomus fasciculatum compared with non-inoculated ones

Summary In a greenhouse study, inoculation with the mycorrhizal fungusGlomus fasciculatum enhanced peanut growth and increased its dry matter more than 2-fold compared with the non-inoculated control, in both sterilized and non-sterilized soil. It also significantly increased uptake of phosphorus and micronutrients such as zinc, copper, manganese and iron.Present address: International Crops Research Institute for the semi-arid tropics (ICRIAST), Patancheru 502 324, A.P. India.     

Growth of three legume trees inoculated with VA mycorrhizal fungi and Rhizobium

Effectiveness among four VA mycorrhizal fungi and Rhizobium (R) in promoting growth of three legume trees in a P-deficient soil was studied.Glomus fasciculatus + R andGigaspora margarita + R were most effective forAcacia mangium andAlbizia falcataria (syn.:Paraserianthes falcataria). Scutellospora persica + R,Gigaspora margarita + R andGlomus fasciculatus + R were most effective forAcacia auriculifornis. Consistently poor growth was attained by seedlings inoculated withSclerocystis clavispora + R,Rhizobium alone, or by uninoculated seedlings.     

Influence of phosphorus level on VA Mycorrhizal colonization and growth of cowpea cultivars

Vesicular-arbuscular mycorrhizal (VAM) associations often vary according to the abundance of available soil phosphorus (P). Therefore, understanding the response of crop plants to colonization by VAM fungi necessitates the study of the response of colonized and noncolonized plants, from a range of cultivars, to differing levels of P. Cowpea is grown throughout the world, often on impoverished soils in which it can benefit from formation of mycorrhizae. The present study was conducted to determine the response of four cultivars of cowpea (Vigna unguiculata (L.) Walp.), varying in nitrogen fixation capacity, to inoculation withGlomus fasciculatum at four levels of added P in the rooting medium. In a greenhouse experiment, four cowpea cultivars, Mississippi Silver, Brown Crowder, Six Week Browneye and MI 35, were grown with and without the mycorrhizal fungus at four levels of added P, 0, 10, 20 and 30 ppm. Root colonization (%) was negatively correlated with P content of the growth medium and shoot P concentration. Intraspecific variability was shown for shoot dry weight and leaf area in response to inoculation withG. fasciculatum at different P levels. The range of P required in the growth medium which allowed benefit fromG. fasciculatum was identified for individual cultivars using shoot dry weight and leaf area, and collectively across cultivars for other parameters.     

Mycorrhizal inoculation in neem (Azadirachta indica) enhances azadirachtin content in seed kernels

In view of the high mycorrhizal dependency of neem trees (Azadirachta indica), an experiment was conducted to study if Arbuscular Mycorrhizal (AM) inoculation can enhance the azadirachtin content in seed kernels of trees grown in the field. Azadirachtin is an important active ingredient in neem seed kernels based on which a large biopesticide industry has emerged in India and few countries in Europe and the USA. Inoculation of neem seedlings in the nursery with Glomus fasciculatum and Glomus mosseae resulted in increased height, dry weight, root colonization and phosphorus (P) content. In a separate experiment, field-grown neem plants inoculated in the nursery and during transplantation with Glomus fasciculatum were evaluated after 5 years. No significant differences were found in the tree height, girth at breast height (GBH) and fruit yield but oil percentage, total triterpenoids and azadirachtin content in kernels increased significantly as a result of AM inoculation. A similar enhancement in azadirachtin was noted with P application. These results open up possibilities of producing quality neem seed with high bioactive ingredients through AM inoculation.     

