Inoculation of root microorganisms for sustainable wheat-rice and wheat-black gram rotations in India

The scarcity of non-renewable resources such as soils and fertilizers and the consequences of climate change can dramatically influence the food security of future generations. Mutualistic root microorganisms such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) can improve plant fitness. We tested the growth response of wheat (Triticum aestivum [L.]), rice (Oriza sativa [L.]) and black gram (Vigna mungo [L.], Hepper) to an inoculation of AMF and PGPR alone or in combination over two years at seven locations in a region extending from the Himalayan foothills to the Indo-Gangetic plain. The AMF applied consisted of a consortium of different strains, the PGPR of two fluorescent Pseudomonas strains (Pseudomonas jessenii, R62; Pseudomonas synxantha, R81), derived from wheat rhizosphere from one test region. We found that dual inoculation of wheat with PGPR and AMF increased grain yield by 41% as compared to un-inoculated controls. Yield responses to the inoculants were highest at locations with previously low yields. AMF or PGPR alone augmented wheat grain yield by 29% and 31%, respectively. The bio-inoculants were effective both at Zero and at farmers’ practice fertilization level (70 kg N ha⁻¹, 11 kg P ha⁻¹ in mineral form to wheat crop). Also raw protein (nitrogen × 5.7) and mineral nutrient concentration of wheat grains (phosphorus, potassium, copper, iron, zinc, manganese) were higher after inoculation (+6% to +53%). Phosphorus use efficiency of wheat grains [kg P grain kg⁻¹ P fertilizer] was increased by 95%. AMF and PGPR application also improved soil quality as indicated by increased soil enzyme activities of alkaline and acid phosphatase, urease and dehydrogenase. Effects on rice and black gram yields were far less pronounced over two cropping seasons, suggesting that AMF and PGPR isolated from the target crop were more efficient. We conclude that mutualistic root microorganisms have a high potential for contributing to food security and for improving nutrition status in southern countries, while safeguarding natural resources such as P stocks.     

Potential of earthworms,ants, millipedes,and termites for dissemination of vesicular-arbuscular mycorrhizal fungi in soil

We studied the effects of earthworms, termites, ants, and millipedes on the dissemination of vesciulararbuscular mycorrhizal (VAM) propagules. Earthworm (Lumbricus terrestris L.) casts collected from the garden were air-dried, stored, and examined for the presence of VAM fungi by inoculating the cast material onto onion plants grown in sterilized soil. VAM propagules survived for a period of 12 months. The results showed that earth-worms can contribute to the dissemination of VAM propagules. Nests of ants (Camponotus compressus Fabr.) collected from different locations were examined for the presence of VAM propagules. They harboured up to 790 infective propagules g^-1 of nest, showing that ants can be potential vectors in disseminating VAM fungi. The faecal pellets of the millipede (Phyllogonostreptus nigrolabiatus Newport) collected from the rearing tank were tested for VAM colonization. Though VAM propagules were present in the fresh faecal pellets, they lost their viability after 4 days of storage. Termitaria samples of both mound-building and subterranean termites were also examined for VAM propagules but those found were non-viable.     

Effect of cropping sequence,fertilizers and farmyard manure on vesicular-arbuscular mycorrhizal fungi in different crops over three consecutive seasons

Summary The influence of cropping sequence with and without fertilizer and farmyard manure application on vesicular-arbuscular mycorrhizae was studied over three consecutive seasons. In the first season maize was grown on all the plots. In the second season cowpea, groundnut and finger millet were raised on the same plots and in the third season, sunflower was grown on all the plots. The groundnut grown in the second season stimulated mycorrhizal root colonization, sporulation and infective propagules in the soil, and these effects were carried over to the next season. The plots cropped to finger millet in the second season had the lowest number of mycorrhizal spores. The application of farmyard manure stimulated vesicular-arbuscular mycorrhizae while fertilizers at the recommended level decreased the mycorrhizal propagules.     

