Effect of Chlorine on Giardia lamblia Cyst Viability

The effect of chlorine concentration on Giardia lamblia cyst viability was tested under a variety of conditions. The ability of Giardia cysts to undergo excystation was used as the criterion of viability. The experimental variables employed included temperature (25, 15, and 5°C), pH (6, 7, and 8), chlorine-cyst contact time (10, 30, and 60 min), and chlorine concentration (1 to 8 mg/liter). In the pH range studied, cyst survival generally was observed to increase as buffer pH increased. Water temperature coupled with chlorination proved to be important in cyst survival. Results of these experiments at the three temperatures studied can be summarized as follows: at 25°C, exposure to 1.5 mg/liter for 10 min killed all cysts at pH 6, 7, and 8. At 15°C, 2.5 mg of chlorine per liter for 10 min killed all cysts at pH 6, but at pH 7 and 8 small numbers of cysts remained viable after 30 min but not after 60 min. At 5°C, 1 mg of chlorine per liter for 60 min failed to kill all the cysts at any pH tested. At this temperature, 2 mg of chlorine per liter killed all cysts after 60 min at pH 6 and 7, but not at pH 8. A chlorine concentration of 4 mg/liter killed all the cysts at all three pH values after 60 min, but not after 30 min. A chlorine concentration of 8 mg/liter killed all Giardia cysts at pH 6 and 7 after contact for 10 min, and at pH 8 after 30 min. This study points up the role of temperature, pH, and chlorine demand in the halogen treatment of drinking water to destroy cysts. It also raises an epidemiological problem, namely: low water temperatures, where killing of Giardia requires relatively high chlorine concentrations and long contact times, are (i) to be expected in many areas where epidemic waterborne giardiasis has been reported and (ii) particularly conducive to the long-term survival of Giardia cysts.     

Reproductive and Damage Potential of Ditylenchus destructor on Six Peanut Cultivars

Commercial peanut cultivars were evaluated for host suitability and sensitivity to Ditylenchus destructor. All cultivars were susceptible. Approximately 94% of the final population were in the pods. Highest Pf occurred at harvest on early maturing cultivars. Damage occurred on four of six cuttivars at Pi = 100/3 liters of soil and all six cultivars at Pi = 1,000. Norden and Selmani were the most susceptible cultivars. Sellie was the most tolerant and highest yielding cultivar. This cultivar may be the most profitable one for growers.     

Mycoflora of developing peanut pods in Oklahoma

Starr and Argentine peanut cultivars were grown in soil fungicide treated irrigated and non-irrigated plots in a 2 year study designed to determine possible differences in invasion of developing seed pods byAspergillus flavus and other mycoflora. Many genera and species were isolated from whole pods and half shells throughout each season. Fungi were seldom isolated from kernels. No significant differences in populations between fungicide treatments, irrigation, or cultivars were found. Significant shifts in frequency of isolation of dominant genera (Fusarium andPenicillium) occurred during 1965 and 1966.Trichoderma viride, a minor component of the population at the first sampling in 1966, became a sub-dominant member by the last sampling. The reverse was true withA. niger. Several species of fungi, never before reported as occurring in peanut pods, were found in pods in this study:Actinomucor elegans, A. sclerotiorum, Sordaria fimicola, S. humana, andSporormia australis.Journal Article No. 1914, Oklahoma State University, Agricultural Experiment Station, Stillwater, Oklahoma.     

Effects of Switchgrass (Panicum virgatum) Rotations with Peanut (Arachis hypogaea L.) on Nematode Populations and Soil Microflora

A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut without nematicide application or peanut without nematicide following 2 years of cotton. Peanut yield did not differ among rotations in either sample year. Effects of crop rotation on the microbial community structure associated with peanut were examined using indices for diversity, richness, and similarity derived from culture-based analyses. Continuous peanut supported a distinctly different rhizosphere bacterial microflora compared to peanut following 1 year of switchgrass, or continuous switchgrass. Richness and diversity indices for continuous peanut rhizosphere and geocarposphere were not consistently different from peanut following switchgrass, but always differed in the specific genera present. These shifts in community structure were associated with changes in parasitic nematode populations.     

