Fusarium Oxysporum Schl Research Articles

Isolation, Purification and Pathogenicity Assessment of Fusarium oxysporum Schl. f.sp. ciceris Inciting Wilt Disease in Chickpea

The present study was conducted during rabi (November–March, 2022–23) at the Department of Plant Pathology and Central Instrumentation Cell, College of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India to isolate, purify and pathogenicity assessment of Fusarium oxysporum Schl. f.sp. ciceris inciting wilt disease in chickpea. The pathogen was isolated from infected chickpea and purified, with its cultural and morphological characteristics utilized for identification. The analysis revealed that pathogen grown on potato dextrose agar media exhibited traits consistent with Fusarium oxysporum Schl. f.sp. ciceris, appearing as mycelium colour, texture, pigmentation, type and speed of growth as cultural characteristics and Fusarium oxysporum Schl. f.sp. ciceris as possessing macroconidia, microconidia and chlamydospore as morphological characteristics. Furthermore, a pathogenicity test was conducted on the chickpea cultivar JG-62, cultivated in pots under controlled conditions within a net house was successfully satisfying Koch’s postulates. Because of its great nutritious content, chickpeas have risen to prominence. where it plays a significant role in ensuring food security and sustainability. However, wilt disease in chickpea remains a persistent threat, leading to substantial losses in both quantity and quality. To address this issue the investigation provided valuable insights into understanding the pathogen, thereby contributing to the development of cost-effective solutions for managing wilt disease in chickpea which helps in increasing crop yield to the chickpea growing farmers of Telangana.

Biochemical mechanisms preventing wilting under grafting: a case study on pumpkin rootstock grafting to wax gourd.

Wax gourd wilt is a devastating fungal disease caused by a specialized form of Fusarium oxysporum Schl. f. sp. benincasae (FOB), which severely restricts the development of the wax gourd industry. Resistant rootstock pumpkin grafting is often used to prevent and control wax gourd wilt. The "Haizhan 1" pumpkin has the characteristic of high resistance to wilt, but the mechanism through which grafted pumpkin rootstock plants acquire resistance to wax gourd wilt is still poorly understood. In this study, grafted wax gourd (GW) and self-grafted wax gourd (SW) were cultured at three concentrations [2.8 × 106 Colony Forming Units (CFU)·g-1, 8.0 × 105 CFU·g-1, and 4.0 × 105 CFU·g-1, expressed by H, M, and L]. Three culture times (6 dpi, 10 dpi, and 13 dpi) were used to observe the incidence of wilt disease in the wax gourd and the number of F. oxysporum spores in different parts of the soil and plants. Moreover, the physiological indices of the roots of plants at 5 dpi, 9 dpi, and 12 dpi in soil supplemented with M (8.0 × 105 CFU·g-1) were determined. No wilt symptoms in GW. Wilt symptoms in SW were exacerbated by the amount of FOB in the inoculated soil and culture time. At any culture time, the amount of FOB in the GW soil under the three treatments was greater than that in the roots. However, for the SW treatments, at 10 dpi and 13 dpi, the amount of FOB in the soil was lower than that in the roots. The total phenol (TP) and lignin (LIG) contents and polyphenol oxidase (PPO) and chitinase (CHI) activities were significantly increased in the GWM roots. The activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) initially decreased but then increased in the GWM roots. When the TP content decreased significantly, the LIG content and PAL and CHI activities increased initially but then decreased, whereas the PPO and POD activities did not change significantly in the SWM roots. The results indicated that the roots of the "Haizhan 1" pumpkin stock plants initiated a self-defense response after being infected with FOB, and the activities of PPO, POD, PAL, and CHI increased, and additional LIG and TP accumulated, which could effectively prevent FOB infection.

Morphological, molecular, and biological characterization of bulb rot pathogens in stored Lanzhou lily and the in vitro antifungal efficacy of three plant essential oils.

