Association of induction of protease and chitinase in chickpea roots with resistance to Fusarium oxysporum f.sp. ciceri

To improve the breeding of chickpea varieties with resistance to Fusarium wilt, an attempt was made to analyse the biochemical basis of disease resistance by measuring levels of chitinase, β-1,3-glucanase, protease and proteinase inhibitor activities in dry and soaked seeds and in root and shoot tissues of wilt-resistant and wilt-susceptible cultivars. Marginal variation was observed in the levels of the candidate proteins in dry or soaked seeds. Chitinase activity was higher in roots than in shoots or cotyledons. No proteinase inhibitor activity was detected in root and shoot tissue of any of the cultivars. When the levels of these proteins were analysed in resistant (Vijay) and susceptible (JG-62) cultivars during development of wilt by growing plants in soil infested with F. oxysporum f.sp. ciceri , race 1, both cultivars showed induction of chitinase activity in the roots. However, the induced activity in JG-62 (3.82 U g⁻¹) was equivalent to the constitutive level in Vijay (3.90 U g⁻¹) and much lower than that induced in Vijay (5.18 U g⁻¹). Induction of protease activity was observed only in root extracts of Vijay when challenged by the pathogen. The root extract of Vijay showed in vitro antifungal activity in a plate assay. Simultaneous induction of proteolytic and chitinolytic activities specifically in the resistant cultivar was correlated with antifungal properties of root extracts effective in conferring resistance.     

Root exudates associated with the resistance of four chickpea cultivars (Cicer arietinum) to two races of Fusarium oxysporum f.sp. ciceri

The germination of race 1 spores of Fusarium oxysporum f. sp. ciceri was significantly inhibited by the root exudate of the wilt-resistant chickpea cvs CPS1 and WR315 compared to untreated spores and spores treated with root exudates from susceptible cultivars. The effect was concentration dependent, such that the exudate from 1 g of root in 2 ml of water almost completely inhibited spore germination, whereas the exudate from 1 g of root in 20 ml water did not do so. The inhibitory effects of the active exudates were negated when the apolar components of the exudates were removed by extraction with ethyl acetate. The root exudates of the susceptible cv. JG62 and the late wilting cv. H208 did not inhibit germination. The hyphal growth of germinated spores was also strongly inhibited by the concentrated exudates of CPS1 and WR315, and diluted exudates were less potent. The highest concentration of the exudate of the susceptible cv. JG62 showed some inhibition of hyphal growth, whereas none of the exudates of H208 were found to contain any antifungal activity. The effect of the exudates on the spores of race 2 was similar to that reported for race 1, except that the water-soluble components of the crude root exudate of WR315 after ethyl acetate extraction were also found to inhibit germination significantly. Overall, the spores of race 2 appeared to be more susceptible to the effects of the exudates. The ethyl acetate fractions of the root exudates of CPS1 and WR315 strongly inhibited germination and hyphal growth of both race 1 and race 2, the effect being concentration dependent. The results suggest that the resistance of chickpeas to vascular wilt depends, at least in part, upon the antifungal activity of the root exudates. Differences in the expression of resistance in the field could depend upon the concentration or rate of production of constitutive antifungal components by the root.     

Pathogenicity of Fusarium solani f.sp. cucurbitae race 1 to courgette

Fusarium solani f. sp.cucurbitae race 1 causes foot rot in courgette (Cucurbita pepo). The pathogen could be distinguished fromFusarium solani from sweet pepper (Capsicum annuum) both morphologically and in its host range.In inoculation experiments all nine cultivars of the six species of Cucurbitaceae tested were susceptible. Courgette Green became diseased after inoculation with a spore suspension by root dipping or adding the suspension to the soil around the stem base or spraying the whole plant with it.Both wounded and young plants died more quickly than unwounded and older plants. With low inoculum densities the plants were affected more slowly than with high densities and the differences in susceptibility of the Cucurbitaceae tested were more pronounced.From infected courgette seeds the fungus could be reisolated until 6 months after harvest.This is the first record of this pathogen in courgettes in the Netherlands.Samenvatting Fusarium solani f. sp. cucurbitae fysio 1 is de oorzaak van een voetrot in courgette. Het pathogeen is morfologisch en door middel van een waardplantenreeks goed vanF. solani uit paprika te onderscheiden.In inoculatieproeven waren de getoetste Cucurbitaceae in meer of mindere mate gevoelig voorF. solani f. sp.cucurbitae. Bij courgette Green werden zowel gedompelde, als aangegoten, als bespoten planten door het pathogeen aangetast. Zowel verwonde als niet-verwonde planten werden aangetast als ook planten van verschillende leeftijden. Niet-verwonde en ook oudere planten stierven minder snel af dan verwonde en jongere planten. Bij lagere inoculumdichtheden werden de planten minder snel aangetast dan bij hogere dichtheden en waren de verschillen in vatbaarheid voor het pathogeen tussen de getoetste Cucurbitaceae duidelijker.Uit courgette zaad, dat met het pathogeen was besmet, kon de schimmel tot 6 maanden na zaadwinning opnieuw worden geïsoleerd.Dit is de eerste melding van dit pathogeen in courgette in Nederland.     