Persistence and Suppressiveness of Pasteuria penetrans to Meloidogyne arenaria Race

The long-term persistence and suppressiveness of Pasteuria penetrans against Meloidogyne arenaria race 1 were investigated in a formerly root-knot nematode suppressive site following 9 years of continuous cultivation of three treatments and 4 years of continuous peanut. The three treatments were two M. arenaria race 1 nonhost crops, bahiagrass (Paspalum notatum cv. Pensacola var. Tifton 9), rhizomal peanut (Arachis glabrata cv. Florigraze), and weed fallow. Two root-knot nematode susceptible weeds commonly observed in weed fallow plots were hairy indigo (Indigofera hirsuta) and alyce clover (Alysicarpus vaginalis). The percentage of J2 with endospores attached reached the highest level of 87% in 2000 in weed fallow, and 63% and 53% in 2002 in bahiagrass and rhizomal peanut, respectively. The percentage of endospore-filled females extracted from peanut roots grown in weed fallow plots increased from nondetectable in 1999 to 56% in 2002, whereas the percentages in bahiagrass and rhizomal peanut plots were 41% and 16%, respectively. Over 4 years, however, there was no strong evidence that endospores densities reached suppressive levels because peanut roots, pods, and pegs were heavily galled, and yields were suppressed. This might be attributed to the discovery of M. javanica infecting peanut in this field in early autumn 2001. A laboratory test confirmed that although the P. penetrans isolate specific to M. arenaria attached to M. javanica J2, no development occurred. In summary, P. penetrans increased on M. arenaria over a 4-year period, but apparently because of infection of M. javanica on peanut at the field site root-knot disease was not suppressed. This was confirmed by a suppressive soil test that showed a higher level of soil suppressiveness than occurred in the field (P ≤ 0.01).     

Criconemoides ornatus Parasitic on Peanuts

Roots, pods, and pegs of ''Argentine'' and ''Starr'' peanut cultivars inoculated with Criconemoides ornatus were severely discolored with brown necrotic lesions. Nematodes were attached to roots, pods, and pegs often in large numbers. Small necrotic lesions were often superficial, but necrosis in large lesions usually extended deep into the tissues. Lesions were present on roots of all ages. Many lateral root primordia, and young roots were killed resulting in reduced numbers of laterals. Pod yields from nematode infected plants were reduced about one-half.     

Oxygen and the Infectivity of Romanomermis culicivorax

The effects on itffectivity by preparasitic Romanomermis culicivorax resulting from four exposure times to four concentrations of oxygen at three temperatures were studied . Low oxygen (1.8 and 3.1 mg /liter) slowed losses of infectivity. Losses of infectivity were similar under aerobic (6 mg /liter) and microaerobic (0.4 mg /liter) conditions for the first 24 h but thereafter were slower in the microaerobic group. N interactions between temperature and oxygen were found over the ranges tested (15-27 C; 0.4-6.0 mg /liter).     

Evaluation of various flocculants for the recovery of algal biomass grown on pig-waste

Laboratory experiments were conducted to compare the effectiveness of chitosan (by-product derived from shrimp and crab shells), Zetag 63 and CF 400 (hydrolyzed polyacrylamide) as flocculants to concentrate a mixed culture of chlorophyceae dominated by Chlorella sp. The algae were grown in a high-rate algal pond (HRAP) fed with dilute pig-waste. Algal sedimentation rates were measured in the laboratory.For a pH range of 6·0–9·0, flocculation efficiency of 95–100% was obtained at 20 mg/liter chitosan and 5 mg/liter Zetag 63. The optimum range of initial biomass concentration for maximum algal recovery was found to be 100–200 mg dry weight algae/liter.     

Population Dynamics of Ditylenchus destructor on Peanut

The population development of Ditylenchus destructor in the roots, pegs, hulls, and seeds of eight peanut (Arachis hypogaea) genotypes was studied in the greenhouse. Although all genotypes tested were good hosts for D. destructor, differences in host suitability were observed. Invasion of the plant parts by Ditylenchus destructor proceeded more slowly in genotypes with long growth periods. During the second half of the growth period of these genotypes, D. destructor populations emigrated from the hulls and seeds into the soil but reinfected the pods after a few weeks. The genotypes with the longest growth periods supported the highest number of nematodes when each genotype was harvested at its usual harvest time. The long-season genotypes supported low numbers of nematodes when harvested before crop maturity.     

