Mating Behaviour and Vegetative Compatibility in Spanish Populations of Botryotinia fuckeliana

Mating behaviour and vegetative compatibility were studied in Spanish populations of Botryotinia fuckeliana. Fifty-seven isolates out of the 61 tested were sexually fertile with one or more of the reference strains of known mating type (MAT1-1 or MAT1-2). Thirty-nine isolates were heterothallic, giving fertile crosses when mated with the MAT1-1 (24 isolates) or the MAT1-2 (15 isolates) reference strain. Eighteen isolates crossed successfully with both MAT1-1 and MAT1-2 reference strains, and were referred to as homothallic or MAT1-1/2. Both mating types were widespread, being represented in isolates from two regions, from the same and different greenhouses, from different hosts, and from different years of isolation. Isolates were paired on Malt Extract Agar + NaCl to evaluate vegetative compatibility. Most of the paired isolates were unable to fuse and showed a different reaction of incompatibility. Nitrate-non-utilising (nit) mutants were selected by growth on a medium amended with 30–50gl^–1 potassium chlorate. Over 600 chlorate-resistant sectors were recovered from 40 isolates at a mean frequency of 0.15–2.39 sectors per colony, but only 11% were identified as nit mutants by their thin growth with no aerial mycelium on minimal medium. However, most of these nit mutants reverted to wild type during six months of storage on chlorate-amended medium. Genetic complementation between nit mutants occurred only in two cases between mutants from the same isolate.     

Improved Medium for Selecting Nitrate-Nonutilizing (nit) Mutants of Verticillium dahliae

ABSTRACT Nitrate-nonutilizing (nit) mutants are commonly used to determine vegetative compatibility between isolates of Verticillium dahliae by complementation (heterokaryon) testing. These mutants emerge spontaneously as chlorate-resistant sectors growing out of partially restricted, wild-type colonies on chlorate-amended media. The commonly used chlorate media are based on minimal medium (MMC) or cornmeal agar (CMC), amended with potassium chlorate. nit mutants recovered on these media constituted 10 to 36%(on MMC) and 25 to 45%(on CMC) of the apparently resistant sectors. An improved water agar chlorate medium (WAC) is described that is more effective for selecting chlorate-resistant nit mutants. WAC medium consists of agar (2%), glucose (0.02%), and potassium chlorate (2 to 5%). On WAC, growth of most V. dahliae isolates was strongly inhibited, and 66 to 100%(average >80%) of the chlorate-resistant sectors formed were nit mutants. Most mutants were characterized as nit1, and about 6% as NitM.     

Cultural Characteristics, Pathogenicity and Vegetative Compatibility of Fusarium udum Isolates from Pigeonpea (Cajanus cajan (L.) Millsp.) in Kenya

Seventy-nine single-spore isolates of Fusarium udum, the causal agent of wilt disease of pigeonpea, from Kenya, India and Malawi were characterized according to their cultural characteristics, pathogenicity and vegetative compatibility group (VCG). The isolates exhibited high variation in pathogenicity on a wilt-susceptible pigeonpea variety, and in mycelial growth and sporulation on potato dextrose agar medium. The 79 isolates were categorized into two virulence groups, two groups of radial mycelial growth and four groups of sporulation. Radial mycelial growth showed a moderate negative correlation (r = –0.40; P = 0.01) with sporulation. However, mycelial growth and sporulation had no correlation with virulence. Pairings between complementary nitrate non-utilizing (nit) mutants of F. udum generated on chlorate containing minimal medium revealed that all the isolates belonged to a single VCG (VCG 1) with two subgroups, VCG 1 I and VCG 1 II. Vegetative compatibility was independent of cultural characteristics and pathogenicity. This is the first report of vegetative compatibility in F. udum.     