A new race of Fusarium oxysporum f. sp. lactucae of lettuce

Fusarium oxysporum f. sp. lactucae, the causal agent of fusarium wilt of lettuce (Lactuca sativa), occurs in most countries in which lettuce is grown and causes serious economic losses. Three races (1, 2 and 3) of the pathogen have previously been identified on the basis of their ability to cause disease on differential lettuce cultivars, as well as by means of molecular tools developed to characterize different races of this pathogen. Only race 1 has been detected in Europe so far. In this study, two isolates of F. oxysporum, obtained from lettuce plants grown in the Netherlands showing symptoms of wilt, have been characterized by combining the study of pathogenicity with differential cultivars of lettuce and molecular assays to determine whether the isolates are different from the known races of F. oxysporum f. sp. lactucae. This study reports the presence of F. oxysporum f. sp. lactucae for the first time in the Netherlands. The causal pathogen has been identified, using the IRAP‐SCAR technique, as a new race of F. oxysporum f. sp. lactucae. Specific primers have been designed to identify this new race.     

香蕉枯萎病菌1号和4号生理小种细胞壁降解酶的比较

对香蕉枯萎病菌1号和4号生理小种的细胞壁降解酶进行比较。通过测定4号生理小种在寄主体内细胞壁降解酶的活性发现,能检测到多聚半乳糖醛酸酶(PG)、果胶甲基半乳糖醛酸酶(PMG)、多聚半乳糖醛酸反式消除酶(PGTE)、果胶甲基反式消除酶(PMTE)和纤维素酶(Cx)的活性。在不同碳源培养条件下,2个生理小种均有以上5种酶的活性,以1%柑桔果胶为碳源时产生的PMG和PG活性明显高于其他几种酶的活性,而以1%CMC为碳源时,所产生的Cx都比其他几种酶的活性高。细胞壁降解酶同工酶电泳后发现,4号生理小种在寄主体内和体外培养时都比1号生理小种多分泌一种PG。2个生理小种在体外培养时分泌的PMG、PGTE和PMTE没有差异。4号生理小种在寄主体内比1号生理小种多分泌一种PMG,却少分泌一种PGTE,2个生理小种在寄主体内的PMTE则没有差异。     

根癌农杆菌介导的香蕉枯萎病菌4号生理小种的转化

 本文针对香蕉枯萎病菌4号生理小种这一对我国香蕉生产构成了极大威胁的检疫性有害生物,建立了根癌农杆菌介导的该生理小种的转化体系,确定了影响转化效率主要因子的最佳条件分别是:共培养乙酰丁香酮(AS)浓度为200μmol/L、共培养时间为48 h、培养温度为25℃、诱导培养基pH值为5.5。此条件下,转化效率达到21~24个转化子/10⁴香蕉枯萎病菌孢子。PCR和Southern杂交分析表明外源的T-DNA已经成功随机地整合到该病原菌基因组中,且多为单拷贝。应用该转化体系已获得近25 000个转化子,为研究该生理小种致病机制奠定了基础。     

Resistance sources to Fusarium oxysporum f. sp. cubense tropical race 4 in banana wild relatives

