Control of chickpea wilt (Fusarium oxysporum f.sp. ciceris) using Trichoderma spp. in Ethiopia

Thirty-two Trichoderma isolates were collected from soils grown with chickpea in central highlands of Ethiopia. The eight isolates were identified by CAB-International as Trichoderma harzianum, T. koningii and T. pseudokoningii. In in vitro tests, all Trichoderma isolates showed significant (P < 0.05) differences in their colony growth and in inhibiting the colony growth of Fusarium oxysporum f.sp. ciceris, race 3. In potted experiment, four Trichoderma isolates were tested as seed treatment on three chickpea cultivars (JG-62 susceptible, Shasho moderately susceptible and JG-74 resistant) against F. oxysporum f.sp. ciceris, race 3. The result showed that T. harzianum and unidentified Trichoderma isolate T23 significantly reduced wilt severity and delayed disease onset. The degree of wilt severity and delay of disease onset varied with chickpea cultivars. Our study revealed that biological control agents such as Trichoderma can be a useful component of integrated chickpea Fusarium wilt management.     

Genetic Variability of Fusarium oxysporum f.sp. ciceris Population Affecting Chickpea in the Sudan

Fusarium wilt caused by Fusarium oxysporum f.sp. ciceris (Foc) is the most important soilborne disease of chickpea in the Sudan and many other countries. A total of 76 Foc isolates from six different chickpea‐growing states in the Sudan have been collected in this study to investigate the genetic diversity of Sudanese Foc isolates. Additional 14 Foc isolates from Syria and Lebanon were included in this study. All isolates were characterized using four random amplified polymorphic DNA (RAPD), three simple sequence repeats (SSR), five sequence‐characterized amplified region (SCAR) primers and three specific Foc genome primers. Based on the similarity coefficient, the results indicated two major clusters included seven subclusters. The isolates from the Sudan were grouped as identified as races 0, 2 and unknown races. The isolates from Syria and Lebanon were grouped together as they identified as races 1B/C and 6, respectively. This study identified a new race Foc (race 0) in the Sudan. The results of this study will be useful for breeders to design effective resistance breeding program in chickpea in the Sudan.     

Morphological and pathogenic variability of Indian isolates of Fusarium oxysporum f. sp. ciceris causing chickpea wilt

Wilt of chickpea (Cicer arietinum) caused by Fusarium oxysporum f. sp. ciceris is prevalent in almost all chickpea growing areas of the world and its incidence varied from 14.1 to 32.0% in the different states of India surveyed. The isolates were highly variable in their colony growth pattern, size of colony and pigmentations. The size of microconidia varied from 5.1–12.8 × 2.5–5.0 μm, whereas macroconidia ranged from 16.5–37.9 × 4.0–5.9 μm with 1–5 septations. One hundred and twelve isolates were grouped into 12 categories on the basis of their radial growth, size of macroconidia and growth pattern. Majority of the isolates were highly pathogenic causing more than 50% wilt in chickpea cultivar JG 62. Virulence analysis of 56 representative isolates on a set of 18 cultivars of chickpea, including 10 international differentials, grouped them into three categories. Chickpea cultivar KWR 108 differentiated all isolates of Punjab, Haryana and Delhi states and a few isolates of Rajasthan from others by showing resistant reactions and were placed in the first group. The rest of the isolates of Rajasthan state showed susceptible reactions on KWR 108 placed in a second group. Cultivar CPS 1 distinguished the isolates of Jharkhand state and placed them into a third group. An international set of cultivars recommended for race differentiation were not able to distinguish all the isolates into known races of the pathogen, therefore cultivar KWR 108 should be included in the existing differential set of cultivars.     

Biological control of Fusarium oxysporum f. sp. radicis-cucumerinum by some Trichoderma harzianum isolates

The purpose of this study was to investigate the effects of isolates T₂₂, T₉ and T₆ of Trichoderma harzianum on isolate F₄₂ of Fusarium oxysporum f. sp. radicis-cucumerinum. The effect of T. harzianum isolates on controlling disease was examined under greenhouse conditions. Results showed that these three isolates, respectively, had the high effect on inhibition of pathogen growth. In examining the severity of disease in the greenhouse, it was found that isolate T₂₂ had the greatest effect on controlling the pathogen. The results of volatile compounds showed that these isolates, respectively, were effective in reducing mycelial growth of isolate F₄₂. The highest peroxidase activity was observed on the fourth day in isolate T₆ and the highest phenylalanine ammonia lyase enzyme activity was observed on the fifth day in isolate T₂₂. Based on the results, isolate of T₂₂ showed the greatest effect on the induction of resistance against F₄₂ and may be a successful agent for biological control of root and stem rot of cucumber.     