Lanzhou lily (Lilium davidii var. willmottiae) is an exclusive sweet lily variety indigenous to China, which is susceptible to bulbous rot caused by fungal infection during storage. This experiment tests the pathogenicity of the pure culture isolated from the diseased tissue was confirmed in accordance with Koch's postulates, and the pathomycetes were identified based on their morphological and molecular characteristics. Furthermore, the biological characteristics of the pathogens were investigated, followed by an evaluation of the antifungal effects of three plant essential oils against them. The results showed that two strains of fungi were isolated from Lanzhou lily rot, which were identified as Fusarium oxysporum Schl. and Aspergillus sydowii (Bain. Et sart.). In addition, the pathogenicity of these two strains of fungi was demonstrated that only F. oxysporum induced rot with similar symptoms during the post-harvest storage period. The biological characteristics of F. oxysporum indicated the potato maltose agar and lily dextrose agar were identified as the most suitable media. Sucrose was determined to be the optimal carbon source, while ammonium nitrate was found to be the best nitrogen source for the growth of F. oxysporum. Mycelial growth and sporulation of F. oxysporum occurred at an optimum pH value of 6. Total darkness facilitated mycelial growth and conidial germination. The ideal temperature for growth was found to be 28°C, while relative humidity did not significantly impact mycelial growth; however, a relative humidity of 55% was most favorable for spore production. Among the three essential oils tested, cinnamon essential oil displayed superior antifungal efficacy against F. oxysporum, whereas angelica essential oil and tea tree essential oil also exhibited moderate inhibitory effects against this pathogen. This research provides valuable theoretical insights for disease control during the storage and transportation of Lanzhou lily.

Cosmetic Stay-green Trait in Snap Bean and the Event Cascade That Reduces Seed Germination and Emergence

The persistent color (pc) trait in snap bean (Phaseolus vulgaris L.) is a member of the stay-green gene family and falls into the cosmetic subclass. Cosmetic stay-green variants remain green but lose photosynthetic competence during senescence. It is an economically useful trait in snap bean as a result of its effects on pod quality. The trait produces a dark-green, uniform appearance of fresh pods, but has other pleiotropic effects, including a light-green seed color, bleached-white cotyledons on emergence, and foliage and pods that remain green even while senescing. One additional pleiotropic effect is reduced field germination and emergence compared with white- and colored-seeded genotypes. Nevertheless, with the aid of seed-applied fungicides, pc types occupy ≈40% of commercial snap bean acreage in the United States. This research project was aimed at understanding why and how germination and emergence is affected in pc beans. The effect is thought to be related to soil-borne pathogens because fungicide treatment of pc seeds increases germination and emergence rates to levels comparable to treated white- and colored-seeded genotypes. For our experiments, we increased seeds of 45 experimental lines and commercial cultivars (25 of which were pc) under uniform growing conditions. Initial experiments documented that, in the laboratory, all seeds analyzed in a tetrazolium test had high viability. Furthermore, untreated seeds of pc and non-pc types germinated in the laboratory showed no difference in germinability, whereas in the field, germination of pc types was reduced significantly. In addition, pc types showed substantially greater infection rates of seeds and seedlings, with the main pathogen being Fusarium oxysporum Schl. f. sp. phaseoli Kendrick & Snyder. Water uptake by green pc seeds was significantly more rapid than white and colored seeds. Measurements of electrical conductivity revealed that pc types had greater solute leakage than other seed types. When seed anatomic structure was examined, pc types had a significantly thinner testa, especially the osteosclereid layer. The reduction in germination and emergence appears to begin with a thinner, more fragile testa showing increased cracking that may happen during seed harvest and conditioning (but certainly does happen during imbibition), allowing more rapid water uptake during germination that leads to testa rupture. Increased and rapid solute diffusion into the surrounding spermosphere stimulates and attracts pathogens to colonize the seeds before seedlings can become established. Seed handling and conditioning processes before planting could be modified to improve field emergence and stand establishment. Selection for thicker testa may also mitigate some of the damage observed during germination of pc cultivars.