Target trait evaluation in crop wild relatives is an important prerequisite for efficiently using the potential useful genes located in this valuable germplasm. Over recent decades, Fusarium oxysporum f. sp. cubense tropical race 4 (Foc‐TR4) has seriously threatened worldwide banana plantations. Breeding new resistant cultivars from wild banana species is expected to provide invaluable additional resources. However, knowledge on resistance to Foc‐TR4 in wild Musa species is very limited. In this study, eight genotypes of wild banana relatives (Musa acuminata subsp. burmannica, M. balbisiana, M. basjoo, M. itinerans, M. nagensium, M. ruiliensis, M. velutina and M. yunnanensis) were characterized for resistance to Foc‐TR4 in both greenhouse and field conditions. Most wild bananas showed higher resistance levels to Foc‐TR4 than the reference cultivars ‘Brazilian’ (AAA, susceptible) and ‘Goldfinger’ (AAAB, moderate resistance). Among the wild species, M. balbisiana showed the highest levels of disease intensity followed by M. acuminata subsp. burmannica. Some individuals of M. yunnanensis, M. nagensium, M. ruiliensis and M. velutina showed low levels of rhizome discolouration in greenhouse conditions, but were resistant in the field. No symptoms were observed on M. basjoo and M. itinerans, suggesting higher levels of resistance to Foc‐TR4. The results revealed different sources of resistance to Foc‐TR4 in banana wild relatives, which constitute a valuable genetic resource for banana breeding programmes aiming to produce cultivars resistant to fusarium wilt.     

Selection methods for determining resistance of carnation cultivars to Fusarium oxysporum f.sp. dianthi

The level of resistance of carnation ( Dianthus caryophyllus ) cultivars to wilt caused by Fusarium oxysporum f.sp. dianthi was compared in root-dip-inoculated plants grown in pots (filled with tuff or sandy soil) in a greenhouse and plants grown in a field where the soil was artificially infested with the fungus. In the field, wilt symptoms appeared first in susceptible and subsequently in resistant cultivars; none was immune. Variations in the level of resistance were expressed either by different percentages of wilted plants (i.e. disease incidence) or by delayed disease progress as compared to a susceptible cultivar. The range of disease severity in the field, ranked on a scale from 0 to 4, was highly and significantly correlated with the percentage of diseased plants. The greenhouse test was unreliable as a predictor of the degree of resistance observed in the field. Similar wilt levels in the greenhouse and the field were found only in susceptible cultivars.     

Infection by Meloidogyne artiellia does not break down resistance to races 0, 1a, and 2 of Fusarium oxysporum f. sp. ciceris in chickpea genotypes

Fusarium oxysporum f. sp. ciceris, and the root-knot nematode Meloidogyne artiellia, coinfect chickpea crops in several countries of the Mediterranean Basin. The influence of root infection by M. artiellia on the reactions of chickpea genotypes with different reaction to infection with F. oxysporum f. sp. ciceris races 0, 1A, and 2 was investigated under controlled environmental conditions. Results demonstrated that co-infection of chickpea genotypes resistant to specific fungal races by M. artiellia did not influence the Fusarium wilt reaction of the plant, irrespective of the F. oxysporum f. sp. ciceris race assayed. However, in some of the assayed combinations, coinfection by both pathogens significantly affected the level of colonization by the fungus or reproduction of the nematode in the root system. Thus, coinfection of chickpea plants with Foc-0 and M. artiellia significantly decreased the level of colonization of the root system by F. oxysporum f. sp. ciceris in genotypes 'CA 336.14.3.0' and 'PV 61', but not in 'ICC 14216 K' and 'UC 27'. Similarly, the nematode reproduction index was also significantly reduced by coinfection with Foc-0 in the four chickpea genotypes tested and inoculated with this race. Conversely, coinfection of chickpea plants with Foc-1A and M. artiellia significantly increased colonization of the root system by the fungus in all genotypes inoculated with this race, except for line BG 212. Altogether, we confirmed the complete resistance phenotype of 'UC 27' and 'ICC 14216 K' to Foc-0, and of 'ICC 14216 K' to Foc-1A and Foc-2, and demonstrated that this resistance was not modified by coinfection of the resistant plant with M. artiellia.     

Genetic diversity in Fusarium oxysporum f.sp. dianthi and Fusarium redolens f.sp. dianthi

Pathogenic isolates were selected representing all known vegetative compatibility groups (VCGs) and races of Fusarium oxysporum sensu lato from Dianthus spp. On basis of differences in the internal transcribed spacer region of the ribosomal DNA, six VCGs were classified as F. oxysporum f.sp. dianthi and four as F. redolens f.sp. dianthi. All VCGs of F. oxysporum f.sp. dianthi were characterized by unique restriction fragment length polymorphisms (RFLPs), unique overall esterase profiles, and unique virulence spectra, supporting a clonal lineage concept. Two VCGs of F. oxysporum f.sp. dianthi nevertheless comprised more than one race, but races within the same VCG shared the same distinct overall virulence spectrum. VCGs belonging to F. redolens f.sp. dianthi also had unique RFLPs and unique virulence spectra, but had grossly identical esterase profiles. Three new races (9, 10 and 11) are described for F. oxysporum f.sp. dianthi, and four for F. redolens f.sp. dianthi. Two races previously considered lost were recovered; race 7 was identified as a member of VCG 0021 of F. oxysporum f.sp. dianthi while race 3 was identified as a distinct VCG and race of F. redolens f.sp. dianthi. A summary of races and VCGs in F. oxysporum f.sp. dianthi and F. redolens f.sp. dianthi is presented.     

