Rhizobia in tropical legumes—VII. Effectiveness of different isolates on Psophocarpus tetragonolobus (L.) DC

Rhizobia isolated from fourteen different genera of legumes were tested for their N-fixing effectiveness with Psophocarpus tetragonolobus in standard Leonard jar trials. Isolates from all plants except Pithecellobium jiringa were able to form nodules with P. tetragonolobus although a wide range of effectiveness amongst the different rhizobia was demonstrated. Thus P. tetragonolobus may be considered promiscuous with respect to its rhizobial requirements. Based on this experiment, a group of rhizobia comprising three elite strains (RRIM 56 from P. tetragonolobus, UMKL 36 from Lablab purpureus and CB 756 from Macrotyloma africanum, a moderately effective strain (NGR 258 from P. tetragonolobus), and two strains of low effectivity (RRIM 968 from Centrosema pubescens and UMKL 12 from Phaselus angularis) were selected for further study. When these were used to inoculate P. tetragonolubus growing in soil taken from virgin jungle (less than 1.54 rhizobia g^?1 soil); RRIM 56 and UMKL 36 again performed well, but NGR 258 outperformed CB 756.     

Rhizobia in tropical legumes—VIII. Serological characteristics of Psophocarpus tetragonolobus (L.) DC. isolates

Antisera were prepared against six inoculant strains of rhizobia for Psophocarpus tetragonolobus, and used to react with 62 different strains in both agglutination and immunodiffusion systems. A wide array of reactions occurred, indicating the extent of heterogeneity amongst strains capable of nodulating the same host. In agglutination reactions, the heat-stable somatic antigens could be arranged in 25 serogroups. In gel diffusion, antigens which produced strong precipitin bands usually showed agglutination relationships, but the corollary was not true. The immunodiffusion technique easily distinguished homologous and cross-reacting reactions and could be reliably used in field experiments with P. tetragonolobus.     

Rhizobia in tropical legumes—X. Growth in coir-dust-soil compost

Conditions affecting the growth of two rhizobia (RRIM 968 isolated from Centrosema pubescens and CB 1809 from Glycine max) in the coir-dust-soil compost used in Malaysia were examined. Whilst differences in growth between the two isolates were observed, recommended conditions for rhizobial production are: compost—(coir-dust 8 g; Sungei Buloh series soil—25 g ; calcium carbonate—5 g; and distilled water—60 ml) incubation—at 25°C for 12d; storage—commercially for about 3 months at 20°C. Under these conditions more than 10⁹ viable rhizobial cells·g^?1 compost are obtainable, while more than 10⁸·g^?1 survive 5 months in storage.Addition of a “sticker” (methyl-ethyl cellulose) to the compost during incubation was encouraging.     

Rhizobia in tropical legumes—XI. survival in the seed environment

Factors affecting rhizobia in the seed environment of the legumes Cajanus cajan, Centrosema pubescens, Glycine max, and Psophocarpus tetragonolobus were investigated. These included the effects of fungicides, insecticides, and herbicides on the survival and growth of rhizobia on agar and in liquid cultures. The pesticides used varied in their toxicity towards rhizobia but many fungicides and insecticides could be used in the vicinity of inoculated seeds. Certain fungicides and insecticides were shown to have little or no effect on the Rhizobium-legume symbiosis of C. cajan, C. pubescens, G. max, and P. tetragonolobus when added directly to inoculated seed. Various protective pelleting procedures were investigated including preparation of coating materials containing rock phosphates from different localities, talc, and bonemeal. These were applied to the seed in mixtures suspended in aqueous solutions of substituted celluloses, or gum arabic. Talc and Christmas Island rock phosphate both proved satisfactory, while “Cellofas” is recommended as the adhesive in this formulation. Soaking seeds before pelleting in an effort to remove anti-rhizobial substances from G. max seeds was beneficial in the case of soyabean cultivar KS437, but harmful when applied to Palmetto seeds.     