Effect of vesicular-arbuscular mycorrhizal and phosphatase-producing fungal inoculation on growth and nutrition of white clover supplied with organic phosphorus

In a pot experiment white clover was grown for 50 d in two sterilized low phosphorus soils supplied with organic phosphorus as sodium phytate. Seed inoculation withAspergillus fumigatus, a phosphatase-producing fungus (PPF), and soil inoculation withGlomus mossece, a vesicular-arbuscular mycorrhizal (VAM) fungus resulted in increased shoot and root dry mass and root length, phosphatase activity in soil and shoot concentrations of P and to a lesser extent of Mg. The effects on these parameters were most distinct upon combined inoculation treatment (PPF+VAM). A significant increase in hyphal length density and decrease in Mn concentration was observed only upon PPF+VAM treatment. Shoot concentrations of Cu and Zn were highly enhanced by VAM but not by PPF. Of the total P uptake the PPF contribution accounted for 39–41 %, VAM contributed 41–50 % and their combination resulted in 55–58 %, in comparison to only 38–40 % contribution due to soil microorganisms under unsterilized conditions. The depletion of organic phosphorus in the rhizosphere soil increased in the order (PPF+VAM)>VAM>PPF> unsterilized soil>sterilized soil. The results demonstrate the efficient use of phytate phosphorus byA. fumigatus andG. mosseœ and suggest that dual inoculation is superior to a single one.     

Influence of soil pH on the soybean-endomycorrhiza symbiosis

Summary Soybean (Glycine max {L.} Merr.) cultivars were inoculated withGigaspora gigantea andGlomus mosseae to determine mycorrhizal: cultivar relationships as affected by soil pH. The specific cultivarfungal response was dependent on soil pH. Overall cultivar responses in unlimed soil (pH 5.1) were greater forG. gigantea thanG. mosseae. The Bossier —G. gigantea combination was particularly responsive in unlimed soil and showed an increase of 10% in shoot length, 35% in shoot dry weight. 75% in root dry weight, and 397% in nodule dry weight over uninoculated controls. Little cultivar response was observed withG. mosseae inoculation in unlimed soil. In limed soil (pH 6.2), the larger responses were obtained withG. mosseae inoculated plants, although inoculation with eitherG. mosseae orG. gigantea appeared effective. In general, nodulation was greater on mycorrhizal roots than on control roots.     

Growth stimulation ofTamarindus indica by selected VA mycorrhizal fungi

Efficient vesicular arbuscular mycorrhizal (VAM) fungi were screened and selected for a slow-growing forest tree species,Tamarindus indica L., important in tropical forestry. Seedlings were inoculated with 13 different VAM fungi, obtained from various sources around the world. Inoculated plants had greater plant height, leaf number, stem girth, biomass, phosphate and Zn²⁺ content. They also had higher amounts of mycorrhizal spores, per cent root colonization and external hyphae, as measured by per cent soil aggregation.Tamarindus indica seedlings responded best to inoculation withGigaspora margarita (ICRISAT) followed byGlomus fasciculatum.

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Résumé On a testé et sélectionné des moisissures mycorrhizales (VAM) vésiculaires, arbusculaires efficaces pour une espèce d'arbre forestier à croissance lente,Tamarindus indica L., importante en foresterie tropicale. On a inoculé des semences avec 13 moisissures VAM différentes, obtenues de diverses sources de par le monde. Les plants inoculés sont plus hauts, ont un nombre de feuilles et une circonférence de tronc plus élevés et un contenu plus élevé en biomasse, phosphate et Zn²⁺. Ils ont aussi une quantité plus élevée de spores mycorrhizales, une colonisation d'un pourcentage plus élevé de racines et d'hyphes externes, mesurés par le pourcentage d'aggrégation du sol. Les semences deTamarindus indica répondent le mieux à l'inoculation deGigaspora margarita ICRISAT suivi de celle deGlomus fasciculatum.

     

Effect of native and introduced arbuscular mycorrhizal fungi on growth and nutrient uptake ofLygeum spartum andAnthyllis cytisoides

The interaction between native and introduced fungi and their effect on plant growth and mineral uptake were studied. The host plants wereLygeum spartum andAnthyllis cytisoides, the introduced fungus wasGlomus fasciculatum. The four soils used were selected from disturbed and contaminated by mining activities areas. Inoculated and uninoculated plants were grown in the unsterilized and sterilized soils (with and withouth native microflora, respectively). Plants inoculated withG. fasciculatum were higher and had higher tissue P concentration than uninoculated plants, especially inA. cytisoides. However, this inoculation was not effective in unsterilized substrates, suggesting a competition between introduced and native fungi. Concentration of mineral elements other than P varied depending on the host plant and soil. Decrease in Fe, Cu, Mn, Zn and Pb was observed in mycorrhizalA. cytiosides plants and a slight increase in Zn concentration was noted in mycorrhizalL. spartum plants. The study showed that the type of soil and their populations of native endophytes have a considerable effect on plant response to mycorrhizal symbiosis, especially in disturbed soils.     