Studies on the population dynamics and integrated management of Fusarium oxysporum f. sp. psidi (Fop), a cause of guava (Psidium guajava) wilt

To assess the impact of non-host crops intercropping, bioagents and oil cakes, on population dynamics of Fusarium oxysporum f. sp. psidii (Fop) and wilt of guava. Lowest population of Fop was recorded in garlic followed by intercropping with marigold with reduction of 84.9 and 83.9%, respectively. Bioagents viz; Aspergillus niger, Trichoderma viride and Trichoderma harzianum reduced the Fop population significantly, with the lowest in T. harzianum followed by A. niger. Garlic bulb extract exhibited maximum inhibition of Fop growth (2.7 cm) followed by marigold (2.4 cm), respectively, over control. Neem cake significantly reduced population of Fop, closely followed by mahua cake, over control. Integration of neem cake + T. harzianum + garlic reduced the Fop population significantly, over control, followed by neem cake + T. harzianum + marigold but neem cake + T. harzianum + marigold reduced wilt disease significantly in comparison to neem cake + T. harzianum + garlic inter-cropping.     

First record of Fusarium vascular wilt on grapevine in Egypt

During the summer season of 2003 and 2004, wilt syndromes of grapevine leaves (Cv. crimson) and vascular discolouration of roots have been observed in 2-year-old grapevine plants in the field at two sides in Gharbeia Governorate, Egypt. First, symptoms of wilt began on bottom leaves borderline as chlorosis and then these turned to necrotic spots and the leaves died. Wilt symptoms were spread to apical associated with vascular discolouration of roots and stem basal. Routine isolations of discoloured root tissue from diseased plant yielded eight isolates of Fusarium oxysporum Schlechtend only where no other fungi were developed. Microscopic examination revealed the presence of three shapes of microconidia, first is avoid shape non-septate measuring 2.5–3.0 μm × 6–10 μm, second is cylindrical with one septa measuring 2.6 μm × 17.0 μm and third shape also cylindrical with two septate measuring 3.0 μm × 20.0 μm. Macroconidia was rarely with three septate measuring 3.5– 4.0 μm × 35.0–38.0 μm, and chlamydospores were found singly or in pairs or chains. F. oxysporum isolates attacked grapevine plants (Cv. crimson) causing vascular wilt (66.7%) and root-rot syndrome (33.3%). In vitro isolates of F. oxysporum causing wilt of grapevine (Cv. crimson) varied for producing lytic enzymes, i.e. polygalacturonase (PG) and cellulase. The reactions of several grapevines (Cvs.) with a virulent isolate of F. oxysporum indicated the presence of two different symptoms, i.e. vascular wilt only on grapevine plants (Cv. crimson) and root-rot on the other grapevine (Cvs.), i.e. superior, Thompson, King robi and flame seedless. All F. oxysporum isolates caused vascular wilt of grapevine Cv. crimson, successfully reisolated from symptomatic vascular infected tissue and complete identification on the basis of colony, conidia morphology and host range at formae speciales level as F. oxysporum f. sp. herbemontis (Tochetto) Gordan. This is the first report of Fusarium wilt on grapevine in Egypt.     

First Record of Fusarium Wilt of Tobacco in Greece Imported as Seedborne Inoculum

Leaf yellowing and brown discoloration was observed in tobacco plants cv. Burley TN97 in tobacco fields of central Greece in 2002. Fusarium oxysporum f. sp. nicotianae was isolated from symptomatic plants and Koch's postulates were fulfilled. The pathogenicity of the isolated fungus was examined on five tobacco cultivars (Burley TN97, BurleyB21, VirginiaBE9, Virginia Niki and Anatolika KE26/2). The pathogen was present in tobacco seed batches imported in 2000 and 2001, which indicates that the infected seed is most probably the primary source of the disease in Greece. As Fusarium oxysporum f. sp. vasinfectum can also cause vascular wilt in tobacco, the hypothesis that the isolated F. oxysporum strain belongs to f. sp. vasinfectum was excluded by a pathogenicity test to cotton cv. Acala SJ‐2. This is the first report of F. oxysporum f. sp. nicotianae in Greece and the second in the European Union, although the seedborne nature of the pathogen has not been previously reported in Europe.     

