Field assessment of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> based mycoherbicide for control of <Emphasis Type="Italic">Striga hermonthica</Emphasis> in Nigeria

Fusarium oxysporum (isolate PSM 197) based mycoherbicide was evaluated for its efficacy under field conditions in trials conducted during 1999--2001 cropping seasons in the Nigerian savanna. In the 1999 cropping season, spot application of 5--10 g of mycoherbicide was found to give effective control of Striga hermonthica. Results of on-farm trials at Barhim and Dutsen-Ma areas showed the application of the mycoherbicide to significantly (p= 0.05) increase stand count at both 3 weeks and at harvest, reduced Striga shoot count and increased crop yield in both improved and local sorghum varieties, as compared with the same varieties not treated with the mycoherbicide. Results establish the efficacy of F. oxysporum as a mycoherbicide and the need for further development of the mycoherbicide into formulated granules or seed treatment for use in control of S. hermonthica under field conditions.     

Chlamydospore Production,Inoculation Methods and Pathogenicity of Fusarium oxysporum M12-4A,a Biocontrol for Striga hermonthica

Fusarium oxysporum isolate M12-4A is currently being evaluated for the biological control of Striga hermonthica . Inoculum production, inoculum delivery to the target, chlamydospore germination, and weed growth suppression of this weed-pathogen system were investigated. Liquid fermentation systems using organic material were evaluated for the production of large numbers of chlamydospores. A 1% sorghum straw powder (< 1 mm) substrate, exposed to black light at 21°C for 21 days, yielded 3.23 X 10 8 colony forming units (CFU) l -1 medium. A two-stage fermentation system using 5% w/v straw substrate under black light at 30°C for 14 days yielded 3.5 X 10 8 CFU l -1 medium. In vitro variations in chlamydospore germination were governed by the presence of exogenous carbon, nitrogen, and sorghum root exudates. Ammonium-nitrogen compounds and urea, in combination with glucose had a stronger stimulatory effect on chlamydospore germ tube growth than did potassium nitrate. Maximal germ tube elongation occurred when chlamydospores were exposed to urea at a C/N ratio of 10. Some mineral solutions and sorghum root exudates inhibited chlamydospore germ tube elongation; however, arabic gum, a complex polysaccharide, stimulated chlamydospore germ tube elongation and the production of secondary chlamydospores. In field trials, chlamydospore powder harvested from small-scale fermenters reduced S. hermonthica emergence by 92%. Complete inhibition of S. hermonthica emergence occurred when the chlamydospore powder was added to the soil at sowing and when sorghum seeds coated with chlamydospores were sown. Effective biological control of S. hermonthica was achieved using a simple fermentation system with sorghum straw as the inoculum growth substrate. For inoculum delivery to the farmers' fields, sorghum seeds were coated with the inoculum using arabic gum as the adhesive. This simple delivery system permits a uniform inoculation of the field as well as the proper positioning of the inoculum in the immediate environment of sorghum roots, where S. hermonthica attaches to its host. To facilitate a broad usage of F. oxysporum M12-4A for the biocontrol of S. hermonthica , we propose an inoculum production strategy based on a cottage industry model that utilizes a liquid fermentation process and inexpensive locally-available substrates including sorghum straw and arabic gum.     

Efficacy of crude neem seed kernel oil (NSKO) in controlling the tree locust (Anacridium melanorhodon melanorhodon Walker), a serious pest of the gum arabic producing tree (Acacia senegal L. Willd.) in the Sudan