Relationship between Meloidogyne arenaria and Aflatoxin Contamination in Peanut

Damaged and developing kernels of peanut (Arachis hypogaea) are susceptible to colonization by fungi in the Aspergillus flavus group which, under certain conditions, produces aflatoxins prior to harvest. Our objective was to determine whether infection of peanut roots and pods by Meloidogyne arenaria increases aflatoxin contamination of the kernels when peanut is subjected to drought stress. The experiment was a completely randomized 2-x-2 factorial with 6 replicates/treatment. The treatment factors were nematodes (plus and minus M. arenaria) and fungus (plus and minus A. flavus inoculum). The experiment was conducted in 2001 and 2002 in microplots under an automatic rain-out shelter. In treatments where A. flavus inoculum was added, aflatoxin concentrations were high (> 1,000 ppb) and not affected by nematode infection; in treatments without added fungal inoculum, aflatoxin concentrations were greater (P ≤ 0.05) in kernels from nematode-infected plants (1,190 ppb) than in kernels from uninfected plants (79 ppb). There was also an increase in aflatoxin contamination of kernels with increasing pod galling (r² = 0.83 in 2001, r² = 0.43 in 2002; P ≤ 0.04). Colonization of kernels by A. flavus increased with increasing pod galling (r² = 0.18; P = 0.04) in 2001 but not in 2002. Root-knot nematodes may have a greater role in enhancing aflatoxin contamination of peanut when conditions are not optimal for growth and aflatoxin production by fungi in the A. flavus group.     

Histological Studies of Ditylenchus africanus Within Peanut Pods

Ditylenchus africanus entered the immature pegs and pods of peanut (Arachis hypogaea cv. Sellie) at the peg-connection and subsequently invaded the parenchymatous regions of the hull exocarp and endocarp, and eventually the seed testa. The nematode caused malformations of the cells of infected tissues, cell wall breakage, and cell collapse. The damage appeared to be due to enzymatic activity. In some testae the entire parenchyma region, which aids in protection of the seed, was destroyed. In immature pods, the nematodes moved across the fibrous region of the mesocarp into the hull endocarp. In mature pods, however, the fibrous mesocarp of the hull was lignified and apparently was a barrier to penetration of the inner pod tissues. In late-harvested pods, increased numbers of eggs and anhydrobiotes were found in the hull tissues, and eggs in the seed testa, suggesting the onset of winter survival mechanisms of the nematode.     

Role of Nematodes and Soil-borne Fungi in Cotton Stunt

The nematodes, Pratylenchus brachyurus, Trichodorus christiei, and T. porosus and the soil-borne fungi, Rhizoctonia solani, Pythium debaryanum, P. irregulare, P. ultimum, and Fusarium spp. were the pathogens most frequently found in the roots and rhizosphere of field-grown cotton (Gossypium hirsutum) showing "stunt" symptoms. Field-plot application of the nematicide D-D (l,2-dichloropropane, 1,3-dichloropropene) at 373.4 liter/ha (40 gal/A) significantly increased plant growth and yield. A fungicidal mixture of Dexon (p-dimethylaminobenzenediazo sodium sulfonate at 23.5 kg/ha (2l lb/A) and Terraclor (pentachloronitrobenzene at 25.2 kg/ha (22.5 lb/A) was phytotoxic, but combined nematicide/fungicide treatments were not. Greenhouse temperature-tank experiments in soils from two locations showed significantly improved root and shoot growth following methyl bromide fumigation at both 25 C and 18 C and more severe "stunt" at the lower temperature.     

Damage Functions for Three Meloidogyne Species on Arachis hypogaea in Texas

The yield response of Florunner peanut to different initial population (Pi) densities of Meloidogyne arenaria, M. javanica, and an undescribed Meloidogyne species (isolate 93-13a) was determined in microplots in 1995 and 1996. Seven Pi''s (0, 0.5, 1, 5, 10, 50, and 100 eggs and J2/500 cm³ soil) were used for each Meloidogyne species in both years. The three species reproduced abundantly on Florunner in both years. In 1995, mean reproduction differed among the three species; mean Rf values were 10,253 for isolate 93-13, 4,256 for M. arenaria, and 513 for M. javanica. In 1996, the reproduction of M. arenaria (mean Rf = 7,820) and isolate 93-13a (mean Rf = 7,506) were similar, and both had greater reproduction on peanut than did M. javanica (mean Rf = 2,325). All three nematode species caused root and pod galling, and a positive relationship was observed between Pi and the percentage of pods galled. Meloidogyne arenaria caused a higher percentage of pod galling than did M. javanica or isolate 93-13a. A negative linear relationship between log₁₀ (Pi + 1) and pod yield was observed for all three nematode species each year. The yield response slopes were similar except for that of M. javanica, which was less negative than that of isolate 93-13a in 1995, and less negative than that of M. arenaria and isolate 93-13a in 1996.     