Cloning and Expression of the Chitinase Encoded by ChiKJ406136 from Streptomyces Sampsonii (Millard & Burr) Waksman KJ40 and Its Antifungal Effect

The present study demonstrated that the chitinase gene ChiKJ406136 of Streptomyces sampsonii (Millard & Burr) Waksman KJ40 could be cloned using a PCR protocol and expressed in Escherichia coli (Migula) Castellani & Chalmers BL21 (DE3), and the recombinant protein had antifungal effect on four forest pathogens (Cylindrocladium scoparium Morgan, Cryphonectria parasitica (Murrill) Barr, Neofusicoccum parvum Crous, and Fusarium oxysporum Schl.) and also had the biological control effects on Eucalyptus robusta Smith leaf blight, Castanea mollissima BL. blight, Juglans regia L. blight and J. regia root rot. The results showed that ChiKJ406136 was efficiently expressed and a 48 kilodalton (kDa) recombinant protein was obtained. No significant change in protein production was observed in the presence of different concentrations of IPTG (isopropyl-b-D-thio-galactoside). The purified protein yield was greatest in the 150 mmol/L imidazole elution fraction, and the chitinase activities of the crude protein and purified protein solutions were 0.045 and 0.033 U/mL, respectively. The antifungal effects indicated that mycelial cells of the four fungi were disrupted, and the control effects of the chitinase on four forest diseases showed significant differences among the undiluted 10- and 20-fold dilutions and the control. The undiluted solution exhibited best effect. The results of this study provide a foundation for the use of S. sampsonii as a biocontrol agent and provides a new source for the chitinase gene, providing a theoretical basis for its application.

Efficient Synthesis and Bioactivity of Novel Triazole Derivatives.

Triazole pesticides are organic nitrogen-containing heterocyclic compounds, which contain 1,2,3-triazole ring. In order to develop potential glucosamine-6-phosphate synthase (GlmS) inhibitor fungicides, forty compounds of triazole derivatives were synthesized in an efficient way, thirty nine of them were new compounds. The structures of all the compounds were confirmed by high resolution mass spectrometer (HRMS), 1H-NMR and 13C-NMR. The fungicidal activities results based on means of mycelium growth rate method indicated that some of the compounds exhibited good fungicidal activities against P. CapasiciLeonian, Sclerotinia sclerotiorum (Lib.) de Bary, Pyricularia oryzae Cav. and Fusarium oxysporum Schl. F.sp. vasinfectum (Atk.) Snyd. & Hans. at the concentration of 50 µg/mL, especially the inhibitory rates of compounds 1-d and 1-f were over 80%. At the same time, the preliminary studies based on the Elson-Morgan method indicated that the compounds exhibited some inhibitory activity toward glucosamine-6-phosphate synthase (GlmS). These compounds will be further studied as potential antifungal lead compounds. The structure-activity relationships (SAR) were discussed in terms of the effects of the substituents on both the benzene and the sugar ring.

Screening and Identification of Cellulase-Producing Strain of Fusarium Oxysporum

Abstract Five strains were screened out from 120 strains of Fusarium Oxysporum Schl. isolated from different regions. Based on ITS analyses, the strains were determined as Fusarium Oxysporum Schl. The strain named as H57-1 produce the highest cellulase, which activity reach at 1.43 IU/mL. The most suitable reactive pH of the CMCase was 4.5∼5.5, and the most suitable reactive temperature is 60∼65°C. Its activity is stable at pH 5.3∼9.5 and 4∼50°C.

ISSR analysis of Fusarium oxysporum Schl. in Hebei province

Abstract An Orthogonal design is applied to the optimization of ISSR-PCR reaction system for Fusarium oxysporum Schl. The effect of the five main factors was tested. A most suitable ISSR-PCR reaction system for Fusarium oxysporum Schl. was established. The optimized reaction system consists of 20 ng template DNA, 1 U Taq DNA polymerase, 0.4 μmol/L primer, 0.2 mmol/L dNTPs, 4.0 mmol/L Mg2+ and 2.5 μL 10× buffer. Optimal annealing temperature was decided by different primers. 2 primers with stable amplification and rich polymorphism for ISSR were selected. Based on the optimizing, 30 isolated strains from Hebei were tested in order to analyse the genetic diversity between of Fusarium oxysporum Schl. The isolated 30 strains were clustered into 2 genetic line-ages at 0. 86 genetic similarity. The genetic lineages of 30 strains showed no obvious relation with their geographical originals.

