Bernard F. Rodrigues

Arbuscular mycorrhizal status and root phosphatase activities in vegetative Carica papaya L. varieties

The arbuscular mycorrhizal (AM) status and root phosphatase activities were studied in four vegetative Carica papaya L. varieties viz., CO-1, CO-2, Honey Dew and Washington. Standard techniques were used to ascertain information on spore density and species diversity of AM fungi. Although in case of estimation of root colonization and root phosphatase activities, the existing methods were slightly modified. Root colonization and spore density of AM fungi along with root phosphatase (acid and alkaline) activities varied significantly in four papaya varieties. The present study recorded higher acid root phosphatase activity when compared with alkaline root phosphatase activity under P-deficient, acidic soil conditions. The present study revealed that the root colonization of AM fungi influenced acid root phosphatase activity positively and significantly under P-deficient, acidic soil conditions. A total of 11 species of AM fungi belonging to five genera viz., Acaulospora, Dentiscutata, Gigaspora, Glomus and Racocetra were recovered from the rhizosphere of four papaya varieties.

Biodiversity of Arbuscular Mycorrhizal （AM） fungi in mangroves of Goa in West India

Seventeen mangrove species of eight families at seven riverine and fringe habitats in Goa West India were surveyed for Arbuscular Mycorrhizal (AM) fungal diversity. Sixteen species were found to be mycorrhizal and one species showed no AM fungal colonization. AM root colonization was recorded at all seven sites and ranged from 6%–77%. Maximum root colonization was recorded in Excoecaria agallocha (77%) and minimum colonization in Avicennia marina (6%). Paris-type colonization was predominant at all sites. Auxiliary cells were recorded in roots of Acanthus ilicifolius, Ceriops tagal and Sonneretia alba. AM fungal root colonization and spore density varied by plant species and site. Site average spore density ranged from 1.84 spores·g−1 to 0.54 spores·g−1 of soil. In total, 28 AM fungal species of five genera, viz. Glomus, Acaulospora, Scutellospora, Gigaspora and Entrophospora, were recovered. Glomus was the dominant genus, three species of which were sporocarpic forms. Maximum site species richness (SR) ranged from 16 to 5. Species richness was maximum in A. ilicifolius where seven species of three genera were recovered. Based on relative abundance (RA) and isolation frequency (IF), two common species, viz. G. intraradices and A. laevis, were recovered from all seven sites.

Spatial Variations in Arbuscular Mycorrhizal (AM) Fungi Associated with Carica papaya L. in a Tropical Agro-Based Ecosystem

ABSTRACT Studies were carried out on the arbuscular mycorrhizal status of Carica papaya L. in a tropical agro-based ecosystem. Three geographic localities, Western Ghats, plateau and coastal area from two districts of Goa, India were selected for the study. In all, six sites were selected for the study. In the present investigation, the occurrence of arbuscular mycorrhizal association was recorded in papaya sampled at all the study sites and was characterized by the presence of hyphae, arbuscules and vesicles. At any given geographical locality, papayas sampled from North Goa recorded a comparatively higher total root colonization and spore density than papayas sampled from South Goa. In general, the papayas sampled from Western Ghats had highest root colonization and spore density of arbuscular mycorrhizal fungi (AMF) followed by plateaus and coastal areas, respectively. Pearsons correlation and backward regression analysis revealed that root colonization and spore density were influenced by pH, E.C., organic carbon, N, P, Zn and Mn. The present study recorded a total of 23 species of arbuscular mycorrhizal fungi belonging to four genera, Acaulospora, Gigaspora, Glomus and Scutellospora. Species richness of arbuscular mycorrhizal fungi for any given geographical locality was higher in semi organically to organically managed farms of South Goa than in conventionally managed farms of North Goa. The present study indicates spatial variations of arbuscular mycorrhizal fungi in Carica papaya L. in a tropical agro- based ecosystem and the fact that numerous factors affect these variations.