The present study was carried out at Al Semih (western Sudan) (13° 14′ N: 30° 27′ E: Alt. 550 m). The area is part of the gum arabic belt which is heavily populated with farmers who practice shifting cultivation and/or agroforestry where Acacia senegal L. Willd (the main gum arabic producing tree) is dominant. The tree locust (Anacridium melanorhodon melanorhodon Walker (Orthoptera, Acrididae) is a serious pest of A. senegal. Farmers practice agroforestry within the gum belt where they cultivate their crops e.g. millet, groundnut, sesame and sorghum between A. senegal trees. Gum Arabic is an important source of revenue for farmers. Chemical pesticides have been used to control the tree locust. Although the gum belt (where A. senegal grows) is heavily populated, pesticides are used to control the tree locust in the area. The present study was undertaken with the objective of using alternative environmentally safe pesticides. Several doses of neem seed kernel crude oil (NSKO) were tested against the 4^th, 5^th, 6^th instars and the mature tree locust (A. melanorhodon melanorhodon) in a completely randomized block design. Experiments were carried out in cages placed on part of the gum arabic belt. NSKO at high doses (5 and 10% v/v) significantly reduced feeding, moulting and ovipositing of the tree locust and significantly increased the mortality of all developmental stages tested. However, low doses of NSKO had no significant effect on the tree locust.     

Fusarium oxysporum f. sp. strigae strain Foxy 2 did not achieve biological control of Striga hermonthica parasitizing maize in Western Kenya

The production of maize, a major staple food crop in sub-Saharan Africa is being constrained by the parasitic weed Striga hermonthica. The fungus Fusarium oxysporum f. sp. strigae (Foxy 2) that causes fusarium wilt of Striga in Ghana, West Africa, is being considered for biological control of the weed in Western Kenya. The present study investigated the efficacy of F. oxysporum f. sp. strigae (Foxy 2) for S. hermonthica management in Western Kenya. Research was conducted in post-entry quarantine (PEQ) facilities at Alupe, Busia, Homabay, Kibos and Siaya field stations for two seasons. Each PEQ was a split-plot, with 4 main blocks each having 6 treatment subplots. The treatments included seeds of two S. hermonthica-susceptible maize varieties, either coated with Foxy 2 using gum Arabic, gum Arabic alone, or left untreated. Data was collected over seven sampling periods on S. hermonthica population per plant, percentage of those that were wilting, and the severity of wilting. Maize plant growth parameters assessed included duration to 50% anthesis and 50% silking, plant height, number of leaves, stover and cob weights, and maize yield per hectare. Statistical analysis was done using SAS 9.1 software. Data on S. hermonthica population were analyzed by χ²-test using Proc Genmod (Poisson); while the other parameters were analyzed by Proc Mixed using study location, season and blocks as random effects, and the sampling periods as repeated effects. All the assessed parameters were similar between plants grown from seeds inoculated with F. oxysporum f. sp. strigae (Foxy 2), those coated with gum Arabic, and the ones without any coating. These parameters were also not different between the maize varieties. There are varying reasons for the disparities between results on F. oxysporum f. sp. strigae (Foxy 2) obtained in this Kenyan study, and those from researches outside this country. In conclusion, F. oxysporum f. sp. strigae strain Foxy 2 is predominantly safe on maize growth, but its efficacy in controlling S. hermonthica was not evident on the tested Kenyan soils.     

Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant Striga hermonthica in maize

Two trials were conducted to evaluate the efficacy of a granular mycoherbicide formulation based on Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant, Striga hermonthica in the Nigerian Savanna. Four fungal treatments were used: F. oxysporum followed by 2,4-D, F. oxysporum followed by supplementary hoe weeding, F. oxysporum followed by Triclopyr and a control (No F. oxysporum but hoe-weeded). The experiments were laid out in a split plot design with three replications in the two locations. The two varieties (Across 97 TZL and farmer's local variety) formed the main plot treatments, while the Striga fungal treatments formed the sub-plot treatments. At the Lafia location, the emergence of Striga was delayed by 7 days (46 days) as compared to the Makurdi location, which germinated earlier 39 days after sowing. Maize variety Across 97 TZL similarly delayed the time to Striga emergence when compared to the farmer's local variety. However, the different Striga control methods did not have any significant effect on the time of Striga emergence. Generally, number of maize plants infected with Striga was highest with the farmer's local variety throughout the period of observation, while in the Striga control treatments, hoe-weeded check recorded the highest; the minimum was obtained with plots treated with F. oxysporum followed by postemergence application of Triclopyr at the rate of 0.36 kg a.i./ha at 6 weeks after sowing. Highest maize grain yields were obtained at Lafia with Across 97 TZL and plots treated with F. oxysporum followed by either post-emergence 2,4-D or Triclopyr at 0.36 kg a.i./ha each. The results demonstrate the high potentiality of using F. oxysporum as a spot application at planting followed by post-emergence herbicide (2,4-D or Triclopyr) application at 6 weeks after sowing for the control of the parasitic plant S. hermonthica in the Nigerian Savanna.     