First Report of Crown Rot of Grafted Cucumber Caused by Fusarium solani in China

Grafting has been widely and effectively used in cucumber (Cucumis sativus) cultivation for approximately 30 years in China to avoid Fusarium wilt caused by Fusarium oxysporum Schl. f. sp. cucumerinum Owen. In greenhouses, 90% of cucumbers are grafted onto pumpkin (Cucurbita moschata) rootstock. However, in March 2009, a severe crown rot causing yellowing and wilting of the leaves was observed on grafted cucumber in a large number of greenhouses in Lingyuan, western Liaoning Province in China. Symptoms consisted of dark brown, water-soaked lesions and a dense, white mycelial mat at the base of the stem. Lingyuan is the largest district for cucumber cultivation using grafting techniques in solar greenhouses in China. In 30 surveyed greenhouses in Sanshijiazi Village in the city of Lingyuan, the incidence of affected plants ranged from 10 to 40%, which caused serious economic losses. Fusarium spp. were isolated from the surface-sterilized basal stems of symptomatic plants on potato dextrose agar and incubated on potato sucrose agar for 4 days at 25°C. Colonies of the isolates produced a brown pigmentation and sparse, aerial mycelia, with a cream color on the underside. Conidiophores were elongated and branched or unbranched. Microconidia were abundant, hyaline, ellipsoid to ovoid, and 6 to 14 × 2.5 to 3.5 μm. Macroconidia were cylindrical, abundant, mostly two to six septate, 22 to 63 × 3.2 to 5.0 μm, with the apical cell rounded and blunt, and the basal cell rounded. On the basis of morphological characteristics, the fungus was identified as F. solani (C. Booth). For confirmation, the internal transcribed spacer region of rDNA was amplified and sequenced. A 449-bp sequence shared 99% homology with that of a F. solani GenBank accession previously reported from Japan (No. AF150473.1). The new sequence was deposited in GenBank (Accession No. HM015882). Pathogenicity of three isolates was determined in two experiments using different methods of inoculation. In one, 30 seedlings of pumpkin (C. moschata) with one true leaf each were inoculated by dipping their roots in a suspension of 106 spores ml-1, while control plants were mock inoculated with sterile water. Plants were then potted in a sterile mix of peat moss and vermiculite (2:1 vol/vol). In the other, pregerminated pumpkin seeds were sown in the same medium with a conidial suspension added at a rate of 106 spores ml-1, while other seeds were sown in sterile soil as controls. Plants for both experiments were maintained in a greenhouse at 25°C. Twelve days after inoculation, inoculated plants in both experiments showed a cortical rot on the crown and stem base with a brown, water-soaked appearance. Twenty-one days later, inoculated plants developed wilting and yellowed leaves. Disease incidence was 100%. No symptoms occurred on the control plants. Both experiments were repeated once with the same results. The pathogen was recovered from symptomatic tissue, confirming Koch's postulates. F. solani has been previously reported to cause root rot on cucurbit in California (2) and crown rot on grafted cucumber in the Netherlands (1). To our knowledge, this is the first report of crown rot of grafted cucumber caused by F. solani in China.

Pathogenicity and aggressiveness of Fusarium oxysporum Schl. in bottle gourd and bitter gourd

Fusarium oxysporum is responsible for a large range of diseases on economically important crops such as bitter gourd and bottle gourd. Pathogenicity and aggressiveness of F. oxysporum in bitter gourd and bottle gourd isolated from two breeding stations of East-West Company in the Philippines namely San Ildefonso, Bulacan and Lipa, Batangas were tested. Eleven F. oxysporum isolates from bitter gourd and 12 isolates from bottle gourd were inoculated on 7-day and 1-month-old bitter gourd and bottle gourd plants in the greenhouse. All F. oxysporum isolates from bitter gourd were pathogenic on 7-day-old and 1-month-old bitter gourd and nine out of 12 isolates from bottle gourd were pathogenic on bottle gourd. Three isolates from the infested soil were non-pathogenic on bottle gourd. There was a significant difference in aggressiveness of the isolates on their natural hosts (P ≤ 0.05). There also was a significant difference in the aggressiveness of isolates pathogenic on bitter gourd from Batangas and Bulacan (P ≤ 0.05) but isolates from Batangas and Bulacan had similar aggressiveness as bottle gourd (P ≥ 0.05). Aggressiveness of F. oxysporum on 7-day-old bitter gourd and bottle gourd was significantly different compared to those on 1-month-old plants, demonstrating an effect of the host age onaggressiveness. Correlations between aggressiveness of F. oxysporum isolates on 7-day-old and 1-month-old bitter gourd and bottle gourd were moderate (r = 0.63, 0.78). Out of 12 isolates from bottle gourd, only one isolate was pathogenic on 7-day-old bitter gourd. Four of the isolates from bitter gourd were pathogenic on 7-day-old bottle gourd but not on 1-month-old bottle gourd. No cross infection was observed on mature plants.

