Chemical Control of Basal Stem Rot Disease of Tomato (Lycopersicon esculentum Mill.) in Northern Nigeria

Six fungicides (Aatopam-N, Aldrex T, Calixin M, PCNB, captan and captafol) were evaluated at 200 mg a.i.l^?1 for their effectiveness in reducing basal stem rot disease incited by Sclerotium rolfsii on tomato in pre- and post-inoculation soil drenches in the glasshouse. The results showed that only PCNB effectively reduced disease severity when applied to soil 10 days before inoculation. Of the two application methods only pre-inoculation soil drenching with the fungicides was efficacious in reducing disease severity. In field trials conducted in Samaru with Aldrex T, captan and PCNB, only PCNB was effective in combating the severity of the disease. It reduced the disease by about 88% in one trial.     

Biological Control of Carrot Black Rot

Diseased carrot seeds were treated with selected micro-organisms isolated from soils, carrot seeds and tap roots. The effects of those antagonists on the control of Alternaria radicina were evaluated by growing-on tests on water agar, filter paper, vermiculite and in a potting medium (BVB no. 4). The germination percentage, emergence percentage and the disease severity of those carrot seeds treated with Burkholderia (Pseudomonas) cepacia no.229 were significantly (P=0.05) differed from the non-treated seeds and the seed treated with other antagonists. The effects of B. cepacia no.229 in promoting seed emergence and controlling disease were as good as those seeds treated with iprodione (100 p.p.m.). Black rot lesions on carrot tap roots were significantly reduced (P=0.05) in size when roots were treated with B. cepacia no 229 or Bacillus amyloliquefaciens no. 224 compared to the nontreated roots. Also, B. cepacia no. 229 significantly (P=0.05) reduced black rot on the foliage of carrot compared to check.     

Factors Affecting Biological Control of Sclerotinia sclerotiorum by Fungal Antagonists

Studies were conducted to determine the effects of soil moisture (9, 16 or 24% w/w) and temperature (5, 15, 20 or 25°C) on the control of sclerotia of Sclerotinia sclerotiorum by five fungal agents in sterile and natural field soil. All five biocontrol agents were effective in reducing the survival of sclerotia of S. sclerotiorum in sterile soil under dry (9% moisture) or wet (24% moisture) conditions at 20°C, but only Coniothyrium minitans was effective in natural soil. Coniothyrium minitans was the most effective in reducing sclerotial viability at the temperature range of 15–25°C. Trichoderma virens was effective against sclerotia of S. sclerotiorum to a lesser extent than C. minitans , and in non-autoclaved soil, it performed best at 25°C. Although Epicoccum purpurascens , Talaromyces flavus and Trichothecium roseum were effective against sclerotia of S. sclerotiorum in some instances, they were less effective than C. minitans and T. virens . Sclerotia of S. sclerotiorum conditioned for myceliogenic germination were more vulnerable to attack by the biocontrol agents than dormant sclerotia. The implications are discussed with respect to enhancement of biological control of crop diseases caused by S. sclerotiorum in different geographic regions.     

季也蒙假丝酵母对采后桃果实软腐病的抑制效果

The biocontrol capability of Candida guilliermondii (Cast) Langeroret Guerra against Rhizopus stolonifer (Ehrenb.ex Fr.) Vuill. postharvest rot of peach fruits was studied in vitro and in vivo under different storage temperatures. C. guilliermondii at 5.0×108 CFU (colony-forming unit)/mL of washed cells provided complete control of 5×104 spores /mL of R. stolonifer during storage at 25 ℃ for 4 d, 15 ℃ for 7 d and 3℃ for 30 d. Temperature had no significant effect on the biocontrol efficacy. Antagonist population increased 45.6, 34.4 and 33.1 times per site at 25℃, 15℃ and 3℃ for 3, 3 and 7 d,respectively, then the population stabilized for the remaining storage period. Cell-free culture filtrate of C. guilliermondii was not effective in preventing decay and resulted in even greater lesion diameter than those of sterile distilled water at 3 ℃.These results showed that competition for nutrient, not antibiotic production, plays a major role in the biocontrol capability of C. guilliermondii against rhizopus rot of peach fruits. As the interval between wounding and inoculation with the pathogen increased from 0 to 72 h, susceptibility of wounds to decay by R. stolonifer decreased from 100% of 0 h to 5% of 4 h and 0% of 24 h, then increased to 10% of 48 h and 40% of 72 h.     

Biological Control of Macrophomina phaseolina Charcoal Rot of Sunflower and Mung Bean

Infection by Macrophonina phaseolina was substantially reduced following treatment of sunflower and mungbean seeds with Trichoderma harzianum, Gliocladium virens, Paecilomyces lilacinus or Streptomyces sp. which gave promising control of charcoal rot disease. Treatment of mungbean seeds with Rhizobium meliloti also gave good disease control.     