Solid-state fermentation production of tetracycline by <Emphasis Type="Italic">Streptomyces</Emphasis> strains using some agricultural wastes as substrate

The ability of Streptomyces sp. OXCI, S. rimosus NRRL B2659, S. rimosus NRRL B2234, S. alboflavus NRRL B1273 S. aureofaciens NRRL B2183 and S. vendagensis ATCC 25507 to produce tetracycline using some local agricultural wastes as solid state media, were assessed. The wastes employed include peanut (groundnut) shells, corncob, corn pomace and cassava peels. Bacillus subtilis ATCC 6633 was used to assay antimicrobial activity. All the strains produced tetracycline in a solid-state fermentation process containing peanut (groundnut) as the carbohydrate source. Streptomyces sp. OXC1 had the highest ability for tetracycline production with peanut shells as the substrate in solid fermentation (13.18 mg/g), followed by S. vendagensis ATCC 25507 (11.08 mg/g), S.rimosus NRRL B1679 (8.46 mg/g), S. alboflavus NRRL B1273 (7.59 mg/g), S. rimosus NRRL B2234 (6.37 mg/g), S. aureofaciens NRRL B2183 (4.27 mg/g). Peanut (groundnut) shells were the most effective substrate (4.36 mg/g) followed by corncob (2.64 mg/g), cassava peels (2.16 mg/g) and corn pomace (1.99 mg/g). The composition of the peanut (groundnut) shell medium optimal for tetracycline production were peanut shells 100 g, organic nitrogen (peanut meal) 10 g, (NH ₄)₂ SO₄ 1 g, KH₂ PO ₄ 0.5 g, CaCO₃ > 0.5 g, NaCl 0.5 g, MgSO₄ · 7H₂ O 0.5 g, soluble starch 10 g, peanut oil 0.25 ml with initial moisture content of 65–68%, and initial pH 5.3–6.3. Substrate (1 g dry weight) was inoculated with 1.0 × 10 ⁸ conidia per ml and incubated at 28–31 °C for 5–7 days, producing 13.18 mg/g of total tetracycline. Tetracycline detection started on day 3 and attained its maximum level on day 5.     

Relative Damage Functions and Reproductive Potentials of Meloidogyne arenaria and M. hapla on Peanut

The reproductive potential and damage functions for Meloidogyne hapla and M. arenaria race 1 on Virginia-type peanuts (Arachis hypogaea cv. Florigiant) were determined over 2 years in microplot experiments in North Carolina. Peanut yield suppression and damage to pods as a result of galling were greatest in response to M. arenaria (P = 0.01). Damage functions for the two species were adequately described by the quadratic models: yield (g/plot) = 398 - 17.1 (log₁₀[Pi + 1]) - 17.0(log₁₀[Pi + 1])²; (R² = 0.83, P = 0.0001) for M. arenaria; and yield = 388 - 10.2(log₁₀[Pi + 1]) - 7.5(log₁₀[Pi + 1])², (R² = 0.30, P = 0.0001) for M. hapla. Both species caused galling on pods, but this was more severe in response to M. arenaria. Reproduction of M. arenaria race 1 was greater than M. hapla on peanut, which accounts in part for the more severe pod galling. Peanut was an excellent host for both M. arenaria race 1 and for M. hapla, but reproduction by M. hapla was more variable.     

Destruction of Toxic Fungi with Low Concentrations of Methyl Bromide

Aspergillus parasiticus and Penicillium rubrum spores at the level of 10(4) to 10(5) / g were completely killed by prolonged exposure to 30 to 45 mg of methyl bromide per liter.     

