Field response of papaya (Carica papaya L. cv. Coorg Honey Dew) to inoculation with arbuscular mycorrhizal fungi at different levels of phosphorus

Summary

Papaya (Carica papaya L.) cv. Coorg Honey Dew is one of the most popular cultivars grown in Southern India, but it requires high doses of inorganic phosphorus (P) fertilisation for growth. Arbuscular mycorrhizal fungi (AMF) are known to improve plant growth and nutrient uptake, especially the uptake of P and micronutrients. As papaya plants respond well to high levels of P, inoculation with AMF was studied to see if AMF could fulfill the requirement for P in plants grown under field conditions. Papaya seedlings (n = 36 per AMF) were colonised separately, in polybags, for 45 d by two species of AMF, Glomus mosseae and G. fasciculatum. Seedlings were then transplanted to the field, with uninoculated seedlings as controls, in a replicated randomised block design. Three levels of P were applied [50, 75, or 100% of the recommended dose (240 g plant^–1 year^–1) of P fertiliser, as super-phosphate]. Plants were studied for root colonisation by AMF, for growth parameters, and for leaf nutrient contents (especially, P, Zn, and Cu). Acidic and alkaline phosphatase activities in the roots of AMF-colonised plants were recorded as these enzymes are involved in the mobilisation of P. The yields of plants up to 18 months-old, and fruit quality, measured by total soluble solids contents (TSSC) and β-carotene contents, were recorded. AMF-inoculated plants performed better than uninoculated control plants at all levels of P applied. G. mosseae was more effective at improving plant growth, fruit yield, and P and Zn contents than G. fasciculatum at the 75% and 50% P-levels. Cu contents increased at all P-levels in G. fasciculatum-colonised plants. Total soluble solids contents showed marginal improvements at the 75% P level with both fungi. β-carotene contents increased significantly in G. mosseae-colonised plants at the 50% and 75% P-levels, and in G. fasciculatum-colonised plants at the 75% P-level. The feasibility of applying on-farm produced AMF inoculum to improve papaya cultivation and to save 25% of the P applied during papaya cultivation is discussed.     

Enhanced growth of micropropagated bulblets of Lilium sp. inoculated with arbuscular mycorrhizal fungi at different P fertility levels in an alfisol

Summary

The effect of three arbuscular mycorrhizal (AM) inocula at four available levels of phosphorus (8.41, 12.53, 13.63 and 14.6 ppm) in non-disinfected soil was studied on the growth, flowering, P uptake and root colonization in micropropagated bulblets of Lilium sp. (Asiatic hybrid ‘Gran Paradiso’). The inoculated bulblets fared significantly better than the uninoculated ones in terms of all the growth variables, namely size, weight, shoot length, number of leaves and leaf area, and in P uptake. However, bulblets inoculated with different AM inocula had optimum growth at different P levels. Bulblets inoculated with indigenous mixed vesicular-arbuscular mycorrhiza species (VAM I) and Glomus intraradices isolate 2 (VAM III) showed the best growth and early flowering at available soil P of 13.6 ppm, whereas those inoculated with Glomus intraradices isolate 1 (VAM II) showed higher growth at 2.5 ppm available soil P. Amongst the three tested inocula, VAM I promoted maximum shoot length, bulblet size, and weight at 13.6 ppm P. The bulblets under this treatment also flowered earlier, nearly a month before the uninoculated control ones.     

Screening mycorrhiza species for plant growth,P and Zn uptake in pepper seedling grown under greenhouse conditions

We screened the mycorrhizal species for an inoculum protocol would green pepper seedling production and compensate for nutrient deficiency. Three greenhouse studies (on three successive years) were conducted under nursery conditions using five arbuscular mycorrhizal (AM) fungi and their mixture. The AM fungi, Glomus mosseae, G. clarum, G. caledonium, G. intraradices and G. etunicatum propagated on maize roots were used. The AM fungi were inoculated to seed stages and half of the seed stages inoculated plants were re-inoculated at the seedling stages. In Experiment I, plants were harvested once and in Experiments II and III, plants were harvested twice at different developmental stages.     