Fusarium solani f. sp. cucurbitae race 1, a potential pathogen of grafted watermelon production in Spain*

A crown, root and fruit rot of squash (Cucurbita maxima and Cucurbita moschata) has been observed in eastern provinces of Spain over the past 4 years. Isolations from the crown of symptomatic plants and fruits yielded primarily a Fusarium solani that was identified as F. solani f. sp. cucurbitae race 1 on the basis of pathogenicity tests and disease symptoms in the field. In Spain, more than 90% of watermelon plants are grafted, using different Cucurbita hybrids (C. maxima × C. moschata) as rootstocks. In 1998, some grafted watermelon plants were first found to be affected by F. s. cucurbitae race 1. The purpose of this study was to evaluate the pathogenicity of this fungus on several rootstocks commonly used for grafting watermelon (Brava, Titan, Shintoza, RS‐841, TZ‐148 and TW‐1) in order to prevent a possible spread of this fungus that could cause serious economic losses in watermelon production. None of them proved to be resistant.     

Inheritance of resistance in carnation against Fusarium oxysporum f.sp. dianthi races 1 and 2, in relation to resistance components

Four carnation cultivars, Novada (resistant to races 1 and 2 ofFusarium oxysporum f.sp.dianthi), Elsy (susceptible to race 1), Lena (susceptible to race 2) and Sam's Pride (susceptible to both races), were selfed and crossed. When three months old, the seedlings were inoculated via the roots or via the stems, after which wilting was recorded weekly according to a 5-point ordinal scale.Analyses were carried out on the proportions of diseased plants. For race 1 variation between the progenies could be described by means of general combining abilities only; GCA values were not affected by the inoculation method used. Also for race 2 GCAs were most important but the GCA values appeared different for the two inoculation methods. It is concluded that resistance to both races is inherited in an additive way.Indications for independently inherited root-specific resistance components (extravascular resistance) were only found with race 2. With both races, the ability to confine the pathogen at the infection site appeared the most important resistance component. Resistant progenies were also characterized by longer latent periods and lower wilting rates.Both race 1 and race 2 induced the accumulation of the phytoalexins dianthalexin and methoxydianthramide S, but race 2 induced higher amounts than race 1. The accumulation of phytoalexins was positively correlated to the resistance level of the progenies against the respective races. The progenies of the double-resistant cultivar Novada appeared to produce particularly high levels of phytoalexins.     

Plant defence reactions against fusarium wilt in chickpea induced by incompatible race 0 of Fusarium oxysporum f.sp. ciceris and nonhost isolates of F. oxysporum

Germinated seeds of 'kabuli' chickpea cv. ICCV 4 were inoculated with a conidial suspension of the incompatible race 0 of Fusarium oxysporum f.sp. ciceris (Foc) or of nonhost F. oxysporum resistance 'inducers', and 3 days later were challenged by root dip with a conidial suspension of highly virulent Foc race 5. Prior inoculation with inducers delayed the onset of symptoms and/or significantly reduced the final amount of fusarium wilt caused by race 5. However, the extent of disease suppression varied with the nature of the inducing agent; the nonhost isolates of F. oxysporum were more effective at disease suppression than the incompatible Foc race 0. Inoculation with the inducers gave rise to synthesis of maackiain and medicarpin phytoalexins in inoculated seedlings; these did not accumulate in plant tissues but were released into the inoculum suspension. Inoculation with inducers also resulted in accumulation of chitinase, β-1,3-glucanase and peroxidase activities in plant roots. These defence-related responses were induced more consistently and intensely by nonhost isolates of F. oxysporum than by incompatible Foc race 0. The phytoalexins and, to a lesser extent, the antifungal hydrolases, were also induced after challenge inoculation with Foc race 5. However, in this case the defence responses were induced in both preinduced and noninduced plants infected by the pathogen. It is concluded that the suppression of fusarium wilt in this study possibly involved an inhibitory effect on the pathogen of preinduced plant defences, rather than an increase in the expression of defence mechanisms of preinduced plants following a subsequent challenge inoculation.     