Vegetative compatibility grouping in Botrytis cinerea using sulphate non-utilizing mutants

Twenty-one strains of Botrytis cinerea isolated from six plant species on ten sites throughout Israel, as well as a strain from France, were tested for vegetative and mycelial incompatibility, pathogenicity, resistance to the fungicides carbendazim and iprodione, and colony morphology. Selenate-resistant mutants were isolated from the strains as spontaneous, fast-growing sectors arising from restricted colonies on medium amended with sodium selenate with a mean frequency of 0.04 sectors/colony; 81% of the sectors were sulphate non-utilizing (sul) mutants. One hundred and four sul mutants were divided into two complementary groups: resistant (66 mutants) and sensitive to chromate. Based on compatibility reactions between chromate-resistant and chromate-sensitive sul mutants, 12 strains were compatible only with themselves and were each classified as belonging to different vegetative compatibility groups (VCGs). Nine strains were each compatible with one to three other strains, and were assembled into three multi-member VCGs. Mycelial incompatibility between wild-type strains (barrage), in the form of a zone of dark pigmentation or sparse mycelium with or without dark pigmentation of the agar along the line of confrontation, was observed for 70% of the inter-strain pairings. There was no correspondence in compatibility between strains revealed by two approaches: strains in different VCGs did not necessarily produce a barrage. However, self-compatibility was observed both as heterokaryon formation between complementary sul mutants and as an absence of barrages between mycelia of wild-type strains; wild-type strains belonging to the same VCG did not exhibit strong barrages, although weak antagonistic reactions were observed. Strains in two multi-member VCGs showed the same patterns of resistance to carbendazim and iprodione; the third multi-member VCG contained isolates with different patterns of resistance. Four morphological types were revealed among wild-type strains: conidial (five strains), sclerotial (six strains), intermediate (ten strains), and mycelial (one strain). On bean leaves, conidial strains were more aggressive than sclerotial strains.     

灰葡萄孢菌nit突变体的诱导及其在营养体亲和性测定中的应用初探

 从山西运城、临汾、长治、晋中、大同等地保护地黄瓜灰霉病病株上采集、分离的分属于3个不同菌丝融合群的8个灰葡萄孢菌单孢菌株,经氯酸盐诱导处理,共获得了抗氯酸盐的硝酸盐利用缺陷突变体(nit突变体)59株,其中nit1型38株,nit3型10株,nitM型11株。所有nit突变株分别在PDA斜面转管培养3次(21 d)后,除6株恢复成野生菌株外,其余多数nit突变菌株表现稳定。来源于同一野生菌株的不同类型nit突变体间或同一菌丝融合群不同野生菌株的nit突变体间可产生互补反应而形成异核体,其中以nitM型突变株互补性最好,在利用nit突变体测定灰葡萄孢菌营养体亲和性时应作为标准菌株。来源于不同菌丝融合群的nit突变体间不能产生互补反应。     

Reassessment of vegetative compatibility of Sclerotinia homoeocarpa using nitrate-nonutilizing mutants

Nitrate-nonutilizing (nit) mutants were recovered for the first time from 21 isolates of Sclerotinia homoeocarpa collected in the United States. Mutants were selected from shredded mycelium of each isolate when cultured on water agar medium amended with 4% (wt/vol) potassium chlorate. The mutants could be classified into three phenotypes: nit1, nit3, and NitM, based on their growth on minimal medium (Czapek solution agar) supplemented with NaNO(2) or hypoxanthine. Complementary heterokaryons were observed in pairings between different phenotypes of nit mutants derived from compatible isolates, but not in self-fusions or pairings between incompatible isolates. The vigor of prototrophic growth varied with isolates and mutant phenotypes. Strong and continuous heterokaryons, as well as weak and spontaneous ones, formed depending on pairings of nit mutants. Stable heterokaryons between compatible isolates, but apoptotic reactions between incompatible isolates, were observed immediately after hyphal fusion under the epifluorescence microscope. The 21 isolates used in this study, which were previously assigned into 11 different vegetative compatibility groups (VCGs) based on the formation of a barrage zone at the contact site of paired isolates on complete medium (potato dextrose agar), were regrouped into five VCGs based on heterokaryon formation between nit mutants on minimal medium.     