Root nitrogen concentration of sorghum above 2% produces least Striga hermonthica seed stimulation

A series of pot and laboratory experiments was carried out to assess the effects of N status of sorghum roots and timing of N application (as NH₄NO₃) on the germination of Striga hermonthica seeds. Root N concentrations varied from 10 to 26 mg N g^?1. The cut root and the root exudates technique used in assaying S. hermonthica seed germination gave similar results. However, the cut root technique was easier to handle and more discriminating at low germination levels. S. hermonthica seed germination per unit sorghum root mass followed a broken‐stick model. It decreased with increasing root N concentrations, reaching lowest levels at a root N concentration of 19.5 mg N g^?1, after which no further reduction occurred. It was not possible to reduce S. hermonthica seed germination to a zero level. Timing of N application influenced the time a higher N concentration is reached, not the S. hermonthica seed germination. Both timing and rate of N application are important in maintaining root N concentrations above 19.5 mg N g^?1, thereby potentially reducing S. hermonthica germination in the field. Translation of results to reductions in infection levels and yield losses is hampered by density‐dependent relations after the S. hermonthica germination stage.     

Does vacuum-packaging or co-delivered amendments enhance shelf-life of Striga-mycoherbicidal products containing Fusarium oxysporum f. sp. strigae during storage?

The effect of vacuum packaging on the shelf-life and handling of Pesta granules and seed treatment made with chlamydospores of Fusarium oxysporum strains Foxy2, PSM197 or their mixture was studied at 4°C and 22±3°C over 1 year. In addition, the effects of co-incorporated amendments [urea in Pesta or co-delivered fungicides (Ridomil Gold®, Apron XL®) on coated sorghum seeds], and coating material (Arabic gum ‘AG’, SUET Binder ‘SB’) on the viability of Striga-mycoherbicides were evaluated. Storage under vacuum packaging did not enhance shelf-life of the formulated Striga-mycoherbicidal products after 12 months of storage regardless of the treatment used. The co-incorporated urea into Pesta granules significantly reduced the viability of mycoherbicides, but less so at 4°C (58% strain-stability after 12 months). No significant differences between the coating materials in maintaining the viability of mycoherbicides were observed. The shelf-life of isolates on coated seeds significantly decreased when adding Ridomil Gold®. However, at 4°C, the fungicide Apron XL® allowed better survival of Foxy2 and PSM197 by maintaining their averaged half-lives (t _0.5) by an additional 6 months compared to Ridomil Gold®. In general, Striga-mycoherbicidal product combinations exhibited a significantly higher shelf-life when stored at 4°C than at 22±3°C. The absence of a positive effect of vacuum packaging on shelf-life of Striga-mycoherbicidal products reflects the tolerance of the formulated fungal propagules (chlamydospores) to withstand an oxygen enriched environment and allows their handling and distribution through ordinary packaging systems in Africa. The high compatibility between Striga-mycoherbicides and the co-delivered fungicide Apron XL®, and the fungal storage stability allows simultaneous control of Striga and fungal cereal diseases within an integrated pest management (IPM).     

