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.     

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.     

Optimum Level of Nitrogen and Phosphorus to Achieve Better Papaya (Carica papaya var. Solo) Seedlings Growth and Mycorrhizal Colonization

An experiment under greenhouse conditions was carried out to evaluate the best level of nitrogen (N) and phosphorus (P), which promote the growth of papaya (Carica papaya L. var. Solo) seedlings without affecting the arbuscular mycorrhizal fungi (AMF) activity. Seedlings of papaya were transplanted to pots inoculated or not with Gigaspora margarita spores at four levels of N (0, 50, 100, and 200 ppm) and P (0, 25, 50, and 100 ppm). P was amended at the same time of pot filling up with substrate but N was applied weekly. The experiment was harvested after 100 days and plant dry weight together with AMF colonization was measured. The major response on the plant dry weight and height was from the fertilizers (N and P) where it proportionally increased. For the dry weight, at low amounts of nutrients the effects of AMF were greater, but as much as the fertilizer level in soil increased this response decreased. The colonization decreased as the nutrient levels increased, especially the P. The best combination of N and P for plant growth and AMF colonization could be at 50 and 25 ppm, equivalent to 5 and 2.5 kg/10a, respectively.     

Arbuscular mycorrhizal inoculation of micropropagated persimmon plantlets

Summary

Growth, development and nutrient status of micropropagated persimmon (Diospyros kaki) ‘Rojo Brillante’ in response to inoculation with two species of arbuscular mycorrhizal (AM) fungi were studied under nursery conditions. The species of AM fungi were Glomus intraradices and G. mosseae. Shoot growth depression and low root colonization percentage were observed to G. mosseae inoculation. Shoot and root growth enhancements were observed for plants colonised by G. intraradices. Inoculated plantlets with G. intraradices and high level of controlled-release fertilizer signi®cantly decreased shoot height in relation to treatment with low fertilization level. Furthermore, G. intraradices had unique effects on the mineral status of the persimmon plantlets. N and Ca were significantly increased and decreased, respectively, within the shoot tissue of plants colonised by G. intraradices. Early inoculation with G. intraradices appears to favour growth of micropropagated persimmon plantlets.     

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.     

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.     

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.     

三种丛枝菌根真菌对辣椒根系生长的影响及效应分析

以辣椒品种金塔为试材,播种时分别接种3种丛枝菌根真菌菌剂(G.etunicatum、G.mosseae、G.versiforme),菌根化育苗后定植,研究辣椒生长发育过程中根系的生长及酶活性变化。结果表明:3种丛枝菌根处理的根系生物量,根系活力,根系SOD、POD、CAT活性及产量均明显高于对照。3个供试菌种中,G.mosseae对辣椒根系的促生效应表现最佳。     

Mycorrhizal colonization improves onion (Allium cepa L.) yield and water use efficiency under water deficit condition

Most plants benefit from mycorrhizal symbiosis through improvement of water status and nutrient uptake. A factorial experiment with complete randomized blocks design was carried out in greenhouse at Tabriz University, Iran in 2005–2006. Experimental treatments were (a) irrigation interval (7, 9 and 11 days), (b) soil condition (sterile and non-sterile) and (c) arbuscular mycorrhizal fungi (AMF) species (Glomus versiforme, Glomus intraradices, Glomus etunicatum) and non-mycorrhizal (NM) plants as control. Onion (Allium cepa L. cv. Azar-shahr) seeds were sown in sterile nursery and inoculated with fungi species. One nursery left uninoculated as control. Nine weeks old seedlings then were transplanted to the pots. Average pre-irrigation soil water contents reached to about 67, 61.6 and 57.5% of FC corresponding to 7, 9 and 11 days irrigation intervals, respectively. At onion bulb maturity stage (192 days after transplanting), yield, water use efficiency (WUE) and yield response factor (K_y) were determined. The results indicated that AMF colonization increased soil water depletion significantly. G. versiforme under both soil conditions (sterile and non-sterile) and G. etunicatum in sterile soil depleted soil water effectively (P < 0.05). Mycorrhizal fungi improved WUE significantly (P < 0.0001) in both soil conditions. It raised by G. versiforme about 2.4-fold (0.289 g mm⁻¹) in comparison with the control (0.117 g mm⁻¹). G. intraradices and G. etunicatum also had significantly higher WUE than control. Apparently water deficit in 11-day irrigation interval led to lower yield and WUE compared to 9-day interval; the later resulted highest WUE (0.254 g mm⁻¹). Mycorrhizal plants increased seasonal ET significantly due to enhancing in plant growth; G. versiforme in both sterile and non-sterile soil and G. etunicatum in sterile soil had the highest ET. Bulb yield was influenced by irrigation period and fungi species. G. versiforme produced higher yield than other treatments (135.27 g/pot). Mycorrhizal plants in 11-day irrigation interval in spite of suffering from water stress had more bulb yield than non-mycorrhizal plants in all irrigation intervals. Yield in general was higher in 9-day treatments than other irrigating internals significantly (P < 0.05). Onion yield response factor (K_y) was decreased by AMF colonization; implying that symbiosed plants become less responsive to water deficit (longer irrigation interval) compared to the control ones.     

