In vitro culture of arbuscular mycorrhizal fungi: advances and future prospects

Arbuscular mycorrhizal (AM) fungi are ecologically important for most vascular plants for their growth and survival. AM fungi are obligate symbionts. In recent years, there have been many attempts to cultivate in vitro. Some relevant results indicate efforts are not far from successful growth of AM fungi independent of a plant host. This paper describes the methods to cultivate root organs, and to select and purify AM fungal inocula (intraradical and extraradical forms). Axenic and monoxenic cultures of AM fungi are summarized and we propose a methodology to recover and achieve continuous culture of AM fungi without lost of infectivity. The in vitro systems have proved to be a valuable tool to study fundamental and practical aspects of AM symbiosis, complementing the in vivo experimental approaches. Finally, we give some proposals of in vitro AM researches to exploit more the potentialities of AM symbiosis. Key words: Arbuscular mycorrhizal fungi, continuous culture, root organ cultures, intraradical and extraradical forms, in vitro. African Journal of Biotechnology Vol. 2 (12), pp. 692-697, December 200

Solanum cultivar responses to arbuscular mycorrhizal fungi: growth and mineral status

A greenhouse experiment was carried out in a sandy soil with a low available phosphorus to evaluate responsiveness of four Solanum aethiopicum cultivars to indigenous arbuscular mycorrhizal fungi. Results showed clear interaction between genetic variability of cultivars and fungal isolates on shoot biomass and on mineral status. Arbuscular mycorrhizal fungi can be ranked as Glomus aggregatum > Glomus mosseae > Glomus versiforme for improving yield as well as nitrogen, phosphorus, and potassium acquisition of Solanum cultivars. Key words: Arbuscular mycorrhizal fungi, Solanum aethiopicum, sterile soil, relative mycorrhizal dependency. African Journal of Biotechnology Vol.2(11) 2003: 429-43

Study of the Effect of Pseudomonas Putida and Funneliformis Mosseae on the Growth and Productivity of Tomato (Solanum Lycopersicum L.) in Senegal

In Senegal, the Niayes zone plays an important role in the economy of the country. It is the main horticultural production area. Among the crops cultivated, tomato (Solanum lycopersicum L.) is the second place of horticultural crops. However, this crop is confronted with biotic and abiotic constraints leading to lower yields. Thus, the objective of this study is to evaluate the impact of beneficial microorganisms such as rhizobacteria from the group of fluorescent Pseudomonas (Pseudomonas putida) and arbuscular mycorrhizal fungi (Funeliformis mosseae) on the productivity of tomatoes. Soil samples were taken from the rhizosphere of tomato plants. The bacterial strains were isolated by the method of suspensions dilutions, and then seeded on King B medium. Their identification was carried out by using the MALDITOF mass spectrometer. In order to evaluate the effect of these microorganisms on productivity, an experiment was conducted in the field for three months. An experimental device with three randomize blocks was adopted with four block treatments: T (control), PS1 (Pseudomonas putida), Fm (Funneliformis mosseae) and PS1 + Fm. The results obtained showed that the inoculation of tomato plants with PS1 or in combination with Fm induced the best yields with values exceeding respectively 5 t / ha and 1.5 t / ha compared with non-inoculated plants. The yield reductions observed in the case of co-inoculation between Fm and PS1 compared with PS1 treatment alone would suggest an antagonistic effect. These strains of Pseudomonas putida constitute an alternative for the increase of tomato productivity in the Niayes zone

Germination Stage Screening of Mutants of Cowpea (Vigna unguiculata L. Walp) to Salinity Tolerance

To test the tolerance of cowpea mutants to salinity, cowpea wilds and mutants were subjected to 50, 100, 150, 200, and 250 mM NaCl to test for tolerance to salinity. Genotype and salt concentration interaction were significant. GxS explained mostly the variation observed. More informative salt concentrations were found in 50 mM (99.08) and C100 mM (72.50) against 26.80 in the control environment. High salt concentrations had the lowest germination rates. Seed germination rate of cowpea genotypes decreased from 56.46 to 20.58 with a mean of 36.28 and a variance of 99.08. Despite strong correlations observed between indices, very weak ones were found between AD and STI, -0.02, -0.44, -0.7, -0.79 and -0.84 respectively at salt concentration of 50, 100, 150, 200 and 250. Mouride wild types were most tolerant to salt with a germination rate of 43 % at 50 mM versus 48 and 551 % for respectively Melakh and Yacine. Six (6) mutants were more tolerant to the weakest checks performance which was the 9th best performance

Effet de la salinité sur la germination graines et la croissance des semis de treize cultivars africains de sésame (Sesamum indicum L.)