Effects of carbon sources on extracellular lipase production and lipA transcription in Acinetobacter calcoaceticus

  The effects of lactic acid, oleic acid, gum arabic and their mutual interactions, on the production of extracellular lipase and the regulation of the expression of the lipase encoding gene (lipA) in Acinetobacter calcoaceticus were investigated. Formation of extracellular lipase was measured in culture supernatants of wild-type strain BD413 and expression of the lipA gene was monitored in vivo with a chromosomal fusion of lipA to lacZ. At the level of lipA expression only oleic acid had a significant effect; it lowered expression. Neither gum arabic nor lactic acid had any effect on lipA expression. On the other hand, the yield of extracellular lipase increased 2–5 times by the addition of gum arabic, possibly due to the release of cell surface-bound lipase. An interaction between oleic acid and lactic acid was also detected. Journal of Industrial Microbiology & Biotechnology (2000) 24, 25–30. Received 03 May 1999/ Accepted in revised form 04 September 1999     

Seed treatment technology: An attractive delivery system for controlling root parasitic weed Striga with mycoherbicide

Coating sorghum seeds with Fusarium oxysporum (Foxy 2) for control of the root parasitic weed Striga, appears to be an attractive option for minimizing the inoculum amount, establishing the biocontrol agent in the potential infection zone of the host plants, and offering a simple, easy and economical delivery system. Our investigations resulted in the selection of appropriate seed coating materials and a suitable type and form of fungal inoculum. The coating materials tested were arabic gum (AG10%, 20%, 40%), carboxymethylcellulose (CMC1%, 2%) and pectin (LS 440, LM-5 CS) 1%, while the fungal inoculum included microconidia and fresh and dried chlamydospores produced using different substrates. Foxy 2 survived the seed treatment processing and showed excellent viability on seeds for at least 8 months of storage after coating. In general, the performance of 40% arabic gum in combination with dried chlamydospores was the best among the other types of inoculum and coating material tested. Regardless of the type and form of inoculum and coating materials tested, Foxy 2 was able to colonize all roots, even root tips and hairs of the host (sorghum), thereby meeting important criteria of a promising candidate for controlling Striga when applied as a seed treatment. The efficacy of treated sorghum seed with Foxy 2 using different coating materials in reducing S. hermonthica infestation was evaluated in pot and root chamber trials. Foxy 2 markedly reduced Striga emergence and dry weight and increased the percentage of the diseased emerged Striga shoots. However, the efficacy of seed coating varied according to the type and form of fungal inoculum as well as coating material. Coating sorghum seed with dried chlamydospore inoculum homogenized into 20% arabic gum (as adhesive) showed the highest efficacy of 81 and 77% (i.e., percent reduction in healthy emerged Striga shoots compared to the control treatment) against Striga using either sterilized or non-sterilized soil, respectively. In root chamber bioassays, the application of Foxy 2 in combination with AG40% significantly caused disease in 77% of the germinated Striga seeds and in all tubercles after 25 days of sowing. These findings provide an optimized coating protocol as an attractive delivery system for bioherbicides for root parasitic weeds.     

Gas exchange of root hemi-parasite Striga hermonthica and its host Sorghum bicolor under short-term soil water stress

The gas exchange of the upper fully expanded leaf of the root parasite Striga hermonthica and of its host Sorghum bicolor was measured under wet and dry conditions to identify the mechanisms of the devastating effects of the parasite on its hosts under drought. The short-term water stress severely reduced photosynthetic rate in infected sorghum, but less in S. hermonthica. Soil water stress did not affect leaf respiration rate in either S. hermonthica or infected sorghum. This suggests that under dry conditions both infected sorghum and S. hermonthica decreased autotrophic carbon gain. The transpiration rate of S. hermonthica, a major driving force for assimilate uptake from the host, was higher and less affected by water stress than that of infected sorghum. Stomatal density on the abaxial surfaces of the leaves was higher in S. hermonthica than in sorghum. Both S. hermonthica infection and water stress decreased stomatal conductance of the sorghum leaves. S. hermonthica, irrespective of soil water status, had greater stomatal aperture on the adaxial and abaxial surfaces of its leaves than infected sorghum. These results indicate that the higher transpiration rate of S. hermonthica even under water stress, achieved through higher stomatal density on the abaxial surfaces of the leaves and greater stomatal aperture on both surfaces of the leaves, may induce the maintenance of water and solute transfers from the host to the parasite leading to severe damage to the host under drought.     