Nursery inoculation of tomato with arbuscular mycorrhizal fungi and subsequent performance under irrigation with saline water

Protected horticultural crops as well as those planted in open fields particularly in the Mediterranean region have to cope with increasing salinization of irrigation water. High salinity of the supply water has detrimental effects on soil fertility and plant nutrition and reduces crop growth and yield. This study was conducted to determine if pre-inoculation of transplants with arbuscular mycorrhizal (AM) fungi alleviates salt effects on growth and yield of tomato (Lycopersicon esculentum Mill. Cv. Marriha) when irrigated with saline water. Tomato seeds were sown in polystyrene trays with 20 cm³ cells and treated with AM fungi (AM) or without (nonAM) Glomus mosseae. Once the seedlings were reached appropriate size, they were transplanted into nonsterile soil in concrete blocks (1.6 m × 3 m × 0.75 m) under greenhouse conditions. The soil electrical conductivity (EC_e) was 1.4 dS m⁻¹. Plants were irrigated with nonsaline water (EC_w = 0.5 dS m⁻¹) or saline water (EC_w = 2.4 dS m⁻¹) until harvest. These treatments resulted with soil EC at harvest 1.7 and 4.4 dS m⁻¹ for nonsaline and saline water treatments, respectively. Root colonization with AM fungi at flowering was lower under saline than nonsaline conditions. Pre-inoculated tomato plants with AM fungi irrigated with both saline and nonsaline water had greater shoot and root dry matter (DM) yield and fruit fresh yield than nonAM plants. The enhancement in fruit fresh yield due to AM fungi inoculation was 29% under nonsaline and 60% under saline water conditions. Shoot contents of P, K, Zn, Cu, and Fe were higher in AM compared with nonAM plants grown under nonsaline and saline water conditions. Shoot Na concentrations were lower in AM than nonAM plants grown under saline water conditions. Results indicate that pre-inoculation of tomato transplants with AM fungi improved yield and can help alleviate deleterious effects of salt stress on crop yield.     

The response of chilli (Capsicum annuum L.) plants to early inoculation with mycorrhizal fungi at different levels of phosphorus

Summary

Chilli plants cv. Pusa Jwala were inoculated in the nursery beds with three mycorrhizal fungi, Gigaspora calospora, G. margarita and Glomus fasciculatum and transplanted to plots supplied with 0, 25 and 50% of a recommended P level (65 kg ha^?1). Uninoculated plants were also transplanted at 0 (Control) and 100% of.the recommended P level. Plant growth, height, shoot dry weight, uptake of P, root colonization and yield of green chillies were measured. Chilli responded well to inoculation and P. G. margarita best improved growth and yield. Inoculation plus 25 and 50% P were equally better than the control and equal to uninoculated plants at 100% P. As much as 50–75% P can be dispensed with by inoculation with mycorrhizal fungi and this represents a considerable economic saving in cost.     

丛枝菌根真菌对香蕉试管苗植株生长和矿质营养吸收的影响

以Williams香蕉(MusaAAA)试管苗为材料,在温室盆栽条件下研究丛枝菌根真菌(AM真菌)对香蕉植株矿质营养和营养生长的影响。试验设3个处理,不接种对照和2个菌根接种处理:接种单一菌种Glomusversiform、接种混合菌种G.versiform、G.epigaeam、G.cadedonium。结果表明,香蕉植株的菌根侵染率为22.8%～32.9%;接种AM真菌促进了香蕉植株的营养生长,显著地增加地上部和根系的干重,其菌根依赖性达到30.8%～37.8%,植株的株高、叶片数和叶片长度略有提高;接种单一菌种增加了须根的数量,但2个接种处理均降低须根的长度,使得总根长减少;单一接种剂和混合接种剂分别显著提高植株的P和K含量,2个接种处理都显著地促进了植株对N、P、K的吸收,P增幅最大,为70%～120%,K的增幅次之,为80%左右,N的增幅最小,为40%～60%。结果还表明,混合接种剂的生长促进效果略好于单一接种剂。     

Vesicular-arbuscular mycorrhizal inoculation of micropropagated fruit trees

Micropropagated plantlets of OH x F 51 and GF 677, respectively pear (Pyrus communis L.) and peach (Prunus persica x Prunus amygdalus) clonal rootstocks were inoculated during an early weaning stage of acclimatization with Glomus sp. Both rootstocks were well colonized, although the infection of OH x F 51 spread more slowly. At the end of initial vegetative growth, mycorrhizal plants of both rootstocks showed a three-fold increase in shoot length over control plants. Mycorrhizal plants also had longer internode and greater fresh mass. The root/shoot ratio was especially altered by arbuscular mycorrhizal inoculation in OH x F 51 plants, which showed a greater increase in shoot rather than in root biomass. The growth-promoting ability of endomycorrhizal fungus persisted throughout the experimental period: Glomus sp. induced a greater development of both rootstocks in the second growing year, after overwintering. Colonization of micropropagated plants by arbuscular mycorrhizal fungus appears to alter the carbohydrate status in stems and roots. Mycorrhizal plants always had a higher content of total soluble sugar, although there were no differences in soluble carbohydrate concentration between inoculated and uninoculated plants. Starch accumulation was found only in mycorrhizal plants of the peach rootstock.     