Induction of systemic resistance in chickpea against Fusarium wilt by Bacillus strains

Plant growth promoting rhizobacteria (PGPR) strains Rb29 (B. amyloliquefaciens MF352007), Bs1 (B. subtilis MF352017) and Bt1 (B. tequilensis MF352019) were tested for growth promotion and for their ability to induce systemic resistance against Fusarium wilt, a vascular disease of chickpea, using two methods that include whole plant and a split-root system. Bacillus strains and Fusarium oxysporum f. sp. ciceris (FOC) were inoculated on separate halves of roots of chickpea seedlings at the same time and then planted in separate pots either in superposition or one side of the other. All Bacillus strains systemically induced resistance against FOC, and significantly (p < 0.05) reduced the wilt disease by 98–100%. Application of Bacillus strains effectively enhanced plant growth, leading to increased plant height, root length, a fresh and dry weight of shoots and roots. These results help to explain the role of strains of Bacillus in growth promotion and biological control of Fusarium wilt in chickpea. This is the first report of systemic-induced resistance against Fusarium wilt in chickpea obtained by application of Bacillus strains to a root system spatially separated from the FOC-inoculated root.     

Anatomical and biochemical aspects of interaction between roots of chickpea and Fusarium oxysporum f. sp. ciceris race 2

Roots of the susceptible “JG-62” and resistant “WR-315” chickpeas (Cicer arietinum L.) were inoculated with a conidial suspension of Fusarium oxysporum f. sp. ciceris. Anatomical and biochemical studies were carried out in a time-course manner to elucidate the infection process and plant defence reactions. Scanning electron microscope images revealed fungal colonisation in the root hair region. Early occurrence of fungal biofilms associated with the infected “JG-62” root epidermis was also visualised. After 96 h of inoculation, a gradual accumulation of polysaccharide positive deposits was observed in the xylem vessels of the infected “JG-62” roots. Fungal mycelium was observed in the vessel lumen of infected “JG-62” after 22 days of inoculation. Due to fungal invasion during this period, some of the vessels also appeared collapsed in “JG-62”, whereas vessels in “WR-315” remained intact. The host plant defence responses specifically linked to the susceptible interactions were the induction of ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase in roots and shoots.     

Genetic Variation of Strawberry Fusarium Wilt Pathogen Population in Korea

Strawberries are a popular economic crop, and one of the major plantations and exporting countries is Korea in the world. The Fusarium oxysporum species complex (FOSC) is a soil-borne pathogen with genetic diversity, resulting in wilt disease in various crops. In Korea, strawberries wilt disease was first reported in the 1980s due to the infection of FOSC, causing significant economic damage every year. The causal agent, F. oxysporum f. sp. fragariae, is a soil-borne pathogen with a characteristic of FOSC that is difficult to control chemically and mutates easily. This study obtained genetic polymorphism information that was based on AFLP, of F. oxysporum f. sp. fragariae 91 strains, which were isolated from strawberry cultivation sites in Gyeongsangnam-do and Chungcheongnam-do, and compared strains information, which was the isolated location, host variety, response to chemical fungicide, and antagonistic bacteria, and mycelium phenotype. As a result, AFLP phylogeny found that two groups were mainly present, and group B was present at a high frequency in Gyeongsangnam-do. Group B proved less sensitive to tebuconazole than group A through Student’s t-test. In addition, the fractions pattern of AFLP was calculated by comparing the strain information using PCA and PERMANOVA, and the main criteria were separated localization and strawberry varieties (PERMANOVA; p < 0.05). And tebuconazole was different with weak confidence (PERMANOVA; p < 0.10). This study suggests that the F. oxysporum f. sp. fragariae should be continuously monitored and managed, including group B, which is less chemically effective.     