瓜类尖孢镰刀菌的营养体亲和群研究

 应用营养亲和性方法研究了尖孢镰刀菌菌株抗氯酸盐突变体和nit突变体的诱发规律及分布特性,以及菌株营养体亲和群(VCG)的划分。研究表明,不同寄主(黄瓜、甜瓜和西瓜)分离的尖孢镰刀菌菌株形成的抗氯酸盐突变体数目差异不显著,平均为每个接种点产生0.89~0.98个;但寄主不同部位(根部、茎基部和茎中部)分离的菌株间差异显著,形成的数目分别为1.27、0.75及0.76个。菌株产生的nit1突变体比例(75.40%)显著高于nitM突变体比例(13.17%);nit1突变体数目会因菌株的寄主及菌株寄主部位的不同而有差异,寄主为黄瓜、甜瓜和西瓜的菌株产生的比例依次为67.73%、83.71%和77.50%,根部、茎基部及茎中部分离菌株产生的比例依次为81.82%、78.48%和68.64%,而在致病菌株与非致病菌株间无显著差异,分别为74.43%和79.63%;nitM突变体数目受菌株寄主影响较小,所占比例在11.17%~13.92%之间;而在寄主不同部位分离的菌株及致病菌株与非致病菌株间差异显著,分离自茎基部的菌株所占比例最高为15.97%,茎中部菌株所占比例最低为9.87%,致病菌株与非致病菌株所占比例分别为14.08%和9.26%。供试菌株分为7个VCGs,其特点为来源于不同寄主的尖孢镰刀菌菌株互不亲和,同一寄主的致病菌株与非致病菌株均不亲和,同一寄主不同部位分离的菌株可亲和。     

Vegetative compatibility and heterokaryon stability in Fusarium oxysporum f.sp. radicis-lycopersici from Italy

Fusarium crown and root rot, caused by Fusarium oxysporum f.sp. radicis-lycopersici ( Forl ), is one of the most destructive soilborne diseases of tomato in Italy. Chlorate-resistant, nitrate-nonutilizing ( nit ) mutants were used to determine vegetative compatibility among 191 isolates of Forl collected in five geographic regions (Calabria, Emilia-Romagna, Liguria, Sardinia, Sicily) in Italy. The isolates were assigned to five vegetative compatibility groups (VCGs): 65 isolates to VCG 0090; 99 to VCG 0091; 23 to VCG 0092; two to VCG 0093; and two to VCG 0096. The population structure of Forl in Italy is similar to that reported for Israel, and differs from that found in North Atlantic European countries, where VCG 0094 is predominant. The stability of prototrophic heterokaryons originating from hyphal anastomosis between compatible complementary nit mutants was assessed through conidial analysis and mycelial mass transfer. Most monoconidial cultures (84%) recovered from 117 prototrophic heterokaryons were nit mutants, indicating that heterokaryons generally do not proliferate well through conidiation; most of the 177 prototrophic heterokaryons examined were unstable, and only 9% sustained prototrophic growth through the tenth mycelial transfer upon subculturing. The prototrophic growth is proposed to be maintained through restoration of the heterokaryotic state by continual anastomosis between adjacent homokaryotic hyphae. Since heterokaryosis is a prerequisite for parasexual recombination, we speculate that this mechanism is unlikely to play a major role in generating the VCG diversity found among Forl or other strains of F. oxysporum.     

新月弯孢菌营养体亲和群鉴定方法探讨

 采用菌株直接配对、显微镜观察菌丝融合和硝酸盐缺陷型(nit)突变体互补测试法,对44个来自不同地区的玉米弯孢菌叶斑病叶中的新月弯孢菌(Curvularia lunata)菌株进行了营养体亲和性分析。在野生型菌株的两两配对中,C.lunata菌株接触产生4种反应类型,但无明显的抗衡反应产生。在菌丝融合显微观察中,光学显微镜下只见大多数菌丝反应为一菌丝向另一菌丝无限靠近,未见融合,但在电子显微镜下,发现两菌丝细胞已不再是独立的。这些结果表明,因两菌落间的抗衡反应和菌丝融合特征都不明显,故不宜采用直接配对和显微观察来划分C.lunata的营养体亲和群。在nit突变体互补测试中,菌株在KClO₃浓度1.5%~3.0%的KPS中诱导表明,2.0%~3.0% KClO₃适宜于大多数菌株。抗氯酸盐突变体在Czapek培养基中能鉴定出nit突变体,但在MM上却不能。全部3640抗氯酸盐突变体在Czapek中共鉴定出2 40个稳定的nit突变体,其中nit1占59.2%,nit3占39.2%,NitM占0.8%,nit D (3种氮源都不能利用)占0.8%。44个菌株中,24个(55%)获得了nit突变体,20个(45%)还没有,仅2个菌株(124和155)各获得了1个NitM突变体。各菌株突变体类型间只有NitM与nit1或nit3是异核亲和的,其余均不能产生亲和反应。菌株124和155都是营养体自身亲和菌株。用2个NitM作测试菌株,初步划分出2个VCGs,5个归入VCG1,另有5个归入VCG2,其它菌株因未获得NitM或nit突变体还不能鉴定。以上结果表明,硝酸盐缺陷型突变体互补测试法可用于鉴定C.lunata菌株的营养体亲和群。     