Effect of arbuscular mycorrhizal fungi on growth,mineral nutrition,antioxidant enzymes activity and fruit yield of tomato grown under salinity stress

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by arbuscular mycorrhizal fungi Glomus mosseae. Tomato (Lycopersicon esculentum L. cv. Zhongzha105) plants were cultivated in soil with 0, 50 and 100 mM NaCl. Mycorrhization alleviated salt induced reduction of root colonization, growth, leaf area, chlorophyll content, fruit fresh weight and fruit yield. The concentrations of P and K were higher in AM compared with nonAM plants grown under nonsaline and saline conditions. Na concentration was lower in AM than nonAM plants grown under nonsaline and saline conditions. AMF colonization was accompanied by an enhancement of activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in leaves of both salt-affected and control plants. In addition, inoculation with AMF caused reduction in MDA content in comparison to salinized plants, indicating lower oxidative damage in the colonized plants.     

Isolation of arbuscular mycorrhizal fungi and Azotobacter chroococcum from local litchi orchards and evaluation of their activity in the air-layers system

Soil samples were collected from rhizosphere of litchi-growing areas of North-Western Himalayan Region (NWHR) of India, for finding qualitative and quantitative differences in arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum. These samples were taken from plants being grown in different cultivation types namely, weed control with weedicides or tillage; orchard floor either clear or with cover crops; intercropping with cereals and legumes. Qualitative and quantitative differences were noticed with different cultivation types and a marked reduction in the AM fungi was observed in orchards where chemicals were used for weed control and intensive farming system was used on the orchard floor. AM fungi were generally abundant in the soils with range pH 5.5–6.6. Among different AM fungi retrieved from the soils, Glomus spp. was most dominant. Fifteen AM fungal species were isolated, identified and characterized and along with their ability to colonize the roots. In the soil samples, a marked variation in viable bacterial count of A. chroococcum was also noticed due to varied physico-chemical characteristics of the orchard soils. The changes in AM fungal species composition can be attributed to changes in soil chemical properties resulting from cultural practices such as ploughing, application of chemical fertilizers and weedicides. An experiment was also conducted to study the comparative efficacy of four dominant and frequently occurring indigenous AM species namely, Glomus fasciculatum (Thaxter sensu Gerdemann), G. magnicaulis (Hall), G. mosseae (Nicol. & Gerd.), Gigaspora heterogamma (Nicol. & Gerd.) and two A. chroococcum strains viz., AZ₁ and AZ₂ singly and in dual combination to evaluate their effect in air-layers system. Dual inoculation of G. fasciculatum and AZ₁ increased total root length of air-layered shoots by 81.39% over uninoculated control. These studies indicated that indigenously isolated AM fungal species and A. chroococcum strains can be used for air-layering for better adaptation under specific agro-climatic and ecological zone conditions.     

Growth responses and endogenous IAA and iPAs changes of litchi (Litchi chinensis Sonn.) seedlings induced by arbuscular mycorrhizal fungal inoculation

Seedlings of litchi (Litchi chinensis Sonn.) were inoculated with two arbuscular mycorrhizal (AM) fungal species, Glomus intraradices and Gigaspora margarita. Plant growth response and morphological changes induced by AM inoculation were investigated. Plant endogenous indoleacetic acid (IAA) and isopentenyl adenosines (iPAs) concentrations were determined. With mycorrhizal infection rate of 9.0–18.8%, plant biomasses increased by 13.5–30.1%. Leaf number, leaflet number, total leaf area and first order lateral root number were significantly increased by AM inoculation. Although G. margarita significantly increased plant P content and uptake, no significant difference in N nutrition was observed between mycorrhizal and non-mycorrhizal plants. Enzyme-linked immunosorbent assay (ELISA) indicated the changes in IAA and iPAs induced by AM inoculation. IAA concentrations in shoots and in roots were 5–7 times and 2–5 times higher in mycorrhizal than in non-mycorrhizal plants, respectively. The iPAs concentrations increased by 1.7 times in shoots and by 1.9–2.5 times in roots, due to mycorrhizal inoculation. We suggest that the changes in endogenous phytohormone level may be responsible for morphological alteration induced by AM inoculation.     