Seasonal Diversity of Arbuscular Mycorrhizal Fungi in Mangroves of Goa, India

Seasonal dynamics of arbuscular mycorrhizal (AM) fungal community composition in three common mangrove plant species, namely, Acanthus ilicifolius, Excoecaria agallocha, and Rhizophora mucronata, from two sites in Goa, India, were investigated. In all three species variation in AM fungal spore density was observed. Maximum spore density and AM species richness were recorded in the premonsoon season, while minimum spore density and richness were observed during monsoon season at both sites. A total of 11 AM fungal species representing five genera were recorded. Acaulospora laevis was recorded in all seasons at both sites. Multivariate analysis revealed that season and host coaffected AM spore density and species richness with the former having greater influence than the latter.

Symbiotic interactions between arbuscular mycorrhizal (AM) fungi and male papaya plants: its status, role and implications.

Experiments were conducted to study the arbuscular mycorrhizal (AM) status and its role in P-uptake through assay of root phosphatases activities in four varieties of male Carica papaya L. viz. CO-1, CO-2, Honey Dew and Washington during flowering stages. In the present study, mean total root colonization of AM fungi recorded peak increase in flowering stage-II while mean root phosphatase (acid and alkaline) activities recorded peak increase in flowering stage-I. Unlike root colonization and root phosphatase activities, spore density did not exhibit any definite patterns and recorded a narrow range of fluctuation during different flowering stages of male C. papaya. The study brought out the fact that root colonization and spore density of AM fungi along with root phosphatase activities varied significantly within the four varieties of male C. papaya plants during each flowering stage. The study also recorded consistently higher acid root phosphatase activity than alkaline root phosphatase activity under P-deficient, acidic soil conditions during all flowering stages of male C. papaya plants. Studies revealed that the root colonization of AM fungi influenced root phosphatase activities (acid and alkaline) positively and significantly during all flowering stages of male C. papaya plants. A total of twelve species of AM fungi belonging to five genera viz. Acaulospora, Dentiscutata, Gigaspora, Glomus, and Racocetra were recovered from the rhizosphere of male C. papaya plants.

Spatio-temporal variations of arbuscular mycorrhizal (AM) fungi associated with Carica papaya L. in agro-based ecosystem of Goa, India

Studies were carried out on spatio-temporal variations of arbuscular mycorrhizal (AM) fungi associated with Carica papaya L. growing in two different geographic localities in Goa, India – Western Ghats and coastal area, differing in soil characteristics and plantation status. The study recorded considerable variation in root colonization, spore density and distribution of AM fungi in the selected sites. The mean total root colonization was at a maximum in the month of July, while spore density was highest in April. The study recorded a total 33 species of AM fungi. Western Ghats recorded a relatively higher diversity of AM fungi compared to coastal area. Species richness of AM fungi was at a maximum in April and coincided with maximum mean spore density. Edaphic as well as climatic factors influenced the AM fungal parameters. The study recorded the existence of seasonality in AM fungi.

Use of Arbuscular Mycorrhiza and Organic Amendments to Enhance Growth of Macaranga peltata (Roxb.) Müll. Arg. in Iron Ore Mine Wastelands

Macaranga peltata (Roxb.) Mull. Arg. is a disturbance tolerant plant species with potential in mine wasteland reclamation. Our study aims at studying the phyto-extraction potential of M. peltata and determining plant-soil interaction factors effecting plant growth in iron ore mine spoils. Plants were grown in pure mine spoil and spoil amended with Farm Yard Manure (FYM) and Vermicompost (VC) along with arbuscular mycorrhizal (AM) species Rhizophagus irregularis. Pure and amended mine spoils were evaluated for nutrient status. Plant growth parameters and foliar nutrient contents were determined at the end of one year. FYM amendment in spoil significantly increased plant biomass compared to pure mine spoil and VC amended spoil. Foliar Fe accumulation was recorded highest (594.67μg/g) in pure spoil with no mortality but considerably affecting plant growth, thus proving to exhibit phyto-extraction potential. FYM and VC amendments reduced AM colonization (30.4% and 37% resp.) and plants showed a negative mycorrhizal dependency (–30.35 and –39.83 resp.). Soil pH and P levels and, foliar Fe accumulation are major factors determining plant growth in spoil. FYM amendment was found to be superior to VC as a spoil amendment for hastening plant growth and establishment in iron ore mine spoil