Identification of Intestinal Bacteria Responsible for Fermentation of Gum Arabic in Pig Model

Acacia spp. produce gum exudates, traditionally called gum arabic or gum acacia, which are widely used in the food industry such as emulsifiers, adhesives, and stabilizers. The traditional gum arabic is highly variable with average molecular weights varying from 300,000–800,000. For this reason a standardized sample was used for the present experiments, based on a specific species of gum arabic (Acacia(sen)SUPER GUM^TM EM2). The literature indicates that gum arabic can be fermented by the intestinal bacteria to short chain fatty acid, particularly propionate. However, the bacteria responsible for the fermentation have not been determined. In this study, we used enrichment culture of pig cecal bacteria from the selected high molecular weight specific gum arabic of (M_W 1.77 × 10⁶). We found Prevotella ruminicola-like bacterium as a predominant bacterium that is most likely to be responsible for fermentation of the gum arabic used to propionate.     

Biocontrol of broomrape using Fusarium oxysporum f. sp. orthoceras in tomato crops under field conditions

The effects of Fusarium oxysporum f. sp. orthoceras as a mycoherbicide on broomrape, a weedy parasite of tomato crops, were examined during two growing seasons under field conditions. In contrast to emerged broomrapes in treated plots, none of the tomato plants inoculated with fungal pathogen showed Fusarium-wilt symptoms. In 2008, both suspension concentrations, 1?×?10⁶ and 1?×?10⁷ spore/ml, used via either root-dip or soil-inoculation three weeks after transplanting, and high-concentration-soil-inoculation one week after transplanting, reduced the number of broomrape plant and shoots per plant compared to the control. In 2009, single-point-low-dose and twice-high-dose applications of sulfosulfuron had significantly fewer broomrape plants than high-concentration-soil-inoculation three weeks after transplanting. High-concentration-root-dip inoculation decreased broomrape biomass weight significantly by 58% compared to the control in 2008. In 2009, mean biomass for single-point-application of sulfosulfuron at 50 and 75?g levels was lower than control. The highest yield was detected in high-concentration-soil-inoculation at transplanting in 2008 and in low-dose-twice-application of sulfosulfuron in 2009. Tomato yield was associated with the number of broomrape shoots per plant. There is promise that these field-scale findings will improve attempts to use mycoherbicides for biocontrol of broomrapes in tomato cropping systems.     

Effect of the saprophytic fungus Fusarium oxysporum on arbuscular mycorrhizal colonization and growth of plants in greenhouse and field trials

Effects of the saprophytic fungus Fusarium oxysporum on arbuscular mycorrhizal (AM) colonization and plant dry matter were studied in greenhouse and field experiments. Host plants: maize (Zea mays L.), sorghum (Sorghum vulgare L.), lettuce (Lactuca sativa L.), tomato (Lycopersicum esculentum L.), wheat (Triticum vulgare L), lentil (Ervum lens L.) and pea (Pisum sativum L.), the AM fungi: Glomus mosseae, G. fasciculatum, G. intraradices, G. clarum, and G. deserticola and the carriers for F. oxysporum inoculum: aqueous solution, thin agar slices, and pellets of agar and alginate were tested under greenhouse conditions. Greatest plant growth and AM colonization responses in sterilized and unsterilized soils were observed with pea, Glomus deserticola and sodium alginate pellets as the carrier for F. oxysporum inoculum. Under field conditions, adding F. oxysporum increased the survival of transplanted pea, possibly through a beneficial effect on AM fungi. Application of F. oxysporum increased shoot dry matter, N and P concentrations of pea and sorghum plants, and the level of AM colonization attained by indigenous or introduced AM fungi. These parameters were similar in plants inoculated with either G. deserticola or with the indigenous AM fungi. Application of the saprophytic fungus increased the number of propagules of AM fungi in field plots in which pea was grown, but this increase was not sufficient to increase AM colonization of sorghum after the pea crop. This revised version was published online in June 2006 with corrections to the Cover Date.     