The colonization of host-root and soil by Rhizobia—I. Species and strain differences in the field

Growing-season populations of rhizobia associated with annual host-plant roots and nearby soil were examined in a field soil showing a nodulation problem in the second year after establishment. Rhizobium lupini reached higher populations at a faster rate than R. trifolii. A sharp drop in the population of R. trifolii associated with subterranean clover roots early in the growing season was followed by a recovery to high numbers. No such phenomenon occurred with R. lupini. The numbers of rhizobia under patches of non-nodulated plants in second-year stands were very low, usually <5/g soil, whereas the numbers under healthy plants in problem stands were similar to those under established stands. Differences in the colonization of both root and soil by R. trifolii in the first year were reflected in the second-year nodulation.     

The spread and development of Rhododendron ponticum L. on dunes at Winterton,Norfolk, in comparison with invasion by Hippophaë rhamnoides L. at Saltfleetby,Lincolnshire

A survey was made in 1972, of the status of Rhododendron pronticum L. at Winterton, Norfolk, and aerial photographs were used to assess its spread in recent years. The ecological implications of the continuing presence of this invsive alien shrub on the dunes are discussed. Comparisons with the highly successfull dune shrub Hippophaë rhamnoides L. help put into perspective the present and likely future role of Rhododendron at Winterton. The implications of controls are discussed together with methods by which this may be achieved.     

Are forests potential landscape barriers for foraging bumblebees? Landscape scale experiments with Bombus terrestris agg. and Bombus pascuorum (Hymenoptera, Apidae)

Habitat fragmentation is generally considered to have detrimental effects on insect movement and associated pollen flow between plant populations. Against this background the role of forests as potential barriers for foraging bumblebees of the species Bombus terrestris agg. and Bombus pascuorum was studied in different experiments. Bombus terrestris agg. workers were found foraging at distances of up to 2.2 km from their nests. B. terrestris agg. as well as B. pascuorum individuals crossed 600 m of forestland between floral mass resources (Phacelia tanacetifolia, Helianthus annuus), although in general a high degree of site fidelity was observed. B. pascuorum workers accepted artificial floral resources within the forest, whereas the minor use of resources below forest canopy observed for B. terrestris agg. possibly indicates a preference for direct forage flights, probably leading above the forest canopy. Our results warn against experiments with genetically modified crop species with potential bumblebee pollination (e.g. Brassica napus), in which an isolating effect of forests is assumed.     

Comparison of volatile constituents of Persicaria odorata(Lour.) Soják (Polygonum odoratum Lour.) and Persicaria hydropiper L. Spach (Polygonum hydropiper L.)

Polygonum odoratum Lour. has been reclassified as Persicaria odorata (Lour.) Soják [Wilson, K. L. Polygonum sensu lato (Polygonaceae) in Australia. Telopea 1988, 3, 177-182]; other synonyms currently used are Vietnamese mint or Vietnamese coriander and, in Malaysia, Daun Laksa or Laksa plant. The aerial parts of Laksa plant are highly aromatic, and they contain many organic compounds such as (Z)-3-hexenal, (Z)-3-hexenol, decanal, undecanal, and dodecanal that are typical for green, citrus, orange peel, and coriander odors. In addition to these aldehydes, 3-sulfanyl-hexanal and 3-sulfanyl-hexan-1-ol were discovered for the first time in this herb. The fresh leaves are pungent when they are chewed, although the active compound has never been identified. The pungency of Persicaria hydropiper (L.) Spach (formerly Polygonum hydropiper L., synonym water pepper) is produced by polygodial, a 1,4-dialdehyde derived from drimane terpenoids. We also identified polygodial as the active pungent compound in P. odorata (Lour.) Soják.     

Biodegradation of litter in Eucalyptus pauciflora communities—II. Fungal succession in fungicide- and insecticide-treated leaves

Fungal succession on untreated and fungicide- and insecticide-treated leaves of Eucalyptus pauciflora was compared. Natural succession on untreated leaves fits the general scheme for succession on deciduous tree leaves. Initial colonizers are species of Coelomycetes and Moniliales. When the numbers of Coelomycetes decrease in the late stages of decomposition, the frequency of Penicillium species and species of Zygomycetes increases. The succession is affected only marginally by DDT and dieldrin treatment while benomyl severely restricts the occurrence of most fungal species. The effect of benomyl persists even after exposure for 48 weeks in the field.     