Genetics of resistance to race TTKSK of Puccinia graminis f. sp. tritici in Triticum monococcum

Race TTKSK (or Ug99) of Puccinia graminis f. sp. tritici possesses virulence to several stem rust resistance genes commonly present in wheat cultivars grown worldwide. New variants detected in the race TTKSK lineage further broadened the virulence spectrum. The identification of sources of genetic resistance to race TTKSK and its relatives is necessary to enable the development and deployment of resistant varieties. Accessions of Triticum monococcum, an A-genome diploid wild and cultivated wheat, have previously been characterized as resistant to stem rust. Three resistance genes were identified and introgressed into hexaploid wheat: Sr21, Sr22, and Sr35. The objective of this study was to determine the genetic control and allelic relationships of resistance to race TTKSK in T. monococcum accessions identified through evaluations at the seedling stage. Generation F(2) progeny of 8 crosses between resistant and susceptible accessions and 13 crosses between resistant accessions of T. monococcum were evaluated with race TTKSK and often with North American races, including races QFCSC, TTTTF, and MCCFC. For a selected population segregating for three genes conferring resistance to race TTKSK, F(2:3) progeny were evaluated with races TTKSK, QFCSC, and TTTTF. In that population, we detected two genes conferring resistance to race TTKSK that are different from Sr21, Sr22, and Sr35. One of the new genes was effective to all races tested. The identification of these genes will facilitate the development of varieties with new resistance to race TTKSK.     

Induced resistance in tomato plants against Fusarium wilt invoked by Fusarium oxysporum f.sp. dianthi

Tomato plants, susceptible toFusarium oxysporum f. sp.lycopersici, were inoculated by immersing the roots in a conidial suspension ofF. oxysporum f. sp.lycopersici race 1,F. oxysporum f. sp.dianthi race 2 or a mixture of both fungi. Plants inoculated withF. oxysporum f. sp.lycopersici showed disease symptoms after 2 weeks, whereas plants inoculated withF. oxysporum f. sp.dianthi or a mixture of both fungi remained symptomless for over 7 weeks, the duration of the experiment. In another experiment root systems of plants were split and each half was separately inoculated. One half was firstly inoculated withF. oxysporum f. sp.dianthi or treated with water, followed after a week by a second inoculation of the other half withF. oxysporum f. sp.lycopersici or by a water treatment. The disease symptoms in the half firstly inoculated withF. oxysporum f. sp.dianthi were significantly delayed, compared to plants of which that half had been treated with water. BecauseF. oxysporum f. sp.dianthi reduced disease symptoms caused byF. oxysporum f. sp.lycopersici without any direct interaction with this pathogen, it is concluded thatF. oxysporum f. sp.dianthi is able to induce resistance againstF. oxysporum f. sp.lycopersici in tomato plants.     

Involvement of phenol metabolism in resistance of Dianthus caryophyllus to Fusarium oxysporum f.sp. dianthi

Three carnation cultivars were investigated for the effect of stem inoculation withFusarium oxysporum f.sp.dianthi on production of phenolic compounds and on fungistatic activity. Carnation stems were characterized by a complex mixture of cell wall-bound phenolics, several of which occurred in considerable amounts. Only very low amounts of phenolic compound were present in the vacuoles.Infection withF. oxysporum f.sp.dianthi induced the production and accumulation of a number of new compounds, both free in the cell sap and bound to the cell wall. In addition, the stem extracts acquired germination-inhibiting properties for conidia of the fungus. The accumulation of several phenolics and the fungistatic activity were roughly correlated to the degree of resistance of the three cultivars. Part of the differences in their resistance toF. oxysporum f.sp.dianthi might be due to an inhibition of the conversion of phenolic acid-type precursors into phytoalexins in the more susceptible cultivars.Samenvatting Drie anjercultivars werden onderzocht op de effecten van stengelinoculatie metFusarium oxysporum f.sp.dianthi op de produktie van fenolische verbindingen en op de fungistatische activiteit van stengelextracten. Anjerstengels bleken een complex mengsel van celwand-gebonden fenolzuren te bevatten, waarvan er verschillende in vrij grote hoeveelheden voorkwamen. Daartegenover waren de hoeveelheden fenolische verbindingen in de vacuole bij gezonde anjerstengels erg laag.Infectie metF. oxysporum f.sp.dianthi induceerde de produktie en accumulatie van een aantal nieuwe verbindingen in het celsap, alsook gebonden aan de celwand. Tevens bleek de remming van de kieming van conidiën vanF. oxysporum f.sp.dianthi onder invloed van deze stengelextracten sterk verhoogd, in vergelijking met de remming veroorzaakt door extracten van gezonde stengels. De accumulatie van een aantal fenolen en de verhoging van de fungistatische activiteit van de extracten waren in grote lijnen gecorreleerd met de uit de praktijk bekende resistentie van de drie cultivars. De verschillen in resistentie tegenF. oxysporum f.sp.dianthi zouden deels kunnen berusten op remming van de omzetting van precursors (fenolzuren) in fytoalexinen in de meer vatbare cultivars.     