Phytotoxic effect of selected crude plant extracts on soil-borne fungi of common bean

Common bean (Phaseolus vulgaris L.) is an important food and cash crop particularly in Eastern, Southern and Great lake region. The efficacy of water based crude plant extracts of Neem (Azadirachta indica), Mexican marigold (Tagetes minuta), Tobacco (Nicotiana tobacum) and Peri-winkle (Vinca rosea) in controlling soil-borne fungi (Fusarium oxysporum Schl. f. sp. phaseoli) of common bean (Phaseolus vulgaris L.) was studied in the western province of Kenya. Thirty farms were used in the study carried out in August-September 2005 and March-June 2006. Broth microdilution method was used to determine minimum inhibitory concentration (MIC). All crude plant extracts controlled Fusarium yellows with varying efficacy. Neem extract was the most effective, while peri-winkle was the least. Wilt incidence was not affected by dosage regime. Neem is inhibitory to Fusarium growth at lower dosage than tobacco, Mexican marigold and peri-winkle with MIC ranging between 2.5 and 10.0 mg ml-1

Fungitoxic properties of four crude plant extacts on fusarium oxysporum schl. F. sp phaseoli.

Fusarium yellows is a disease of common beans (Phaseolus vulgaris, L.) caused by Fusarium oxysporum Schl. F. sp. phaseoli, it has been found to be important in Busia district of Western province, Kenya. The study on fungitoxic properties of four locally available crude plant extracts was aimed at evaluating their efficacy in controlling Fusarium yellows infestation under the field conditions. Crude plant extracts from Azadirachta indica, Tagetes minuta, Nicotiana tobacum and Vinca rosea were tested against Fusarium oxysporum Schl. F. sp. phaseoli. Participatory On-Farm Trials (POFT) in six (6) divisions were carried out in August-September 2005 and March- June 2006; a total of thirty (30) farms were randomly surveyed. Minimum Inhibitory Concentration (MIC) of crude plant extracts against Fusarium was determined by broth microdilution method. Analysis of variance (ANOVA) was performed on the data, using Genstat 8th edition statistical program (Release 8.11, Lawes Agricultural Trust, Rothamsted Experimental Station, Harpenden, UK). Means were separated using LSD. Crude plant extracts exhibited fungitoxic activity against Fusarium oxysporum Schl. F. sp. phaseoli, with varying degree of efficacy. Nicotiana tobacum and Vinca rosea were not effective, Azadirachta indica and Tagetes minuta exhibited significant control over Fusarium. Azadirachta indica performed better amongst all the plant extracts. Common bean treatment with Benomyl 1 significantly reduced (P≤0.05) wilt incidence and increased growth in comparison to negative (–ve) control. Azadirachta indica formulation gave a significant reduction in wilt incidence compared to the other three crude plant extracts formulations. It reduced the wilt incidence by 17.24% in comparison to Tagetes minuta, Nicotiana tobacum and Vinca rosea whose wilt incidence reduction ranged from 5.84-9.8%. Azadirachta indica inhibited Fusarium growth at lower dosage than Tagetes minuta, Nicotiana tobacum and Vinca rosea. Extracts from Azadirachta indica and Tagetes minuta are effective, cheap and ecofriendly promising methods for protecting common bean against Fusarium oxysporum Schl. F. sp. phaseoli.