Immobilization of inulinase obtained by solid-state fermentation using spray-drying technology

Abstract

This work focuses on the immobilization of a crude inulinase extract obtained by solid-state fermentation using spray-drying technology. Maltodextrin and arabic gum were used as immobilizing agents. The effects of inlet air temperature, maltodextrin/arabic gum ratio and mass fraction of crude enzyme extract on the activity of immobilized inulinase were assessed using a central composite rotatable design (CCRD) (2³). The optimum operational conditions for the immobilization of inulinase by spray-drying was obtained at an inlet air temperature of 200°C, mass fraction of crude enzyme extract of 0.5 wt% and using only arabic gum as immobilizing agent. The immobilized enzyme had good thermostability, comparable with other inulinases obtained from different microorganisms. The method used gave good enzyme activity after immobilization and could be applied to other enzymes which have good thermal stability.     

Study of a single and mixed culture for the direct bio-conversion of sorghum carbohydrates to ethanol

Fusaium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae 2541 fermented soluble and insoluble carbohydrates of sweet sorghum stalk directly to ethanol. Both microorganisms were first grown aerobically and fermented sorghum stalk to ethanol thereafter. During fermentation, insoluble carbohydrates were hydrolysed to soluble sugars by the celluloytic system of F. oxysporum. Ethanol yields as high as 24.4 and 33.5 g/100 g dry stalks were obtained by F. oxysporum and the mixed culture respectively, representing a theoretical yield enhancement of 11.6% and 53.6% respectively. The corresponding ethanol concentrations in the fermentation medium were 4.6% and 6.4% (w/v). These results clearly demonstrated that a large portion of insoluble carbohydrate from sorghum was converted by simultaneous saccharification and fermentation to ethanol, making the process promising for bioethanol production.     

Tissue specific reactions of sorghum roots to the mycoherbicide Fusarium oxysporum f. sp. strigae versus the pathogenic F. proliferatum

Fusarium oxysporum f. sp. strigae (Foxy 2) is a mycoherbicide against Striga hermonthica. To ensure the safe use of this biocontrol agent, and as part of the risk assessment, this study was aimed at providing cytological evidence that Foxy 2 does not possess pathogenic behavior towards the non-target host sorghum. Therefore, we compared the infection processes and sorghum root tissue reactions towards the pathogenic F. proliferatum to that of Foxy 2 using light- and transmission electron microscopy. Given that during the growth process, hyphae could get into the central cylinder, tissue specific reactions of sorghum to Foxy 2 were also investigated by wounding the roots (exposing the vascular system), and testing for proliferation of hyphae within the vessels. Results showed that 2 weeks after sowing, F. proliferatum had invaded and destroyed all cell types including the central cylinder while Foxy 2 hyphae were located around the outer endodermal layer and were not able to penetrate the latter. There was an increase in blue autoflourescence in the central cylinder and especially the endodermis, probably due to increased phenolics in Foxy 2 infected roots which was not the case for F. proliferatum. This might contribute to the inability of Foxy 2 to penetrate the endodermis. Transmission electron microscopy showed extensive degradation of endodermis and vessel walls into thin translucent layers by F. proliferatum but not by Foxy 2. In the mechanically wounded and infected roots, Foxy 2 could invade the central cylinder close to the wound but was not identified a few millimeters away from the wound. This implies that it was not able to grow within or destroy the central cylinder even when already present within it; probably due to the observed increased phenolics. Thus, exposure of the vascular system did not serve as a route for the invasion of Foxy 2 which therefore could not further cause tracheomycosis. Therefore, Foxy 2 could be seen as a fungus well suited for biocontrol.     