Nutrient acquisition and nitrate reductase activity of mycorrhizal Retama sphaerocarpa L. seedlings afforested in an amended semiarid soil under two water regimes

Abstract. We studied the effect of inoculation with three arbuscular-mycorrhizal (AM) fungi ( Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge) and Glomus mosseae ([Nicol & Gerd.] Gerd. & Trappe) and the addition of composted sewage sludge on root nitrate reductase (NR, EC 1.6.6.1.) activity, mycorrhizal colonization, plant growth and nutrient uptake in Retama sphaerocarpa L. seedlings afforested in a semiarid, degraded Mediterranean soil under well-watered and non-watered conditions. Six months after planting, the mycorrhizal inoculation and the irrigation of plants had a strong effect on the growth parameters. The effect on plant growth was a negative interaction between plant irrigation and mycorrhizal inoculation and a positive interaction between plant irrigation and composted sewage sludge addition. The latter treatment had a significant, but moderate, effect on the growth but conferred no additional benefit when combined with mycorrhizal inoculation. Mycorrhizal inoculation, composted sewage sludge and irrigation had a significant effect on NR activity in roots and on foliar nutrients. The irrigation significantly increased the positive effect of composted sewage sludge on NR activity and the concentrations of foliar N and K. The effect of mycorrhizal inoculation on NR activity did not depend on the water regime. The effectiveness of mycorrhizal inoculation on the establishment and growth of R. sphaerocarpa seedlings in these Mediterranean conditions was independent of water regime. The addition of composted sewage sludge was only effective when soil water was freely available. The combination of mycorrhizal inoculation and composted sewage sludge addition had no synergistic effect on plant growth.     

Response of Mycorrhiza-Inoculated Pepper and Amino Acids to Salt Treatment at Different Ratios

Mycorrhiza has attracted interest as one of the microorganisms that increase a crop’s salt stress tolerance. This study was conducted to determine the impacts of mycorrhiza inoculation and applying salt at different ratios on the yield of peppers and amino acid concentrations. The study was conducted in greenhouse conditions on loamy soils with four salt treatments, two mycorrhiza inoculations and a control in a complete randomized block design. The present study indicated that salt treatment alone was significantly correlated with crop stem and root amino acid concentrations, RWC% and leaf sizes, whereas applying mycorrhiza showed a positive relationship to stem height, stem and root wet weight, and root amino acids but led to a decloine in root serine and glutamine, and stem amino acid and glutamine. In conclusion, inoculating with mycorrhiza was observed to make a positive contribution to salt stress tolerance at different levels in almost all the parameters examined.     

Mango explant browning: Effect of ontogenic age,mycorrhization and pre-treatments

The in vitro performance of mango shoot culture is delimited by several factors, of which explant necrosis and media browning are considered as major constraints for successful exploitation of such an important commercial crop. Our results showed that source of explants had a significant effect on the performance of in vitro cultures of mango. The variations in survival of explants collected from glasshouse grown seedlings and field-grown stock plants indicated towards differences between their physiological/ontogenic age. Though, chronologically, both are young, the glasshouse grown shoots are ontogenetically younger and; therefore, responded better over field-grown shoots. Improved performance of explants harvested from mycorrhizal plants suggests integration of mycorrhizal biotechnology with tissue culture biotechnology in order to achieve better results as mycorrhiza being a well-known stress alleviator may help explants mitigate in vitro stresses. Furthermore, shoot tip explants of field-grown ‘Amrapali’ mango was assayed for their browning propensity at pre- and post-culture stages. Status of different bio-chemicals such as in vivo phenol, in vitro phenol exudation, phenylalanine ammonia lyase, peroxidase and polyphenol oxidase as affected by various pre-treatments were estimated to establish the relationship of these bio-chemicals with necrosis of mango shoot cultures. The different pre-treatments comprised etiolation of newly emerged shoots (5–7 days old) of stock plants using black polythene for 7 days, etiolation treatment + agitation of explants in antioxidant solution (antioxidants: ascorbic acid at 100 mg l⁻¹ + citric acid at 50 mg l⁻¹), etiolation treatment + agitation of explants in polyvinylpyrrolidone solution (PVP) at 0.2% and non-etiolated control. Of these, explants treated with PVP proved to be superior to other treatments with regards to explant necrosis percentage as such explants exhibited least activities of phenols and oxidative enzymes. Correlation studies indicated existence of high positive correlation between explant necrosis and these bio-chemicals.     