Bahiagrass,Corn, Cotton Rotations,and Pesticides for Managing Nematodes,Diseases, and Insects on Peanut

Florunner peanut was grown after 1 and 2 years of Tifton 9 bahiagrass, corn, cotton, and continuous peanut as whole-plots. Pesticide treatments aldicarb (3.4 kg a.i./ha), flutolanil (1.7 kg a.i./ha), aldicarb + flutolanil, and untreated (control) were sub-plots. Numbers of Meloidogyne arenaria second-stage juveniles in the soil and root-gall indices of peanut at harvest were consistently lower in plots treated with aldicarb and aldicarb + flutolanil than in flutolanil-treated and untreated plots. Percentages of peanut leaflets damaged by thrips and leafhoppers were consistently greater in flutolaniltreated and untreated plots than in plots treated with aldicarb or aldicarb + flutolanil but not affected by cropping sequences. Incidence of southern stem rot was moderate to high for all chemical treatments except those that included flutolanil. Stem rot loci were low in peanut following 2 years of bahiagrass, intermediate following 2 years of corn or cotton, and highest in continuous peanut. Rhizoctonia limb rot was more severe in the peanut monoculture than in peanut following 2 years of bahiagrass, corn, or cotton. Flutolanil alone or combined with aldicarb suppressed limb rot compared with aldicarb-treated and untreated plots. Peanut pod yields were 4,186 kg/ha from aldicarb + flutolanil-treated plots, 3,627 kg/ha from aldicarb-treated plots, 3,426 kg/ha from flutolanil-treated plots, and 3,056 kg/ha from untreated plots. Yields of peanut following 2 years of bahiagrass, corn, and cotton were 29% to 33% higher than yield of monocultured peanut.     

Production of Higher Alcohols During Indonesian Tapé Ketan Fermentation

A study was made of the higher alcohols (fusel oils) produced during the Indonesian tapé ketan fermentation using Amylomyces rouxii as the principal mold, alone or in combination with yeasts belonging to genera commonly found in the tapé ketan fermentation (Endomycopsis, Candida, and Hansenula). Total fusel oils increased with length of fermentation. Fusel oils detected in the product distillate included isobutanol and isoamyl and active amyl alcohols. No n-propanol was detected. Isobutanol and isoamyl alcohols were formed in the largest amounts. A. rouxii alone produced nearly the same quantity of fusel oils (total production, 275 mg/liter at 192 h) as it did in combination with Endomycopsis burtonii (total production, 292 mg/liter at 192 h).A. rouxii and Endomycopsis fibuliger produced fusel oils totaling 72 mg/liter at 32 h and 558 mg/liter at 192 h. A. rouxii in combination with Candida yeasts produced somewhat more fusel oils, ranging from 590 to 618 mg/liter at 192 h. A. rouxii in combination with Hansenula yeasts produced the least fusel oils, totaling 143 to 248 mg/liter at 192 h. During the first 36 h, production of fusel oils was higher at 30 and 35°C than at 25°C. At 48 h fusel oil production was slightly higher at 30°C than at 35°C. Beyond 48 h, production of fusel oils was higher at 25°C. A. rouxii in combination with Hansenula anomala and Hansenula subpelliculosa produced considerable ethyl acetate, ranging from 145 to 199 mg/liter at 36 h and 354 to 369 mg/liter at 192 h.     

Factors Affecting Oxidation of Thiosalts by Thiobacilli

The effects of temperature, initial pH, and the concentrations of ammonium, phosphate, and heavy metals on the oxidation of thiosalts by an authentic strain of Thiobacillus thiooxidans (ATCC 8085) and by a mixed culture isolated from a base metal-processing mill effluent pond were studied. The optimum temperature was 30°C and the optimum initial pH was 3.75 for both cultures using thiosulfate and for the mixed culture using tetrathionate. T. thiooxidans ATCC 8085 did not oxidize tetrathionate. For a thiosalt concentration of 2,000 ppm (2,000 mg/liter), maximal rates of destruction occurred at concentrations of ammonium ion above 2 mg/liter and in the presence of 1 mg of phosphate per liter. Under optimal conditions, the rate of thiosulfate oxidation by the pure culture was 55 ± 3 mg/liter per h; the mixed culture oxidized thiosulfate at the rate of 40 ± 1 mg/liter per h and tetrathionate at the rate of 50 ± 2 mg/liter per h. Metal ions caused normal inhibition kinetics in the oxidation of thiosulfate by T. thiooxidans ATCC 8085. K_i values were calculated for cadmium (16 mg/liter), copper (0.46 mg/liter), lead (2 mg/liter), silver (3.1 mg/liter), and zinc (33 mg/liter). Only a slight additive effect was apparent in the presence of all of these metal ions. The mixed culture of thiosalt-oxidizing bacteria was less sensitive to heavy metal inhibition; the order of inhibition of thiosulfate oxidation was Cd < Zn < Pb < Ag < Cu, and that of tetrathionate oxidation was Zn < Cd < Pb < Ag < Cu.