Postharvest Biological Control of Potato Sprouting by Fusarium Dry Rot Suppressive Bacteria

Chemical sprout inhibitors are applied to over 50% of the potato harvest to extend storage time. In the U.S.A., CIPC (1-methylethyl-3-chlorophenylcarbamate) is the only synthetic chemical registered for postharvest sprout control of stored potatoes, and it is the most widely used sprout inhibitor world-wide. Due to environmental and health safety concerns, the use of CIPC has become more restricted, and alternative sprout control methods are sought. Six bacteria strains, exhibiting superior dry rot suppressiveness in previous research, were grown in two different liquid culture media and sprayed on Russet Burbank potatoes. In growth chamber and pilot experiments repeated at two storage sites in two successive years, all six isolates demonstrated significant sprout control capabilities when applied after growth on at least one of the culture media supplied. Of the six strains tested, Pseudomonas fluorescens bv.V S11:P:12 and two strains of Enterobacter sp., S11:T:07 and S11:P:08, exhibited highest relative performance levels with sprout control being statistically similar to that of 16.6 ppm CIPC thermal fog after 4-5 months storage.     

Biological and Integrated Control of Botrytis Bunch Rot of Grape UsingTrichodermaspp.

Field trials were carried out in upstate New York in 1990, 1992, 1993, and 1994 and in Chile in 1992–1993 and 1993–1994 in order to evaluate the ability of various strains ofTrichodermaspp. to control bunch rot of grape, to assess the compatibility and possible additive effects of selected biocontrol fungi and dicarboximide fungicides, and to determine factors affecting biocontrol efficacy. In 1990, three strains ofTrichodermaspp. were evaluated for their biocontrol ability, and all provided significant control ofBotrytis cinerea.As few as two late applications of the biocontrol fungi were nearly as effective as up to five applications throughout bloom and fruit development. Trials in New York in 1992 and in Chile in 1992–1993 indicated thatTrichoderma harzianumcould replace some applications of iprodione or vinclozolin with little reduction in efficacy. In New York in 1993, we found that applications ofT. harzianumat bloom and early fruit development followed by a tank-mix application ofT. harzianumand half rates of iprodione gave extremely effective control of bunch rot. In 1994, less effective control was obtained than in earlier years. Addition of a nutritive adhesive (Pelgel, a mixture of carboxymethyl cellulose and gum arabic) applied with the biocontrol agent tended to improve results. Thus, biological control of bunch rot of grape withT. harzianumcan be an effective method of management of this disease.     

Biological Control of Chickpea Collar Rot by Co-inoculation of Antagonistic Bacteria and Compatible Rhizobia

Two hundred and seven bacteria were isolated from composts and macrofauna and screened for plant growth promoting and antagonistic traits. Seven of the 207 isolates showed antagonistic activity against Sclerotium rolfsii in plate culture. Inhibition of S. rolfsii by the bacterial isolates ranged between 61 and 84%. Two of the seven isolates were Bacillus sp. and rest belonged to Pseudomonas sp. Two isolates, Pseudomonas sp. CDB 35 and Pseudomonas sp. BWB 21 was compatible with chickpea Rhizobium sp. IC 59 and IC 76 in plate culture conditions. Increase in plant biomass (dry weight) ranged between 18 and 30% on application of these bacteria by seed coating and seed priming methods. However, by seed-priming there was an increase in plant biomass by 5–7% compared to seed coating. Number of nodules and the nodule weight was similar by both seed coating and seed priming methods. Disease incidence was reduced up to 47% in treatments where captan (fungicide) or antagonistic Pseudomonas sp. CDB 35 was applied. Increase in shoot weight was 36% by seed coating with Rhizobium sp. IC 59 and Pseudomonas sp. CDB 35 when compared to captan application. Whereas by seed priming with IC 59 and CDB 35 increased shoot weight by 3 and 39% increase in nodulation was observed.     

Derivation of Airway Basal Stem Cells from Human Pluripotent Stem Cells

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地被菊不同基质的扦插对比试验

研究不同基质对地被菊扦插繁殖的影响。采用五组基质做对比试验,结果表明各组的生根率均在90％以上。基质对其生根率和生根条数的影响差异不显著。根系质量生长相对较好的基质配比为蛭石：腐殖质土（1：3）,园土：细沙：有机肥（7：2：1）和园土：腐殖质土（4：1）。试验证明在银川地被菊的扦插成活率高,可推广应用于生产实践。     

Biological Control of Phytophthora Root Rot of Pepper Using Trichoderma harzianum and Streptomyces rochei in Combination