Coordinated effects of root autotoxic substances and Fusarium oxysporum Schl. f. sp. fragariae on the growth and replant disease of strawberry

Effects of hydroxybenzoic acid, an important autotoxic substance in roots, on plant growth, photosynthesis and Fusarium oxysporum occurrence in succession cropping of strawberry were evaluated in this paper. It was found that plant growth was negatively regulated by hydroxybenzoic acid or inoculation with F. oxysporum. Compared with these single factor treatments, the combination of the hydroxybenzoic acid treatment and F. oxysporum inoculation caused more severe inhibition in plant growth, greatly enhanced the occurrence of disease symptoms, and significantly decreased the chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration. In the meantime, the chlorophyll fluorescence parameters in strawberry were also significantly affected. After the application of hydroxybenzoic acid, the original chlorophyll fluorescence rapidly increased, resulting in a combined corresponding decrease in the maximum chlorophyll fluorescence and the chlorophyll fluorescence transformation efficiency. The effects of hydroxybenzoic acid treatment on the above chlorophyll fluorescence parameters from inoculation were delayed. Similarly, the coordination of hydroxybenzoic acid and F. oxysporum showed an elevated negative effect on the degree of inhibition of leaf photosynthesis more than the single factor treatments.

Purification of Two Antimicrobial Substances Produced by Bacillus subtilis Strain B11 and Their Properties

Two antimicrobial substances produced by Bacillus subtilis strain B11 were purified by boiling, DEAE 52 anion exchange chromatography and aluminum oxide adsorption chromatography. These purified substances showed only one spot on silica gel thin layer chromatography (TLC). Antimicrobial assays showed that antimicrobial substances A and B inhibited the growth of plant pathogens such as Fusarium oxysporum Schl f.sp. niveum, Rhizoctonia solani, Ralstonia solanacearum and Xanthomonas oryzae pv. oryzae. In addition, antimicrobial substance B could also inhibit the growth of Magnaporthe grisea. These two antimicrobial substances were resistant to proteolytic enzymes and temperature as high as 121°C.

Synthesis and Fungicidal Activity of Novel 2-Oxocycloalkylsulfonylureas

A series of 2-oxocycloalkylsulfonylureas (2) have been synthesized in a six-step, three-pot reaction sequence from readily available cyclododecanone, cycloheptanone, and cyclohexanone. Their structures were confirmed by IR, 1H NMR, and elemental analysis. The bioassay indicated that some of them possess certain fungicidal activity against Gibberella zeae Petch. In general, compounds containing a 12-membered ring (2A) are more active than those containing a 6- or 7-membered ring (2B, 2C). In the series 2A, the compounds in which R is a disubstituted phenyl or pyrimidyl showed better activity than those in which R is a monosubstituted phenyl or pyrimidyl, and aryl-substituted compounds have somewhat higher activity than those substituted by pyrimidyl. The further bioassay showed that the representative of 2A, 2A15, has good fungicidal activities against not only G. zeae Petch but also Botrytis cinerea Pers, Colletotrichum orbiculare Arx, Pythium aphanidermatum Fitzp, Fusarium oxysporum Schl. f. sp. Vasinfectum, etc.

Insecticidal and Fungicidal Activities of Chitosan and Oligo-chitosan

The activity of chitosan and oligo-chitosan on several plant insects and pathogens were studied. Chitosan was active against lepidopterous and homopterous insects; the mortality was 80%. The insecticidal activity of chitosan to Plutella xylostella L. was higher than that to Spodoptera exigua Hübner. The mortality of six types of aphids was generally 60–80%, and the highest was 99.7%. Some fungicidal activity by oligo-chitosan was observed on 12 plant pathogens. The inhibition effect of oligo-chitosan to plant pathogens was improved with increasing oligomer concentration. The highest inhibition rate (80%) was against Phomopsis asparagi (sacc.a) Bubak (95%) and the inhibition rate against Fusarium oxysporum (Schl.) f. sp. Cucumernum owen, Rhizoctonia solani Kuhn and Fusarium oxysporum Schl. F. Sp. Uasinfectum (Atk.) Snyd. & Hans.