Le sésame (Sesamum indicum L.), une plante annuelle autoféconde originaire d’Afrique et d’Inde, est très sensible aux stades de germination et de semis mais modérément tolérant aux stress hydrique et salin. Cette étude menée en serre a pour objectif d’évaluer l’effet de différentes concentrations de NaCl sur la germination des graines et la croissance des semis de treize cultivars africains de sésame provenant du Sénégal, du Burkina Faso, du Cameroun et du Soudan. Un dispositif à blocs randomisés avec deux facteurs et trois répétitions a été utilisé . Les résultats montrent un effet négatif du gradient de salinité sur les taux de germination, de survie, la biomasse fraiche, la biomasse sèche, le diamètre au collet et la longueur de la tige. Les cultivars AS09, AS13, AS14, AS15, AS19 et AS25 ont été moins affectés par la salinité. L’importance de l’effet dépressif dépend de la concentration de sel et de la variété de cultivar de sésame. Sesame (Sesamum indicum L.), an annual self-pollinating plant native to Africa and India, is very sensitive to the stages of germination and sowing but moderately tolerant to water and salt stress. The objective of this greenhouse study is to assess the effect of different NaCl concentrations on seed germination and seedling growth of thirteen African sesame cultivars from Senegal, Burkina Faso, Cameroon and Sudan. A randomized block device with two factors and three replicates was used. The results show a negative effect of the salinity gradient on the germination rate, survival, fresh biomass, dry biomass, diameter at the collar and length of the stem. Cultivars AS09, AS13, AS14, AS15, AS19 and AS25 were less affected by salinity. The magnitude of the depressive effect depends on the concentration of salt and the sesame cultivar. &nbsp

Minireview - In vitro culture of arbuscular mycorrhizal fungi: advances and future prospects

Arbuscular mycorrhizal (AM) fungi are ecologically important for most vascular plants for their growth and survival. AM fungi are obligate symbionts. In recent years, there have been many attempts to cultivate in vitro. Some relevant results indicate efforts are not far from successful growth of AM fungi independent of a plant host. This paper describes the methods to cultivate root organs, and to select and purify AM fungal inocula (intraradical and extraradical forms). Axenic and monoxenic cultures of AM fungi are summarized and we propose a methodology to recover and achieve continuous culture of AM fungi without lost of infectivity. The in vitro systems have proved to be a valuable tool to study fundamental and practical aspects of AM symbiosis, complementing the in vivo experimental approaches. Finally, we give some proposals of in vitro AM researches to exploit more the potentialities of AM symbiosis

Mineral nutrition of mycorrhized tropical gum tree A. senegal (L.) under water deficiency conditions

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Arbuscular Mycorrhizal Fungi Improve Growth and Phosphate Nutrition of <i>Acacia seyal</i> (Delile) under Saline Conditions

Many plant species adapted to semi-arid environments are grown in the Sahelian region in northern Africa. One such species is Acacia seyal (Delile), a multipurpose leguminous tree grown in various agroecological zones, including saline soils. These challenging arid and semi-arid environments harbor a diversity of arbuscular mycorrhizal fungi (AMF) communities that can develop symbiotic associations with plants to improve their hydromineral nutrition. This study compared the effects of native AMF communities isolated from semi-arid sites (high, moderate, and low salinity zones Ndiafate, Ngane, and Bambey, respectively) and the AMF Rhizoglomus aggregatum on the development and phosphate nutrition of A. seyal seedlings subject to three salinity treatments (0, 340, and 680 mM). Plant height, dry matter weight of the shoots and roots, and phosphorus uptake from the soil were measured. Plants inoculated with AMF native species from each site that were provided with up to 340 mM of NaCl had greater shoot height than plants grown under 680 mM salinity. At NaCl concentrations above 340 mM, shoot and root development of A. seyal seedlings diminished. However, dry matter production of shoots (7%) and roots (15%) improved following AMF inoculation compared with the control (respectively 0.020 and 0.07 g for shoots and roots). When inoculated with AMF isolates from the high salinity zone (Ndiafate), phosphate content/nutrition was increased by 10% around 30 days after inoculation compared with non-inoculated seedlings (2.84 mg/kg of substrate). These results demonstrate that native AMF inoculants are capable of helping plants withstand environmental constraints, especially those exposing plants to harsh climatic conditions. We discuss insights on how AMF influences the interplay between soil phosphorus and perceived salinity that may have implications for broader relationships between plants and symbiotic fungi