Potential role for salicylic acid in induced resistance of asparagus roots to Fusarium oxysporum f.sp. asparagi

Pre-inoculation of asparagus ( Asparagus officinalis ) roots with selected nonpathogenic isolates of Fusarium oxysporum (np Fo ) has previously been shown to induce systemic resistance against infection by F. oxysporum f.sp. asparagi ( Foa ) through activation of plant-defence mechanisms. To elucidate the putative np Fo -mediated defence pathways, the effect of salicylic acid (SA) was examined in a split-root system of asparagus where one half of the seedling root system was drenched with SA and the activation of defence responses was measured subsequently on the remaining roots. SA-treated plants exhibited enhanced systemic resistance, with a significant reduction in disease severity of the roots inoculated with Foa , compared with untreated plants. SA activated peroxidase and phenylalanine ammonia-lyase, as well as lignification, upon Foa attack, in a manner similar to that observed with np Fo pretreatment. In addition, application of diphenyleneiodonium, an SA biosynthesis inhibitor, led to failure of np Fo to induce lignin deposition and systemic resistance. Treatment of fungal spores with SA did not affect germination and growth of either np Fo or Foa in in vitro antifungal assays. Production of SA at the site of np Fo infection may be involved in the induction of Foa resistance in asparagus roots.     

A detailed evaluation method to identify sources of quantitative resistance to Fusarium oxysporum f. sp. pisi race 2 within a Pisum spp. germplasm collection

Fusarium oxysporum f. sp. pisi (Fop) is an important pathogen of field pea (Pisum sativum) worldwide. The constant evolution of the pathogen drives the necessity to broaden the genetic basis of resistance to Fop. To achieve this, it is important to have a large germplasm collection available and an accurate and efficient method for disease assessment. Here, a detailed evaluation method coupling disease incidence, disease rating over time and its related area under the disease progression curve (AUDPC) was established and used to screen a Pisum spp. germplasm collection against one isolate of Fop race 2. A large variation in the disease response of specific pea accessions ranging from highly resistant to susceptible was observed within the collection, indicating the quantitative expression of the resistance. The repetition of the inoculation experiments on a subset of 19 accessions, including two susceptible accessions, indicated that the scoring method was robust and reproducible and confirmed the highly resistant phenotypes of 11 accessions. To initiate the characterization of resistance mechanisms within these accessions, the external and internal stem symptoms were compared between these selected pea accessions, together with the extent of fungal colonization within plants. All these tests indicated that, in all resistant accessions, the resistance mechanisms efficiently stopped pathogen progression at the crown. Incorporation of these sources of resistance to breeding programmes will contribute to improved Fop resistance in pea cultivars.     

Pathogenic variability in Ethiopian isolates of Fusarium oxysporum f. sp. ciceris and reaction of chickpea improved varieties to the isolates

Twenty-four isolates of Fusarium oxysporum f. sp. ciceris were isolated from wilted chickpea plants obtained from different districts and ‘wilt sickplots’ of central Ethiopia to assess variability in pathogenecity of the populations. Each isolate was tested on 10 different chickpea lines and eight improved chickpea varieties. Isolates showed highly significant variation in wilt severity on the differential lines and improved varieties. Based on the reaction types induced on differential lines, isolates were grouped into four corresponding races. Of the 24 isolates, F13, F20 and F22 were the most virulent. Isolates of race 3 were found in all of the districts and ‘wilt sickplots’ studied. Improved chickpea varieties also showed differential reactions to the isolates. All varieties were resistant to isolates of race 3, while varieties Arerti and DZ-10-4 were resistant to all isolates tested, showing the lowest mean wilt severity. Varieties DZ-10-11 and Maryie were susceptible to isolates F13, F20 and F22 and showed the highest mean wilt severity. Identification of races can be useful in breeding chickpea varieties resistant to wilt. The differential reactions of the improved varieties against different races might be important in managing chickpea wilt through gene deployment.