Reactions of field pea cultivars to four races of Fusarium oxysporum f. sp. pisi

Reactions of the 117 field pea cultivars available in Canada were evaluated to the four common races (1, 2, 5, and 6) of Fusarium oxysporum Schl. f. sp. pisi (van Hall) Sny. and Hans, the causal agent of fusarium wilt, in growth chambers. Based on the visual assessment of foliar wilt symptoms, 49 cultivars were resistant to at least one of the four races, and the remaining 68 cultivars were susceptible to all four races. Of these resistant cultivars, Ascona and 44 other cultivars were resistant to race 1; Impala to race 2; Aladin to races 1 and 2; and Radley and Princess to races 2, 5, and 6. In an effort to standardize the methodology for screening field pea for resistance to the pathogen, other quantitative parameters including shoot length, vascular discoloration, and shoot and root dry weights were evaluated on selected cultivars. Correlation analysis revealed that foliar wilt symptoms and the reduction in shoot length were highly correlated (r = -0.90, P < 0.01). The result suggests that the reduction in shoot length could be used to supplement the visual severity rating for fusarium wilt in field pea. Key words: Field pea, Pisum sativum, fusarium wilt, Fusarium oxysporum f. sp. pisi, resistance

Resistance to Fusarium Wilt Race 2 in the Pisum Core Collection

Plant breeders must be aware of sources of resistance to pathogens that affect their crops. Fusarium wilt caused by Fusarium oxysporum Schl. f. sp. pisi Snyd. & Hans. is a fungal disease that affects peas and is important worldwide. Resistance to the different races of the pathogen has been identified in adapted germplasm and from specific accessions in the United States World Collection of peas (Pisum sativum L.). The goal of this study was to evaluate the resistance to fusarium wilt race 2 in the Pisum core collection. Of the 452 accessions screened, 62 (14%) were resistant. The resistant accessions included accessions from P.s. ssp. elatius that were collected from 24 different countries. The wide distribution of resistance around the world precludes the identification of any single country or region as a source of resistance. Of the 62 accessions resistant to race 2, 39 are also resistant to race 1 based on data obtained from GRIN. One of the wild progenitors, PI 344012, possessed resistance to races 1 and 2.

Fusarium wilt of oil palm I. Possible causes of stunting

In West Africa the most serious disease of oil palm (Elaeis guineensis) is vascular wilt caused by Fusarium oxysporum Schl. f.sp. elaeidis. Although severe stunting of leaves has frequently been reported in this disease and has been assumed to be a result of disease induced water stress, this is the first investigation of the mechanisms and possible causes of this symptom. In diseased palms stunting was due to a large (up to 95%) decrease in the size of both the petiole and leaf lamina, which were almost entirely caused by a reduction in cell division, rather than cell size. When uninoculated plants were exposed to drought there was a reduction in leaf number but not leaf size. However, the application of an inhibitor of gibberellin synthesis (Paclobutrazol) to uninfected palms resulted in very similar symptoms which were also due to a reduction in cell division. The application of gibberellin to both infected and uninfected palms caused an increase in petiole length, by an increase in cell division, but had no effect of the size of leaf lamina. These results provide circumstantial evidence that stunting in diseased palms is not caused by water stress and, at least in part, is the result of changes in the level or activity of host gibberellin.

Induction Patterns of Chitinases in Yam Callus by Inoculation with Autoclaved Fusarium oxysporum, Ethylene, and Chitin and Chitosan Oligosaccharides

Chitinase involved in plant self-defense was investigated by inoculation of yam (Dioscorea opposita Thunb) callus with autoclaved mycelia of Fusarium oxysporum Schl. f. sp. raphani Kend. et Snyd., ethylene, and chitin and chitosan oligosaccharides. The induction of chitinase was followed by measuring the enzyme activity, and the isozyme pattern was also analyzed by activity staining and immunoblotting after disc- and SDS-PAGE. Autoclaved Fusarium oxysporum induced acidic chitinases named El and E3 with MW 33, 500 in the callus, while ethylene and oligosaccharides of chitin and chitosan induced some chitinases more basic than E1 and E3, in addition to E1 and E3. These included large chitinases with MW 38, 000 and immunologically different chitinases from E1 and E3. In total, nine chitinases were induced. Isozyme patterns of chitinase induced were different among the elicitors used, although E1 and E3 were commonly induced in all cases. Oligosaccharides of chitin and chitosan showed different chain-length d...