Enhancement of seed germination in Macaranga peltata for use in tropical forest restoration

We used pre-sowing treatments viz., soaking seeds in concentrated sulphuric acid (CSA), gibberellic acid (GA), combined treatment of CSA + GA and mechanical scarification to overcome seed dormancy and enhance synchronous germination of Macaranga peltata seeds. We analysed percent seed germination data by logistic regression and confirmed that except in GA treatment, time and acid concentration together were crucial for enhancing germination. The combination treatment of CSA and GA resulted in higher percent germination (up to 74%) than either treatment used separately, but produced defective seedlings (26%). Mechanical scarification of seed coat had the greatest impact in enhancing germination (78%) and reducing imbibition time (6 days) against the control (0%). Germination studies and SEM analysis confirmed that seed germination in M. peltata was inhibited by seed coat dormancy.

Screening for efficient AM (arbuscular mycorrhizal) fungal bioinoculants for two commercially important ornamental flowering plant species of Asteraceae

The objective of this study was to screen for the most efficient arbuscular mycorrhizal (AM) fungal bioinoculant and to evaluate possible effects of inoculation of different species of AM fungi on growth, yield, and flower fresh weight loss in two ornamental plant species of commercial importance, Chrysanthemum morifolium Ramat. and Tagetes erecta L. The research work was carried out in 2010–2011. The treatments included uninoculated control and plants inoculated with pure cultures of AM species (Acaulospora laevis, A. scrobiculata, Glomus coremioides, G. intraradices G. fasciculatum, G. mannihotis and Gigaspora albida). A complete randomized block design in factorial arrangement with five replicates was employed. Root and shoot length and dry weight, number of lateral branches, number of days required for flowering, and number, diameter, fresh weight of flower and fresh weight loss of flower/day were recorded. Results showed that inoculation of AM species had a significant effect on plant growth and flower quantity and quality. Increased flower number in C. morifolium (11–22%) and T. erecta (13–66%) was observed upon AM inoculation compared with the uninoculated control. Glomus intraradices proved to be the most efficient AM fungal bioinoculant, increasing flower number in both the plant species. This is attributed to its ability to colonize and multiply at a faster rate than the other AM fungal species used in the study.

Enhancement of Seed Germination in Trema orientalis (L.) Blume—Potential Plant Species in Revegetation of Mine Wastelands

Natural forest succession takes a long time to accumulate sufficient nutrients to support plant growth and enhance soil microbial activity. Human intervention in selecting native pioneer plant species is therefore required to accelerate sustainable restoration. Trema orientalis (L.) Blume, a fast growing pioneer plant species, has the ability to grow in nutrient deficient soils and proves to have reclamation potential in mine wastelands. However, its use has been limited due to low germination percentages and nonsynchronous seed germination. In the present study we tested the effect of sulphuric acid (H2SO4), hydrochloric acid (HCl), gibberellic acid (GA3), and potassium nitrate (KNO3) in varying concentrations and time durations on germination percentages and seed germination synchrony. We found that all treatments had a significant effect in predicting seed germination probabilities. Logistic regression analysis revealed that treatment solution and concentration had a significant effect on seed germination. Treatment with concentrated H2SO4 for 15 min increased germination up to 92% within 20 days with the least imbibition time (8 days) and highest Seedling Vigor Index (491). The scanning electron microscope images of seeds treated with H2SO4 showed complete dissolution of the honeycomb-like network of deposits on the seed coat surface removing the physical barrier and enhancing germination.