Effect of inoculation withGlomus mosseae on nitrogen fixation by field grown soybeans

Summary This field study was undertaken to determine the effect of inoculation withGlomus mosseae on N₂ fixation and P uptake by soybean. The inoculation withGlomus mosseae was achieved using a new type of inoculant, alginate-entrapped (AE) endomycorrhizal fungus. N₂ fixation was assessed using the A value method. In P-fertilized plots, inoculation with AEGlomus mosseae increased the harvest index based on dry weight (+20%) and N content of seeds (+17%), the A value (+31%) and %N derived from fixation (+75%). Inoculation with AEGlomus mosseae decreased the coefficient of variation for the A value and for the dry weights of the different plant parts.     

Symbiotic effectiveness of Hup+ Rhizobium,VAM fungi and phosphorus levels in relation to nitrogen fixation and plant growth ofCajanus cajan

Effect of hydrogen uptake positive (Hup⁺) strain ofRhizobium sp. (pigeon pea) and VAM fungus (Glomus fasciculatum) was studied on the symbiotic parameters of pigeon pea (Cajanus cajan) cv. AL-15 at various levels of phosphorus. The Hup⁺ Rhizobium strain showed more nodulation, plant biomass and plant nitrogen content than its Hup⁻ counterpart. VAM infection in pigeon pea roots helped in translocating phosphorus from the soil and improved nitrogen fixation. Similarly, addition of phosphorus was found to play a positive role in enhancing all these parameters. Dual inoculation of Hup⁺ Rhizobium strain and VAM significantly increased nodulation, nitrogenase activity, plant nitrogen and phosphorus content and plant biomass compared to single inoculation of either organism and dual inoculation with Hup⁻ and VAM fungus.     

Response of Sesbania grandiflora to Inoculation of Soil with Vesicular-Arbuscular Mycorrhizal Fungi

A greenhouse experiment was conducted to determine the influence of two tropical isolates of Glomus fasciculatum and Glomus mosseae on the nutrient uptake and growth of Sesbania grandiflora. Inoculation of sterile soil with the fungi significantly improved growth and nutrient uptake by S. grandiflora, but the response of the legume was markedly better when the soil was inoculated with G. fasciculatum than when it was inoculated with G. mosseae. Nutrient uptake and growth of S. grandiflora in nonsterile soil was also significantly stimulated by inoculation, but the legume did not respond differently to the two endophytes under this condition.     

Effects of phosphate fertilization,lime amendments and inoculation with VA-mycorrhizal fungi on soybeans in an acid soil

Soybeans [Glycine max (L.) Merr. cv. Essex] were grown in nonsterile acid (pH. 5.2) infertile Wynnville silt loam (Glossic Fragiudult) in a glasshouse. The effects of P fertilization and lime were determined by inoculation with two VAM-fungi (VAMF): Glomus fasciculatum (Gf) and Glomus etunicatum (Ge). An important factor affected by the interaction between applied lime (soil acidity), applied P, and VAMF inoculation was the soil Al. Five application rates of P as KH₂PO₄ and three rates of lime were tested. Potassium was equalized with KCl (muriate of potash). P-efficiency (g seed/mg P kg^-1 soil) by vesicular-arbuscular mycorrhiza (VAM) was maximal at 20 mg P kg^-1 soil at all lime and VAMF treatments. VAMF inoculation increased plant survival and protected the soybeans from leaf scorch, thereby substituting for the effects of lime and P. The Ge inoculum was superior in ameliorating leaf scorch in the nonlimed soil. The Gf inoculum required more lime and P than the Ge inoculum to increase seed yield relative to the noninoculated controls containing only native VAMF. Both inocula increased root Al uptake and extractable soil Al in the acid soil without apparent adverse effects on root or shoot. The ability of the VAMF inocula to enhance the efficiency of applied P and decrease seed Cl concentration was increased by lime. Seed yield (Y) was negatively related to seed Cl concentration (X) where Y=aX^-b. Both VAMF inoculation and lime application reduced this negative relationship and may have increased the tolerance to both Cl and soil Al.     