Race Profiling and Molecular Diversity Analysis of Fusarium oxysporum f.sp. ciceris Causing Wilt in Chickpea

Seventy isolates of Fusarium oxysporum f.sp. ciceris (Foc) causing chickpea wilt representing 13 states and four crop cultivation zones of India were analysed for their virulence and genetic diversity. The isolates of the pathogen showed high variability in causing wilt incidence on a new set of differential cultivars of chickpea, namely C104, JG74, CPS1, BG212, WR315, KWR108, GPF2, DCP92‐3, Chaffa and JG62. New differential cultivars for each race were identified, and based on differential responses, the isolates were characterized into eight races of the pathogen. The same set of isolates was used for molecular characterization with four different molecular markers, namely random amplified polymorphic DNA, universal rice primers, simple sequence repeats and intersimple sequence repeats. All the four sets of markers gave 100% polymorphism. Unweighted paired group method with arithmetic average analysis grouped the isolates into eight categories at genetic similarities ranging from 37 to 40%. The molecular groups partially corresponded to the states of origin/chickpea‐growing region of the isolates as well as races of the pathogen characterized in this study. The majority of southern, northern and central Indian populations representing specific races of the pathogen were grouped separately into distinct clusters along with some other isolates, indicating the existence of variability in population predominated by a single race of the pathogen. The present race profiling for the Indian population of the pathogen and its distribution pattern is entirely new. The knowledge generated in this study could be utilized in resistance breeding programme. The existence of more than one race, predominated by a single one, in a chickpea cultivation zone as supported by the present molecular findings is also a new information.     

Influence of Meloidogyne incognita on Fusarium Wilt of Tomato at or below the Minimum Temperature for Wilt Development

''Bonny Best'' tomato plants were grown at 16, 21, or 24 C for 28 d in soil infested with either of two isolates of Fusarium oxysporum f. sp. lycopersici race 1 and Meloidogyne incognita. Significant levels of fusarium wilt occurred at all temperatures including 16 C, which has not been reported previously. One Fusarium isolate resulted in the highest levels of disease incidence at 21 and 24 C in the presence of root-knot nematodes, and at 24 C when the nematodes were not present. At 16 C there was no significant difference in the number of plants infected by the second Fusarium isolate alone or in combination with root knot nematodes, although the presence of nematodes resulted in a significant increase in the percentage of disease occurrence and vessel infection at 21 C.     

Analysis of Vegetative Compatibility Groups of Fusarium oxysporum from Eruca vesicaria and Diplotaxis tenuifolia

From 2002 to 2004, wilted plants of different species of rocket (Eruca vesicaria and Diplotaxis spp.) were found for the first time in Europe, in greenhouse cultivations in Piedmont and Lombardy, northern Italy. The causal agent of the disease was found to be Fusarium oxysporum. Vegetative compatibility analysis was carried out on 46 isolates of the fungus, 41 of them obtained from wilted rocket (E. vesicaria and D. tenuifolia) and five reference strains, in order to increase the knowledge on the causal agent of recent epidemics of Fusarium wilt on rocket in Italy. The analysis showed the presence of two vegetative compatibility groups (VCGs) (VCG 0101 and VCG 0220) pathogenic on both kinds of rocket. The two VCG populations, which were classified as formae specialesconglutinans and raphani, respectively, are spread in the area of epidemics but are not related to the host species from which they were isolated (D. tenuifolia or E. vesicaria). This finding shows the heterogeneity of the causal agent of Fusarium wilt on rocket in Italy.     

Status of chickpea fusarium wilt (Fusarium oxysporum f.sp. ciceris) in northwestern Ethiopia

Surveys for incidence of fusarium wilt of chickpea were carried out in six districts of North and South Gondar, and East Gojam administrative zones, Amhara National Regional State in northwestern Ethiopia in 2006–2007 and 2007–2008 main cropping seasons. In each district, five representative peasant administrations (PAs) were selected based mainly on chickpea-growing area coverage, and, in each PA, disease was assessed in five randomly selected farmers’ fields. In the two cropping seasons, the mean incidences recorded in each district were as follows: Gondar Zuria, 34.16% and 34.11%; Dembia, 37.90% and 35.36%; Libo-Kemkem, 34.74% and 28.81%; Fogera, 34.74% and 28.81%; Dejen, 34.74% and 28.81% and Enemay, 33.34% and 37.64%. The result indicated that fusarium wilt is currently highly distributed in all surveyed chickpea-growing areas of northwestern part of Ethiopia. Therefore, possible management options are vital to alleviate the problem.     