Aptitude for mycorrhizal root colonization in Prunus rootstocks

Eighteen Prunus rootstock cultivars were inoculated with three arbuscular mycorrhizal fungi under greenhouse conditions in order to evaluate their affinity for mycorrhizal colonization. The rootstocks were peach–almond hybrids, peaches, plums and cherries of Spanish, French and Italian origin. Mycorrhizal colonization was low in plants inoculated with Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappe, and Glomus etunicatum Becker and Gerdemann. In contrast, Glomus intraradices Schenck and Smith, proved to be the most infective endophyte, achieving the highest mycorrhizal colonization rate in most of the rootstocks evaluated. Species of Prunus insititia L. were the only botanical group to show a consistently high affinity for mycorrhizal colonization with G. intraradices.     

Selection of efficient arbuscular mycorrhizal fungi in the rhizosphere of cashew and their application in the cashew nursery

Mycorrhizal association in cashew (Anacardium occidentale L.) grown in five different plantation areas of South India was investigated. The soil samples were collected from all locations. Physico-chemical properties of rhizosphere soils, arbuscular mycorrhizal fungal spore count and root colonization were recorded. Species isolated were Acaulospora, Gigaspora, Glomus and Scutellospora. The mycorrhizal spore density was maximum at Thanjavur and minimum at Kudumiyamalai. Root colonization percentage oscillated between 20 and 30%. The species of Glomus, G. aggregatum Schenck and Smith, G. fasciculatum (Thaxter) Gerdemann and Trappe and G. mosseae (Nicol. and Gerd.) Gerdemann and Trappe were the most abundant in the majority of the experimental sites. Hence these three species were selected and used for artificial inoculation studies. Of the three mycorrhizal fungi G. fasciculatum significantly increased shoot length, internode number, internode length, number of leaves, stem diameter, root length and root number.     

Determination of essential oil contents and micropropagation of Gaultheria fragrantissima,an endangered woody aromatic plant of India

Summary

Leaves of mature of Gaultheria fragrantissima Wall. plants (Indian wintergreen) were collected from various locations in the Eastern Himalayan region on the Indo-China border and were analysed by steam distillation and gas chromatography to identify an elite line that contained 1.79% (v/v) essential oils, 98% of which was methyl salicylate. Subsequently, a highly reproducible micropropagation protocol using adult shoot tips from this elite genotype was developed in order to conserve this highly-valued, endangered, woody oil-bearing aromatic shrub in India. Among several plant growth regulator (PGR) combinations tested for in vitro multiplication, up to 35 shoots per explant could be induced within 14 weeks of culture on woody plant medium (WPM) fortified only with 0.22 mg l^–1 thidiazuron (TDZ). These shoots could elongate on WPM containing 1.0 mg l^–1 kinetin. Rooted plantlets were acclimatised ex vivo, with 70% success. Random amplified polymorphic DNA (RAPD) analysis indicated the genetic uniformity of both the micropropagated plantlets and the donor plants. This is the first report on in vitro micropropagation of G. fragrantissima.     

丛枝菌根真菌对芋组织培养苗生长的影响

 于温室盆栽条件下研究了丛枝菌根(AM) 真菌Gigaspora rosea、Glomus mosseae 和Glomus versi-forme 对芋(Colocasia esculenta) 组织培养苗移栽成活率、矿质营养、光合速率及生长的影响。结果表明, 接种AM真菌能提高芋组织培养幼苗移栽成活率和叶片光合速率, 降低气孔阻力; 其叶片和根内氮、磷、钾含量和生长量显著高于不接种对照。认为接种有效AM真菌是促进组织培养苗健康生长的重要技术。     

In vitro micropropagation of Ephedra

The in vitro micropropagation of eleven species of Ephedra was investigated. Shoot nodal explants of E. fragilis were cultured on Murashige and Skoog medium supplemented with 3% sucrose, 0.05 jiM 3-indolebutryic acid and 0.0-0.5 |iM kinetin, zeatin or 6-ben- zylaminopurine. In general, the average number of shoots produced per explant increased and the average shoot length decreased with increasing cytokinin concentration. Substitution of 3-indolebutryic acid with 2,4-dichlorophenoxyacetic acid caused callusing and distorted shoot growth. Shoot cultures of ten other species were grown on 0.05 |iM 3-indolebutyric acid with 0.05 kinetin. Indole-3-acetic acid gave healthy rooting. E. equisitina, E. gerardiana, E. minima and E. saxatilis were successfully micropropagated using a single-stage protocol in which shoots were grown and rooted on Sorbarods using half strength Murashige and Skoog medium supplemented with 1% sucrose and 5.0 (iM indole-3-acetic acid. Healthy plantlets were weaned in John Innes No. 1: Perlite (1:1) following treatment with Captan (1.9 g I'1).     