Role of bioinoculants in development of salt-resistant saplings of Morus alba (var. sujanpuri) in vivo

Pot experiments were conducted for the development of salt-resistant saplings of Morus alba (var. sujanpuri) involving bioinoculants, namely arbuscular mycorrhizal (AM) fungi, Azotobacter and indole butyric acid (IBA). The IBA and sodium chloride (NaCl) concentrations were optimized prior to the experiments. By using both low and high concentrations, 15 ppm IBA and 0.05% NaCl (w/v) were found to be optimum in acting synergistically with AM fungi and Azotobacter and also for increasing all the growth parameters and microbial count in the rhizosphere. For in vivo development of salt-resistant saplings, the optimal concentration of IBA, along with AM fungi and Azotobacter in different combinations, was applied. The saplings were irrigated regularly with 0.05% NaCl water. Although growth parameters such as AM infection percentage, AM spores per 100 g soil and Azotobacter cells/g soil were affected by NaCl watering, the inoculation of both bioinoculants significantly enhanced survival percentage of saplings from 25 to 50% under salt stress. Maximum survival (55%) of saplings was found with IBA (15 ppm)+AM fungi+Azotobacter.     

Changes in free amino acid concentrations in mycorrhizal strawberry plants

The influence of arbuscular mycorrhizal fungi (AMF) colonization on free amino acid concentrations in strawberry (Fragaria × ananassa Duch., cv.Nohime) plants was investigated using two AMF species [Glomus mosseae (Gm), Gl. aggregatum (Ga)] under phosphorus-supplemented (+P) or non-supplemented (−P) conditions. Ten weeks after AMF inoculation, mycorrhizal plants showed higher values in dry weight of both shoots and roots than did non-mycorrhizal ones among most of the treatments. Shoots and roots of mycorrhizal plants had greater phosphorus concentrations in −P plots, while in +P plots, P concentrations differed little among the inoculation treatments. AMF colonization was greater in plants inoculated with Gm than in plants inoculated with Ga. Total amino acid concentration was higher in most of the plants inoculated with Gm than in non-mycorrhizal ones regardless of P treatment. Serine, glutamic acid, glycine, alanine, leucine and GABA were higher in both mycorrhizal plants in −P plots than in non-inoculated plants. In +P plots, threonine and isoleucine concentrations were greater in both mycorrhizal plants than in non-inoculated ones. Asparagine, glutamic acid, glycine, citrulline, GABA and arginine were greater in plants inoculated with Gm than in non-mycorrhizal ones. These findings verified that inoculation with AMF increases total amino acid concentrations and concentrations of specific amino acids in strawberry plants with or without phosphorus supplementation, though the effects varied with species of mycorrhizal fungus.     

Effects of applications of plant growth regulators to papaya on the output and proteolytic activity of latex tapped from immature fruits

SUMMARY

Pistillate seedling plants of the local cultivar of papaya ‘Deshi’, transplanted 40 d after sowing, were sprayed with aqueous solutions of IBA (25 and 50 _ppm), GA₃ (100 and 200 _ppm), kinetin (50 and 100 _ppm), BA (25 and 50 _ppm), ethephon (100 and 200 ppm) or with water (control) 100 d after transplanting, when the experimental fruits borne by them were 15 d old. Latex was collected from the fruits when they were 90-95 d old and continued on four occasions, at 7 d intervals. Highly significant increases in yield and in protease activity of the latex over the control was obtained by application of ethephon. IBA and GA, also increased latex production, but spraying the plants with kinetin or BA solutions gave no clear results     

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.     

Soil pasteurization and inoculation with Glomus intraradices alters flower production and bulb composition of Zephyranthes spp.

Summary

We assessed whether adding inoculum of the vesicular-arbuscular mycorrhizal fungus (VAMF) Glomus intraradices into growing medium of three Zephyranthes spp (White Rain Lily [WRL], Z. candida; Pink Fairy Lily [PFL], Z. robusta; Yellow Zephyr Lily [YZL], Z. sulphurea) alters aspects of flower and bulb production. Shoots of inoculated plants emerged 7–13 d earlier than those of non-inoculated plants. Inoculation slightly delayed the emergence of flower buds on WRL and PFL, but did not delay the time of flower opening of WRL. Inoculated YZL flowered 4–11.d earlier than non-inoculated plants. The number of flowers produced by YZL was consistently increased by inoculation, while the inoculation with VAMF increased flower production by WRL and PFL only when plants were growing in pasteurized soil. Leaf biomass of inoculated WRL was larger than non-inoculated plants, while leaf biomass was generally smaller in inoculated PFL and YZL. Partitioning of biomass to bulbs and offsets varied with species, soil pasteurization, and inoculation. Inoculation increased the combined weight of bulbs and offsets at the end of the second growing cycle by 50–150%. Inoculated YZL and WRL consistently produced more offsets in the second growing season after inoculation. For all species, inoculation increased phosphorus and carbohydrates and decreased nitrogen and amino acids in bulbs. Adding VAMF into the growing medium of Zephyranthes altered aspects of plant development and biomass partitioning important to flower and bulb production during the first growing cycle after inoculation, and most effects of VAMF inoculation are more pronounced in the second growing cycle after inoculation. Of the three species examined, Z. sulphurea showed the most consistent responses to inoculation.     