Ecological studies of root-nodule bacteria introduced into field environments—6. Antigenic and symbiotic stability in Lotononis rhizobia over a 12-year period

Rhizobia suited to Lotononis bainesii do not occur naturally in Australia. Two serologically distinct strains of African origin were introduced into an isolated field station where perennial Lotononis-pangola grass pastures are grazed. Paddocks varied in the period of rhizobial occupancy from 5–12 years. Stability of four rhizobial characters: colony colour, effectiveness, cell antigens and antibiotic sensitivity were assessed from nodules on persisting Lotononis. Both strains became established throughout the 782 ha. No changes were observed in colony colour or serological reaction. Symbiotically, 8.5% of isolates had a lower N fixing capacity than stock cultures held in the laboratory although there were no ineffective isolates. Change in effectiveness was unrelated to serotype or to time of occupancy. There was also little change in antibiotic sensitivity although one isolate was tolerant to 15 parts/10⁶ streptomycin. The red bacterium Protaminobacter rubra was recorded for the first time as a cohabitant of Lotononis nodules. It is concluded that colony colour, serological and symbiotic properties are sufficiently stable to be of use in long-term ecological studies although antibiotic sensitivity appears less stable.     

Enzymatic Activities in Soil Cultivated with Coffee (Coffea arabica L. cv. ‘Bourbon’) and Amended with Organic Material

The objective of this study was to investigate the growth of coffee (Coffea arabica L. cv. ‘Bourbon’) in soil amended with compost, vermicompost, and bokashi at 25%, 50%, and 66% while mycorrhizal colonization and activity of acid and alkaline phosphatases and urease in soil were monitored. Treatments with 25% compost as well as higher application rates of compost and bokashi (50% or 66%) increased coffee growth. Shoot fresh weight increased 5 times when 25% bokashi or compost was applied, 8 times when 50% was applied and 10 times when 66% was applied compared to the control plants without organic fertilizer. Acid and alkaline phosphatase and urease activity increased when organic fertilizer was applied to soil. Application of organic fertilizers increased the growth and fresh weight of root and shoot of coffee plants and improved the root mycorrizal colonization and enzymatic activity of the soil.     

Optimum Phosphorus Concentration for Growth of Catharanthus roseus (L.) G. Don ‘Pacifica White’ in a Subirrigation and Top Watering System

The objective of this study was to quantify the optimum rates of water-soluble phosphorus (P) on the growth of Catharanthus roseus (L.) G. Don ‘Pacifica White’ in soilless media in a recirculating subirrigation and top watering system. The experiment was designed so that only P varied between treatments; nitrogen (N), ammoniacal N to nitrate N ratio, and potassium (K) content were held constant. Media pH decreased with increasing P concentration in the nutrient solution in both the subirrigated and top-watered plants. Shoot N, P, K, magnesium, manganese, zinc, and copper were in general greater in the subirrigated plants when compared to top-watered plants. Shoot calcium, sulfur, iron, aluminum, and boron were greater in top-watered plants when compared to subirrigated plants. Optimal plant growth was achieved at ≥0.5 mM P in the subirrigated and top-watered plants, which is lower than what is usually commercially applied. Subirrigated plants were of greater quality and dry mass regardless of P concentration in the nutrient solution, when compared to top-watered plants.     

Does moder development along a pure beech (Fagus sylvatica L.) chronosequence result from changes in litter production or in decomposition rates?