贝莱斯芽孢杆菌GDND-2对烟草镰孢根腐病菌生长发育的影响

【背景】尖孢镰孢(Fusariumoxysporum)引起的烟草根腐病在世界烟区普遍发生,严重影响烟草产量和质量,化学农药无法有效防治病害,利用生防菌防治该病成为研究热点。【目的】明确贝莱斯芽孢杆菌(Bacillusvelenzensis)GDND-2对尖孢镰孢生长发育的抑制作用。【方法】制备含10%和20%GDND-2发酵滤液的PDA培养基,涂在玻片上,接种尖孢镰孢分生孢子,观察滤液对尖孢镰孢孢子萌发、菌丝生长、孢子形成和色素产生的影响,应用扫描和透射电镜观察菌体超微结构的变化。【结果】贝莱斯芽孢杆菌GDND-2发酵滤液延迟孢子萌发2h以上,造成芽管膨大畸形,促使菌丝提早分枝,抑制菌丝延伸,使菌丝产生畸形球状结构,10%和20%发酵滤液对菌丝生长抑制率达53.41%和61.58%。滤液延迟病菌产孢,显著抑制产孢量,影响孢子形态,刺激病菌产生色素。10%和20%发酵滤液延迟产孢20h和28h,对产孢量的抑制率为52.11%和78.85%,滤液促使病菌形成小型分生孢子。观察尖孢镰孢的超微结构,部分菌丝膨大、畸形,细胞壁变薄,细胞膜消失,细胞质渗出,胞内呈空腔结构;部分菌丝严重皱缩、扭曲、...     

Modification of alternan by novel Penicillium spp

Four strains identified as Penicillium spp. were isolated from soil samples based on their capacity to modify the unique polysaccharide, alternan. Spores from these isolates germinated in medium containing alternan and reduced the apparent molecular weight of alternan as determined by high-performance size exclusion chromatography and viscometry. However, the fungi exhibited limited growth on alternan and did not consume the substrate. The rheological properties of the modified alternan resembled those of commercial gum arabic. Thus, treatment of native alternan with spores from these Penicillium spp. strains constitutes a simple bioconversion method to quantitatively produce novel and potentially useful modified alternan. Journal of Industrial Microbiology & Biotechnology (2002) 29, 177–180 doi:10.1038/sj.jim.7000272 Received 14 February 2002/ Accepted in revised form 13 May 2002     

Proceedings: Freezing and freeze-drying of Spirulina platensis

A species of blue-green alga, Spirulina platensis, is extremely susceptible to freezing and drying. However, young cells grown autotrophically with a high intensity of light were resistant to freeze-thawing if the rate of temperature change in the operation was in the range of 20–50 °C/min. Several amino acids, gum arabic, and gelatin were effective in protecting cells from injury caused by freezing.In the case of drying only gum arabic and gelatin could protect cells from injury. The gum arabic-plug method of freeze-drying was shown to be the most suitable method for the maintenance of viability in this alga.The freeze-thawed or freeze-dried cells grew to form abnormally long cells after a period of long lag in the first stage of transfer.     

Control of Root-knot Nematode with Formulations of the Nematode-Trapping FungusArthrobotrys dactyloides

Arthrobotrys dactyloidesgrew readily in shaken flasks containing glucose corn steep powder and 8–10 g dry wt of fungal biomass/liter medium was usually produced in 5–6 days. However, it was difficult to convert this biomass into a viable, granulated product suitable for commercial use in biological control. Formulations prepared using kaolin and vermiculite as carriers and gum arabic as a binder showed poor viability when biomass was harvested from liquid culture, mixed with formulation ingredients, granulated, and then dried to a moisture content of less than 5%. Inclusion of a solid-phase incubation step following granulation and prior to drying (incubation of moist granules for 3 days at 25°C in a sterile plastic bag aerated with sterile air) markedly improved biological activity. When granules produced in this manner were placed on a glass slide in field soil, hyphae proliferated from granules and always produced traps. Seven experiments in soil microcosms showed that formulations which had been subjected to solid phase incubation prior to drying consistently reduced numbers ofMeloidogyne javanicajuveniles by more than 90%. In seven glasshouse experiments in which field soils were treated with granules (10 g/liter) and planted to tomatoes, the number of galls induced by the nematode was reduced by 57–96%.