Glomus macrocarpum: a potential bioinoculant to improve essential oil quality and concentration in Dill (Anethum graveolens L.) and Carum (Trachyspermum ammi (Linn.) Sprague)

The effects of application of two arbuscular mycorrhizal (AM) fungi Glomus macrocarpum and G. fasciculatum on shoot biomass and concentration of essential oil in Anethum graveolens L. and Trachyspermum ammi (Linn.) Sprague fruits were evaluated. Results revealed significant variation in effectiveness of the two AM fungal species. AM fungal inoculation in general improved the growth of the plants. On mycorrhization, the concentration of essential oil increased up to 90% in dill and 72% in carum over their respective controls. Glomus macrocarpum was more effective than G. fasciculatum in enhancing the oil concentration. The constituents of the essential oils were characterized by gas liquid chromatography. The levels of limonene and carvone were enhanced in essential oil obtained from G. macrocarpum-inoculated dill plants, while G. fasciculatum inoculation resulted in a higher level of thymol in carum.     

Intracellular Burkholderia strain has no negative effect on the symbiotic efficiency of the arbuscular mycorrhizal fungus Gigaspora margarita

This study investigates the effects of bacteria occurring in thecytoplasm of some arbuscular mycorrhizal fungi (AMF) on their symbioticefficiency. Gigaspora margarita, Gigasporarosea and Glomus versiforme, containing orwithout intracellular bacteria, were compared for their efficiency instimulating growth of Lactuca sativa L. Biomass productionand nutrient contents were evaluated in plants grown on two substrates. Theefficiency of G. margarita harbouring a homogenouspopulation of Burkholderia was greater than that of theother two AMF, mainly G. rosea, which does not containintracellular bacteria. When plants were grown in poor soil, inoculation withG. margarita resulted in the best growth rates as well asthe highest N, P and K values. The significantly higher N content is ofparticular importance, since the genome of Burkholderiapossesses nif genes.     

Response of lentil to VA Mycorrhizal inoculation and plant available P levels of unsterile soils

Summary Responses of lentil in unsterile soils at low, medium and high levels of plant available soil P toGlomus fasciculatum inoculation were evaluated. It was observed that growth, dry matter accumulation, nodulation, and nitrogen fixation were considerably improved in VAM inoculated plants over uninoculated control at low and medium levels of plant available soil P.     

Association between N2-fixing bacteria and pearl millet plants: Responses,mechanisms and persistence

Responses to inoculation with N₂-fixing bacteria were studied in relation to genotypic differences in pearl millet, effect of nitrogen levels, and FYM additions in India. In some experiments, inoculation increased mean grain yield up to 33% over the uninoculated control, whereas in the remaining 11 experiments there was no significant increase. Increased grain yields, >10% over the uninoculated controls were observed in 46% of the experiments withAzospirillum lipoferum (18.7% average increase) and withAzotobacter chroococcum (13.6% average increase). Yield increases were nil or reduced in three experiments withAzos. lipoferum and four experiments withAztb. chroococcum. In two experiments continued inoculation for two or three years resulted in increased grain, plant biomass yield, and N uptake. Interactions of bacterial cultures with cultivars or years were not observed. The counts of the inoculated strains increased two to three-fold when inoculation was continued for three years. Repeated inoculations increased the mean cumulative N uptake from season 1 to season 3 by 19 kg ha^–1. Repeated inoculations withAztb. chroococcum andAzos. lipoferum increased mean grain yield of a succeeding crop by 14.4% and 9.8%, respectively, over the uninoculated control. Inoculation increased the efficiency of N-assimilation by pearl millet. Marginal increase in nitrogenase activity, associated with the inoculated plants was observed during later stages of plant growth. Increased leaf nitrate reductase activity (NRA) was observed after inoculation with these bacteria. The responses to inoculation are mainly attributable to increased plant N assimilation which could be the effect of growth promoting substances secreated by the bacteria; and thus the contribution from BNF may be small.CRISAT, journal article 732.