The development of temperate deciduous and conifers forests stands usually results in accumulation of forest floor organic matter and a shift from mull to moder humus forms. It has been suggested that an increase in nutrient uptake by trees during their rapid growth phase leads to topsoil acidification, decrease in earthworm density and thereby a decrease in litter turnover. The focus of this paper was to examine if the mull-moder shift with forest ageing results from higher leaf litter production and/or lower litter decay rates. The objectives of this research were to determine (1) changes in macro-morphological properties of humus forms, leaf litter production, litter decay rates, soil nutrients content and pH along a 130-year pure beech (Fagus sylvatica L.) chronosequence in Normandy (Northwest France), (2) if humus form varied from mull to moder with increasing stand age, and (3) if a shift from mull to moder resulted from increased litter production, decreased litter decay rates, or both. Annual litter production did not change significantly along the chronosequence (mean 2.41 t ha⁻¹). In contrast, litter decay rates decreased significantly during the rapid growth phase of trees. In consequence, the litter turnover time (1/k) was lower in the youngest stands (20 months) compared to the oldest ones (31 months). Even in the absence of a significant pattern of variation, litter production was positively correlated with the thickness of the OF (Oi) horizon. In contrast, litter decay was strongly negatively correlated with maximum thickness of the OH (Oa) horizon, suggesting that the appearance of the humification layer was mainly due to a decrease in litter decay rate. We did not find significant changes in the main properties of the organo-mineral horizon, suggesting that soil nutrient availability may not directly affect litter dynamics. We concluded that moder development along the chronosequence resulted in decreasing litter decay rates during the aggradation phase while litter production was stable. Further studies are required to identify the ecological factors responsible for moder development along forest ageing.     

AM fungi lead to fertilizer phosphorus economy and enhanced system productivity and profitability in okra (Abelmoschus esculentus L.)–pea (Pisum sativum L.) cropping system in Himalayan acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, Himachal Pradesh, India, during 2009–2011 to economize inorganic phosphorus (P) and enhance profitability of okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF). A field experiment was replicated thrice in a randomized block design comprising 14 treatments involving AMF (Glomus mosseae) at varying inorganic P (50%, 75%, and 100% of recommended soil test-based P dose) and irrigation regimes (40% and 80% available water capacity] in a Himalayan acid Alfisol. In okra, AMF inoculation at varying P and irrigation regimes registered higher P response ratio (PRR), net returns (10–18%), and benefit:cost (B:C) ratio (17–49%) compared to “generalized recommended P dose (GRD)” and their non-AMF counterparts. Similarly in pea, AMF inoculation at varying P and irrigation regimes again registered higher PRR, net returns (14–23%), and B:C ratio (10–58%) compared to GRD and non-AMF counterparts. Higher system productivity (7–16%) and profitability in terms of net returns (9–23%) and B:C ratio (10–54%) were also registered in AMF-imbedded treatments compared to non-AMF counterparts. Further, “AMF + 75% soil test-based P dose” at either of these irrigation regimes registered statistically similar okra–pea system productivity and profitability as that obtained under “100% soil test-based P dose” at either of two irrigation regimes, thus indicating an economy of soil test-based applied P dose by about 25%. Overall, the current study suggests that practice of AMF inoculation has great potential in enhancing system productivity and profitability besides cutting down about 25% inorganic P requirement in okra–pea production system in the Himalayan acid Alfisol.     

The colonization of host-root and soil by rhizobia—II. strain differences in the species Rhizobium trifolii

The ability of four strains of Rhizobium trifolii to colonize host-root and soil was compared at 5-day intervals up to 70 days from sowing into a field soil. Strain differences in colonizing ability were demonstrated, with one strain (TA1) consistently inferior to the other three which comprised another introduced strain (UNZ29) and two locally isolated strains.     

Accumulation mechanism of γ-aminobutyric acid in tomatoes (Solanum lycopersicum L.) under low O2 with and without CO2

The storage of ripe tomatoes in low-O(2) conditions with and without CO(2) promotes γ-aminobutyric acid (GABA) accumulation. The activities of glutamate decarboxylase (GAD) and α-ketoglutarate-dependent GABA transaminase (GABA-TK) were higher and lower, respectively, following storage under hypoxic (2.4 or 3.5% O(2)) or adjusted aerobic (11% O(2)) conditions compared to the activities in air for 7 days at 25 °C. GAD activity was consistent with the expression level of mRNA for GAD. The GABA concentration in tomatoes stored under hypoxic conditions and adjusted aerobic conditions was 60-90% higher than that when they are stored in air on the same day. These results demonstrate that upregulation of GAD activity and downregulation of GABA-TK activity cause GABA accumulation in tomatoes stored under low-O(2) conditions. Meanwhile, the effect of CO(2) on GABA accumulation is probably minimal.     