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。     

Use of organic agricultural wastes as growing media for the production of Anthurium andraeanum ‘Pink Lady’

Summary

The conventional organic growing medium used for anthurium (Anthurium andraeanum) production is peat. Quality peat, however, is costly and is a non-renewable natural resource. The current study compared the suitability of using charred and composted organic agricultural wastes (OAW) vs. sphagnum peat as components of various growth media for the ornamental plant, anthurium (A. andraeanum ‘Pink Lady’). Ten different media were prepared from composted corn cobs (C), charred corn cobs (CC), charred garden waste (CG), and Pindstrup? sphagnum peat moss (P) in various proportions. The media contained [on a % (v/v) basis]: C (100%), CC (100%), CG (100%), C (70%) + CG (30%), CC (70%) + CG (30%), C (35%) + CG (15%) + P (50%), CC (50%) + P (50%), CC (35%) + CG (15%) + P (50%), C (50%) + P (50%), or P (100%) as a control. After 15 months in a greenhouse, the growth and flowering of transplanted anthurium plants were optimal using P, CC+P, or CC+CG+P.These results indicate that mixing charred OAW with peat could provide a suitable medium for anthurium production, thereby reducing the need for peat and converting agricultural waste material into useful products.     

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.     

Arbuscular mycorrhizal fungi alleviate iron deficient chlorosis in Poncirus trifoliata L. Raf under calcium bicarbonate stress

Summary

The effect of the arbuscular mycorrhizal (AM) fungus Glomus versiforme on chlorosis due to iron deficiency in trifoliate orange (Poncirus trifoliata L. Raf) was studied under calcium bicarbonate stress in sand culture. Seeds were sown in a mixed substrate [1:1 (v/v), perlite:sand] with or without mycorrhizal inoculum. The test was carried out with four treatments: Hoagland and Arnon nutrient solution with normal, no added iron, or 50% normal iron at two levels of calcium bicarbonate. The results showed that the proportion of the total root length infected by the AM fungus was ≥ 83%, and was depressed under Fe deficiency. No root colonisation was found with no added AM fungus (NM plants).

Colonisation by AM fungus resulted in higher dry weights of both shoots and roots compared to NM treatments, suggesting that the AM fungus accelerated plant growth. The activities of peroxidase and catalase in NM plants were lower than in AM fungus-inoculated plants. The results indicate that AM fungus alleviated calcium bicarbonate stress on the cell membranes of host plants. The results also showed that AM fungus increased chlorophyll concentrations, iron contents, and the Fe:P ratios of whole plants, and decreased 50(10P+K):Fe ratios, which implied that the uptake and translocation of iron was strengthened. Therefore, AM fungus had a positive effect on ameliorating chlorosis due to iron deficiency in P. trifoliata L. Raf.     

Mannitol-producing tobacco exposed to varying levels of water,light, temperature and paraquat

Summary

Transgenic mannitol-producing (+mtlD) and wild-type (–mtlD) tobacco plants were exposed to water deficit, varying light intensities, low temperatures, and paraquat applications to test whether mannitol was involved in protection against abiotic stresses. In the water deficit experiment, –mtlD and +mtlD plants were fully irrigated [100% evapotranspiration (ET)] or received 25% ET for 40 d. Water deficit reduced the relative water content (RWC) of both types of plant, starting on day 22, and the total stem length (TSL) of –mtlD 25% ET plants after 11 d, whereas the TSL of +mtlD 25% ET plants was reduced only after 34 d. After 30 d of water deficit, a higher percentage of mature foliage was retained by +mtlD 25% ET plants compared to –mtlD 25% ET plants. The mannitol-1-phosphate dehydrogenase activity of +mtlD plants was not affected by water deficit. The photosynthetic rates of +mtlD and –mtlD plants were measured at PPFD levels ranging from 0 to >2,000 μmol m^–2 s^–1. No differences in quantum yield, saturation and compensation points, or dark respiration were observed between the +mtlD and –mtlD plants. Exposing the leaves of +mtlD and –mtlD plants to 0°C for 24 h caused significant injury to cell membranes and was similar in both types of plant. The application of 0.2 mM paraquat onto expanding –mtlD leaves produced a higher percentage of necrotic leaf area (4.3%) compared to +mtlD leaves (0.48%). The amount of mannitol produced by +mtlD plants could not provide significant osmotic protection, or increases in photosynthesis, whereas it may provide a specific system to protect cells from free radical-induced damage.     

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.