Biological Control of Fusarium Wilt in Tomato Caused by Fusarium oxysporum f. sp. lycopersici by AMF Glomus intraradices and some Rhizobacteria

In the present study, the effects of the arbuscular mycorrhizal fungus (AMF) Glomus intraradices Schenck & Smith and four rhizobacteria (RB; 58/1 and D/2: Pseudomonas fluorescens biovar II; 17: P. putida; 21: Enterobacter cloacae), which are the important members of the rhizosphere microflora and biological control agents against plant diseases, were examined in the pathosystem of Fusarium oxysporum f. sp. lycopersici [(Sacc) Syd. et Hans] (FOL) and tomato with respect to morphological parameters (fresh and dry root weight) and phosphorous (P) concentration in the roots. Treatments with single and dual inoculation with G. intraradices and RB strains reduced disease severity by 8.6–58.6%. Individual bacteria inoculations were more effective than both the single AMF and dual (G. intraradices + RB) inoculations. In addition, the RB and G. intraradices enhanced dry root weight effectively. Significant increases in root weights were recorded particularly in the triple inoculations compared with single or dual inoculations. Compared with the non‐treated controls all biological control agents increased P‐content of treated roots of plants. Colonization with RB increased especially in triple (FOL + G. intraradices + RB) inoculations whereas colonization of G. intraradices was significantly decreased in treatment of FOL + G. intraradices compared with triple inoculations. The results suggest that suitable combinations of these biocontrol agents may ameliorate plant growth and health.     

Effect of Simulated Soil Solarization and Organic Amendments on Fusarium Wilt of Rocket and Basil Under Controlled Conditions

Pot trials were carried out under controlled conditions to evaluate the effectiveness against Fusarium wilt of rocket (Fusarium oxysporum f.sp. conglutinans) and basil (F. oxysporum f.sp. basilici) of soil amendments based on a patented formulation of Brassica carinata defatted seed meal and compost, combined or not with a simulation of soil solarization. The soil solarization treatment was carried out in a growth chamber by heating the soil for 7 and 14 days at optimal (55–52°C for 6 h, 50–48°C for 8 h and 47–45°C for 10 h/day) and sub‐optimal (50–48°C for 6 h, 45–43°C for 8 h and 40–38°C for 10 h/day) temperatures similar to those observed in summer in solarized soil in greenhouses in Northern Italy. Two subsequent cycles of plant cultivation were carried out in the same soil. Even at sub‐optimal temperature regimes, 7 days of thermal treatment provided very valuable results in terms of disease control on both rocket and basil. In general, the thermal treatment was more effective against F. oxysporum f.sp. basilici than against F. oxysporum f.sp. conglutinans. Control of Fusarium wilt of rocket is improved with 14 days of thermal treatment. The combination of organic amendments with a short period of soil solarization (7 or 14 days), although not providing any improvement to the level of disease management, did significantly increase biomass and positively affected yield.     

Common Bean Reaction to Fusarium oxysporum f. sp. Phaseoli, the Cause of Severe Vascular Wilt in Central Africa

During the September‐December season of 1990, severe symptoms of Fusarium wilt were for the first time observed on a popular climbing bean (Phaseolus vulgaris L.) cultivar. G 2333. introduced within the previous 5 years. Seventy‐three bean genotypes were screened for resistance lo the disease, using artificial inoculation. The effect of inoculation density on the reaction of four selected genotypes was also investigated. Of the 29 climbing bean genotypes evaluated, 19 were resistant, including 11 of the 15 pre‐release or released cultivars. Of the 44 bush bean cultivars evaluated, 28 were resistant, five were intermediate and 11 were susceptible. All susceptible cultivars showed vascular discoloration. In both susceptible and resistant genotypes, the fungus spread almost equally from the entry points in inoculated roots to the base of the plants, but colonization and vertical spread within the vascular system were markedly less in resistant than in susceptible cultivars. At 20 and 30 cm above soil level, the fungus was only recovered from susceptible cultivars. Increasing inoculum density from 10² to 10⁷ conidia/ml did not affect the resistance of cultivars RWR 950 and G 685 but. in the susceptible cultivars G 2333 and MLB‐48‐89 A. it resulted in early appearance, high incidence and severity of the disease.     