Intra‐specific variation for salt tolerance in a potential oil‐seed crop,brown mustard (Brassica juncea (l.) Czern. and Coss.)

Thirty eight accessions of brown mustard (Brassica juncea (L.) Czern. and Coss.) were screened after two weeks growth in solution culture containing 120 mol m‐³ NaCl. Considerable variation for salt tolerance was observed in this set of germplasm, since some accessions showed relatively vigorous growth in saline medium.

In order to determine the consistency of degree of salt tolerance at different growth stages of crop life cycle two salt tolerant accessions, P‐15 and KS‐51 and two salt sensitive 85362 and 85605 were tested at the adult stage in 0(control), 100 and 200 mol m^‐3 NaCl. Both the tolerant accessions produced significantly greater fresh and dry biomass and had considerably higher seed yield than those of the salt sensitive accessions. Analysis of different ions in the leaves showed that salt tolerant accessions contained greater amounts of Na⁺, K⁺ and Ca²⁺ than the salt sensitive accessions, although they did not differ significantly for leaf Cl^‐. Only one salt tolerant accession P‐15 had greater leaf K/Na ratio and K⁺ versus Na⁺ selectivity compared with the tolerant KS‐51 and the two salt sensitive accessions.

From this study it was established that there is a considerable variation for salt tolerance in B.juncea which can be exploited by selection and breeding for improvement of its salt tolerance. Since the degree of salt tolerance in B.juncea does not change at different growth stages of the crop life cycle, selection for salt tolerance at the initial growth stages could provide individuals that would be tolerant at all other growth stages. Accumulation of Na⁺, K⁺ and Ca²⁺ in the leaves are important components of salt tolerance in B.juncea.     

Psidium guajava (L.)—a Bioeconomic Plant for Restoration of Industrial Solid Waste Dump: a Green and Sustainable Approach

Water, Air, & Soil Pollution - Air pollution, especially heavy metals in PM2.5, has gradually become one of the most serious environmental problems in cities, which might cause various...     

Effects of benomyl on vesicular‐arbuscular mycorrhizal infection of red clover (Trifolium pratense L.) and consequences for phosphorus inflow.

The roots of red clover plants inoculated with the vesicular‐arbuscular mycorrhizal fungus Glomus clarus Nicolson & Schenck were treated with a drench of benomyl at a time when mycorrhizal infection was already well established. Benomyl halted further infection and reduced phosphorus inflow by one order of magnitude compared to untreated controls. The fungicide also decreased the rate of plant growth probably as a consequence of reduced phosphorus inflow.     

Farmers’ adoption of maize (Zea mays L.) hybrids and the persistence of landraces in Southwest China: implications for policy and breeding

This paper examines changes in the distribution of maize hybrids and landraces in the mountainous areas of southwest China over 1998–2008, farmers’ reasons for cultivar adoption and the implications for national policies in relation to seed production and breeding, based on baseline data and a survey conducted in Guangxi, Yunnan and Guizhou. The study traced the dynamic changes in the adoption of hybrids and landraces in farmers’ fields, explored how individual farmer’s choices can influence local landrace distribution, and investigated the space for conducive policy and innovative action for on-farm conservation of maize genetic resources. The research showed that although there is strong farmers’ interest in accessing modern maize hybrids, farmers also express strong reasons for maintaining at least some of the landraces that satisfy local agronomic context and social preferences. Farmers recognized that hybrids have a number of advantages but they also indicated some disadvantages of the current available hybrids e.g. with respect to seed quality, local adaptability, taste and cost of seeds, but also lack of information on the performances of the new hybrids. Based on farmers’ reasoning and experiences, the requirements have been identified for improving yield combined with local preferences (agronomic, cultural and socio-economic). The paper concludes by identifying options for how China might seek to develop resilient seed systems for smallholder farmers in poor areas, under changing climatical conditions and volatile markets. Participatory Plant Breeding is among the options considered for bringing farmers’ needs into conservation and breeding strategies for improving local adaptation.