Tree girdling provides insight on the role of labile carbon in nitrogen partitioning between soil microorganisms and adult European beech

Nitrogen (N) cycling in terrestrial ecosystems is complex since it involves the closely interwoven processes of both N uptake by plants and microbial turnover of a variety of N metabolites. Major interactions between plants and microorganisms involve competition for the same N species, provision of plant nutrients by microorganisms and labile carbon (C) supply to microorganisms by plants via root exudation. Despite these close links between microbial N metabolism and plant N uptake, only a few studies have tried to overcome isolated views of plant N acquisition or microbial N fluxes. In this study we studied competitive patterns of N fluxes in a mountainous beech forest ecosystem between both plants and microorganisms by reducing rhizodeposition by tree girdling. Besides labile C and N pools in soil, we investigated total microbial biomass in soil, microbial N turnover (N mineralization, nitrification, denitrification, microbial immobilization) as well as microbial community structure using denitrifiers and mycorrhizal fungi as model organisms for important functional groups. Furthermore, plant uptake of organic and inorganic N and N metabolite profiles in roots were determined.Surprisingly plants preferred organic N over inorganic N and nitrate (NO₃⁻) over ammonium (NH₄⁺) in all treatments. Microbial N turnover and microbial biomass were in general negatively correlated to plant N acquisition and plant N pools, thus indicating strong competition for N between plants and free living microorganisms. The abundance of the dominant mycorrhizal fungi Cenococcum geophilum was negatively correlated to total soil microbial biomass but positively correlated to glutamine uptake by beech and amino acid concentration in fine roots indicating a significant role of this mycorrhizal fungus in the acquisition of organic N by beech. Tree girdling in general resulted in a decrease of dissolved organic carbon and total microbial biomass in soil while the abundance of C. geophilum remained unaffected, and N uptake by plants was increased. Overall, the girdling-induced decline of rhizodeposition altered the competitive balance of N partitioning in favour of beech and its most abundant mycorrhizal symbiont and at the expense of heterotrophic N turnover by free living microorganisms in soil. Similar to tree girdling, drought periods followed by intensive drying/rewetting events seemed to have favoured N acquisition by plants at the expense of free living microorganisms.     

铁皮石斛菌根真菌对铁皮石斛组培苗的接种效应

[目的]对铁皮石斛（Dendrobium officinale）菌根真菌对铁皮石斛组培苗的接种效应进行研究。[方法]以从野生铁皮石斛根系中分离得到的Tjl、Tj2、Tj3真菌为材料,将其接种到铁皮石斛组培苗的根系上进行接种试验。[结果]在组培条件下,Tjl菌在前期没有表现出促生作用,Tj2菌表现出较强的促生作用,Tj3菌则对根具有促生作用,而在后期,Tj1菌则表现出了较强的促生作用,Tj2菌的接种效果最好,促生作用最强,Tj3菌则出现烂根烂苗现象;在室外条件下,Tj2菌接种使组培苗叶数增加,侧芽数增加,侧根生长明显,株高增加显著,叶片大而深绿,根部有明显的膨大现象。[结论]2种接种方式均说明Tj2菌对铁皮石斛的地上植株和地下根系生长,株数增多,株高增加,新芽和新根萌发均具有较强的促进作用,证明Tj2菌与铁皮石斛有效地建立了共生关系。因此Tj2菌对石斛组培苗的成功栽培具有实际应用价值。     

菌根菌对煤矸石环境的作用

在总结煤矸石改良的相关成果基础上,综述了菌根菌对煤矸石环境的影响的研究成果,并提出了尚需进一步深入研究的问题和建议。     

Improved Nutrient Uptake and Growth of Maize in Response to Inoculation with Thiobacillus and Mycorrhiza on an Alkaline Soil

Most plant nutrients are optimally available when soil pH is close to neutral. In this experiment the effects of Thiobacillus and Mycorrhiza on nutrient uptake and grain yield of maize were studied on an alkaline soil as a factorial experiment with randomized complete blocks design. Treatments consisted of Mycorrhiza fungi (M): inoculated (m₁) and noninoculated (m₀), Thiobacillus (T): inoculated (t₁) and noninoculated (t₀), and sulfur (S) (S₀, S₁: 250, and S₂: 500 kg ha^?1). Inoculation of Mycorrhiza, Thiobacillus, and S application decreased soil pH and increased grain yield and seed oil content. The lowest soil pH and the greatest S content were obtained from the combination of Thiobacillus and 500 kg ha^?1 S. Inoculation of Thiobacillus and S application significantly decreased root colonization. The greatest iron (Fe) content was in the combination of Mycorrhiza inoculation and 500 kg ha^?1 S. Grain P content significantly increased with Mycorrhiza inoculation and S application. The greatest grain yield obtained from combination of Thiobacillus with 500 kg ha^?1 S.