Responses of field grown tomato plants to arbuscular mycorrhizal fungal colonization under varying intensities of drought stress

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck and Smith on growth, flower and fruit production, and fruit quality were studied in field-grown tomato plants exposed to varying intensities of drought stress. Inoculated (M+) and non-inoculated (M−) tomato seedlings were exposed to varying intensities of drought stress by adjusting irrigation intervals. Mycorrhizal plants had significantly higher uptake of N and P in both roots and shoots regardless of intensities of drought stress. AM inoculation also significantly increased shoot dry matter and the number of flowers and fruits. The fruit yields of M+ plants under severe, moderate, mild drought-stressed conditions were higher than M− plants by 24.7%, 23.1%, 16.2% and 12.3%, respectively. Furthermore, M+ plants produced tomato fruits that contain significantly higher quantities of ascorbic acid and total soluble solids (TSS) than M− plants. Mycorrhizal effects increased with increasing intensity of drought. The overall results suggest that mycorrhizal colonization affects host plant nutritional status, water stratus and growth under field conditions and thereby alters reproductive behaviour, fruit production and quality of fruits under both well-watered and drought-stressed conditions.     

Effect of arbuscular mycorrhizal fungi inoculation on aster yellows phytoplasma-infected tobacco plants

The objective of the research was to asses if arbuscular mycorrhizal fungi (AM) can modify the effect of two aster yellows phytoplasma strains infection in tobacco plants. Tobacco plants experimentally inoculated with aster yellows phytoplasma strains did not develop visible disease symptoms. However, PCR examination indicated that the inoculated plants were phytoplasma infected. Mycorrhiza inoculation had a positive effect on the shoot height of healthy plants, but did not influence shoot growth and weight of phytoplasma-infected plants. The roots of all mycorrhiza-inoculated plants were slightly reduced but significant differences were found in the total root length of plants infected with the phytoplasma strain AY1. AM inoculation had a positive effect on photosynthetic activity of tobacco plants infected with the phytoplasma strain AYSim, but net photosynthesis of tobacco infected with the phytoplasma strain AY1 was decreased. Transpiration rate and calcium content of AM and phytoplasma-infected plants were not affected. The mechanisms underlying these interactions are discussed and a direct action of the AM fungus is hypothesized.     

Responses of some different pepper (Capsicum annuum L.) genotypes to inoculation with two different arbuscular mycorrhizal fungi

Eight different pepper genotypes inoculated by two different arbuscular mycorrhizal fungi (AMF) [Glomus intraradices (Gi) and Gigaspora margarita (Gm)] in a growth chamber experiment under normal seedling growing conditions were evaluated for seedling traits, colonization and relative mycorrhizal dependency (RMD). In general, inoculated plants had greater dry weights compared to non-inoculated plants. Five cultivars responded positively to inoculation with AM fungi and three responded negatively. A great variation in mycorrhizal colonization dependency was observed among the pepper genotypes, with the N52 genotype showing the highest RMD and the Karaisali genotype the lowest. RMD and dry weights of pepper genotypes were inversely correlated.     

Pepper (Capsicum annuum L.) root growth and its relation to shoot growth in response to nitrogen

Summary

The main objective of this work was to investigate shoot and root morphology of pepper (Capsicum annuum L.) (cvs Early Calwonder, Keystone Resistant Giant, Jupiter, Shamrock and Gator Belle) grown in sand culture at three N-levels, 56,84 and 112 mg l^?1. Shoot, root, and root components were evaluated 40, 50 and 60 days after seeding. Tap, basal and lateral root accounted for 1%, 40% and 53%, respectively, of the total root dry weight. Shoot: root ratios did not differ between cultivars. Basal root length, basal root number and first-order lateral root number increased with increasing N. Cultivars with either long lateral roots or basal roots had short basal roots or lateral roots respectively, although only small differences were observed in other root and shoot characteristics. In this greenhouse environment, shoot/root ratio was constant. Nitrogen stimulated root and shoot growth, and this effect was significantly different for the root components.     

Monitoring the genetic fidelity of micropropagated plantlets of Spondias mangifera Willd. using RAPD marker assays

Summary

Random amplified polymorphic DNA (RAPD) markers were used to screen for clonal fidelity in in vitro-propagated plantlets of Spondias mangifera produced through direct organogenesis. One micropropagated plantlet was selected at random after each sub-cultural passage (six sub-cultures), along with the donor plant, for RAPD marker analysis. Twenty-five RAPD primers were used to study genetic similarities or dissimilarities with the mother plant as well as among the regenerated plants. Individual primers showed that the same pattern of RAPD markers was shared by all in vitro-propagated plantlets and the mother plant. No variation was observed among the micropropagated progenies. Thus, in vitro-regenerated plantlets of S. mangifera were clonally uniform and genetically stable.