Influence of Plant Root Exudates, Germ Tube Orientation and Passive Conidia Transport on Biological Control of Fusarium Wilt by Strains of Nonpathogenic Fusarium oxysporum

In earlier studies, biological control of Fusarium wilt of cucumber induced by Fusarium oxysporum f. sp. cucumerinum was demonstrated using nonpathogenic strains C5 and C14 of Fusarium oxysporum. Strain C14 induced resistance and competed for infection sites whether roots were wounded or intact, whereas strain C5 required wounds to achieve biocontrol. In the current work, additional attributes involved in enhanced resistance by nonpathogenic biocontrol agents strains to Fusarium wilt of cucumber and pea were further investigated. In pre-penetration assays, pathogenic formae specials exhibited a significantly higher percentage of spore germination in 4-day-old root exudates of cucumber and pea than nonpathogens. Also, strain C5 exhibited the lowest significant reduction in spore germination in contrast to strain C14 or control. One-day-old cucumber roots injected with strain C14 resulted in significant reduction in germ tube orientation towards the root surface, 48–96 h after inoculation with F. o. cucumerinum spores, whereas strain C5 induced significantly lower spore orientation of the pathogen and only at 72 and 96 h after inoculation. In post-penetration tests, passive transport of microconidia of pathogenic and nonpathogens in stems from base to apex were examined when severed plant roots were immersed in spore suspension. In repeated trials, strain C5, F. o. cucumerinum and F. o. pisi were consistently isolated from stem tissues of both cucumber and pea at increasing heights over a 17 days incubation period. Strain C14 however, was recovered at a maximum translocation distance of 4.6 cm at day 6 and later height of isolation significantly declined thereafter to 1.2 cm at day 17. In pea stem, the decline was even less. Significant induction of resistance to challenge inoculation by the pathogen in cucumber occurred 72 and 96 h after pre-inoculation with biocontrol agents. Nonetheless, strain C14 induced protection as early as 48 h and the maximum resistance was reached at 96 h. The presented data confirm the previous findings that attributes important for nonpathogenic fusaria to induce resistant are: rapid spore germination and orientation in response to root exudate; active root penetration and passive conidia transport in stem to initiate defence reaction without pathogenicity and enough lag period between induction and challenge inoculation. Strain C14 possesses all these qualifications and hence its ability to enhance host resistance is superior than strain C5.     

Effect of combination of bio-agents and mineral nutrients for the management of alfalfa wilt pathogen Fusarium oxysporum f. sp. medicaginis

Abstract

Biological and nutrient management of soil borne disease is increasingly gaining stature as a possible practical and safe approach. Inhibitory effects of fungal and bacterial antagonists were tested under in vitro conditions against the wilt pathogen of alfalfa Fusarium oxysporum f. sp. medicaginis. Trichoderma harzianum and Pseudomonas fluorescens (PI 5) were found to be effective against the alfalfa wilt pathogen. Manganese sulphate at 500 and 750 ppm inhibited the mycelial growth of F. oxysporumf. sp. medicaginis under in vitro conditions. In pot culture studies, manganese sulphate at 12.5 mg/kg reduced the wilt incidence (23.33%). Combined application of manganese sulphate 12.5 mg/kg + T. harzianum 1.25 mg/kg of soil significantly reduced the wilt incidence accompanied by improved plant growth and yield in pot culture. The mixture of manganese sulphate (25 kg/ha) + T. harzianum (2.5 kg/ha) significantly reduced the wilt incidence when applied as a basal dose in the field conditions. The average mean of disease reduction was 62.42% over control.     

棉花枯萎、黄萎病拮抗芽孢杆菌的抗菌蛋白特性

从土贝母和腊肠等中药和发酵食品中筛选出对棉花枯萎、黄萎病菌有广谱拮抗作用的芽孢杆菌29株,其中有12株菌产抗菌蛋白。有5株抑菌活性较强:H110、H184、H216、B316和B382。经初步鉴定,H110和H184为枯草芽孢杆菌,H216、B316和B382为地衣芽孢杆菌。5株菌的蛋白粗提液对热稳定,对蛋白酶K、胰蛋白酶均不敏感,但H184、H216的蛋白粗提液对胃蛋白酶部分敏感。