A combination of two compatible micro‐organisms, Trichoderma harzianum and Streptomyces rochei, both antagonistic to the pathogen Phytophthora capsici, was used to control root rot in pepper. The population of the pathogen in soil was reduced by 75% as a result. Vegetative growth of the mycelium of P. capsici was inhibited in vitro on the second day after P. capsici and T. harzianum were placed on the opposite sides of the same Petri plate. Trichoderma harzianum was capable of not only arresting the spread of the pathogen from a distance, but also after invading the whole surface of the pathogen colony, sporulating over it. Scanning electron microscopy showed the hyphae of P. capsici surrounded by those of T. harzianum, their subsequent disintegration, and the eventual suppression of the pathogen's growth. Streptomyces rochei produced a zone of inhibition, from which was obtained a compound with antioomycete property secreted by the bacteria. When purified by high‐pressure liquid chromatography, this compound was identified as 1‐propanone, 1‐(4‐chlorophenyl), which seems to be one of the principal compounds involved in the antagonism. A formulation was prepared that maintained the compound's capacity to inhibit growth of the pathogen for up to 2 years when stored at room temperature in the laboratory on a mixture of plantation soil and vermiculite. The two antagonists, added as a compound formulation, were effective at pH from 3.5 to 5.6 at 23–30°C. The optimal dose of the antagonists in the compound formulation was 3.5 × 10⁸ spores/ml of T. harzianum and 1.0 × 10⁹ FCU/ml of S. rochei. This is the first report of a compound biocontrol formulation of these two antagonists with a potential to control root rot caused by P. capsici.     

Studies on Biological Control of Postharvest Rot in Yams (Dioscorea spp.) using Trichoderma viride

From in vitro and in vivo screening tests for antagonism by isolates of Trichoderma against postharvest pathogens of yams (Dioscorea spp.), an isolate of Trichoderma viride Pers. ex S.F. Gray was selected as the most promising candidate for the biocontrol of postharvest rot of yams. Inoculation of white yam (Dioscorea rotundata Poir.) with conidiaspores of T. viride and subsequent storage of the tubers under the ambient environment conditions of a traditional yam barn, resulted in a drastic reduction in the frequency of occurrence of the normal tuber surface mycoflora over a 4‐month (December‐April) storage period. Trichoderma viride on the other hand, maintained a high frequency of occurrence during the same period. Furthermore, whereas up to 52.0%) rot was found among groups of tubers that were artificially inoculated with the postharvest pathogens of yams, Aspergillus niger Van Tiegh., Botryodiplodia theobromae Pat. or Penicillium oxalicum Currie and Thom, and also the group that was not inoculated with any organism (control), among groups of tubers that were inoculated with T. viride the rot was either totally suppressed or only a low percentage of rot occurred. The significance of the findings is discussed in relation to yam storage especially by farmers with limited resources.     

Effect of Brown Stem Rot on Water Relations of Soybean

To investigate the effects of brown stem rot, a vascular disease of soybean (Glycine max) induced by Phialophora gregata, on the water relations of diseased plants, stems of greenhouse-grown plants of susceptible (Pride B216) and resistant (BSR 201) cultivars were injected with the pathogen at vegetative growth stage VI. Plants of both cultivars developed internal stem browning, but those of Pride B216 developed more severe symptoms of water stress (reduced leaf water potential and stem conductance). Inoculated plants of both cultivars also had reduced stem conductance and increased stomatal conductance and transpiration. Disease-related water stress can be attributed to the combined effects of reduced stem conductance and increased water loss resulting from increased stomatal conductance.     

Evaluation of a Peroxyacetic Acid Disinfectant in Hot-water Treatment for the Control of Basal Rot (Fusarium oxysporum f. sp. narcissi) and Stem Nematode (Ditylenchus dipsaci) in Narcissus

Formaldehyde is used routinely in the hot-water treatment (HWT) of narcissus bulbs for the control of stem nematode (Ditylenchus dipsaci) and basal rot (caused by Fusarium oxysporum f.sp. narcissi). Formaldehyde is unpleasant for operators to use, and does not kill all of the thick-walled chlamydospores of F. oxysporum and so less hazardous but more effective materials are being sought. Peroxyacetic acid (as Jet 5, a commercial disinfectant containing 5% peroxyacetic acid) was evaluated in vitro and in a field trial as a possible alternative to formaldehyde. In laboratory studies, peroxyacetic acid (as 1% Jet 5) was as effective as formaldehyde (as 0.5% commercial formalin containing 38 to 40% formaldehyde) in killing free-swimming stem nematodes and nematodes in the wool stage. Peroxyacetic acid (as 0.5% Jet 5) killed F. oxysporum chlamydospores within 1 h, whereas total kill was not achieved with formaldehyde (concentration as above) after 4 h. In a 2 year field trial, there was no evidence of detrimental effects on a healthy narcissus stock due to using peroxyacetic acid. In an infested, diseased stock, bulbs were virtually destroyed by stem nematode within 2 years when HWT was not given. The greatest reduction in nematode symptoms, and the highest bulb yields, were found when formaldehyde or the higher rates of peroxyacetic acid were used in combination with thiabendazole.