Sexual Recombination in Gibberella zeae

ABSTRACT We developed a method for inducing sexual outcrosses in the homothallic Ascomycete fungus Gibberella zeae (anamorph: Fusarium graminearum). Strains were marked with different nitrate nonutilizing (nit) mutations, and vegetative compatibility groups served as additional markers in some crosses. Strains with complementary nit mutations were cocultured on carrot agar plates. Ascospores from individual perithecia were plated on a minimal medium (MM) containing nitrate as the sole nitrogen source. Crosses between different nit mutants segregated in expected ratios (3:1 nit(-):nit(+)) from heterozygous perithecia. Analysis of vegetative compatibility groups of progeny of two crosses indicated two and three vegetative incompatibility (vic) genes segregating, respectively. For rapid testing of sexual recombination between nit mutants, perithecia were inverted over MM to deposit actively discharged ascospores. Development of proto-trophic wild-type colonies was taken as evidence of sexual recombination. Strains of G. zeae group 2 from Japan, Nepal, and South Africa, and from Indiana, Kansas, and Ohio in the United States were sexually interfertile. Four group 1 strains were not interfertile among themselves or with seven group 2 strains. Attempts to cross G. zeae with representatives of F. acuminatum, F. avenaceum, F. culmorum, F. crookwellense, F. oxysporum, and three mating populations of G. fujikuroi were not successful.     

尖孢镰孢(Fusarium oxysporum)硝酸盐营养突变株及其营养体亲和性

从荸荠、棉花、西瓜、黄瓜、胡瓜、大豆、花生等12种寄主作物上获得尖孢镰孢(F—usarium oxysporum)菌株20个,已知15个菌株分属于6个专化型。所有20个菌株在含有氯酸盐的培养基上产生抗氯酸盐的突变体,其突变体在以硝酸盐作为氮源的培养基上表现为无气生菌丝生长,即不能利用硝酸盐的突变株(nit),共获得nit突变株181个。同一专化型的nit突变株之间在以硝酸盐为氮源的培养基上配对时,在菌丝接触处可产生互补作用,即营养体亲和性,表现为旺盛气生菌丝生长。不同专化型的nit突变株之间则不能互补产生异核体而表现为非亲和性仍为突变型生长。每个菌株均获得能产生互补作用的nit突变株。根据营养体亲和性反应,20个菌株归入13个营养体亲和群(VCG),并显示出VCGs与菌株专化型之间的相关性。nit突变株在一般条件下是稳定的,而且某些nit株的亲和能力特强。     

Vegetative Compatibility and Mycotoxin Chemotypes among Fusarium graminearum (Gibberella zeae) Isolates from Wheat in Argentina

Gibberella zeae (anamorph Fusarium graminearum) is the main pathogen causing Fusarium head blight of wheat in Argentina. The objective of this study was to determine the vegetative compatibility groups (VCGs) and mycotoxin production (deoxynivalenol, nivalenol and 3-acetyl deoxynivalenol) by F. graminearum populations isolated from wheat in Argentina. VCGs were determined among 70 strains of F. graminearum isolated from three localities in Argentina, using nitrate non-utilizing (nit) mutants. Out of 367 nit mutants generated, 41% utilized both nitrite and hypoxanthine (nit1), 45% utilized hypoxanthine but not nitrite (nit3), 9% utilized nitrite but not hypoxanthine (NitM) and 5% utilized all the nitrogen sources (crn). The complementations were done by pairing the mutants on nitrate medium. Fifty-five different VCGs were identified and the overall VCG diversity (number of VCGs/number of isolates) averaged over the three locations was 0.78. Forty-eight strains were incompatible with all others, thus each of these strains constituted a unique VCG. Twenty-two strains were compatible with other isolates and were grouped in seven multimembers VCGs. Considering each population separately, the VCG diversity was 0.84, 0.81 and 1.0 for San Antonio de Areco, Alberti and Marcos Juarez, respectively. Toxin analysis revealed that of the 70 strains of F. graminearum tested, only 90% produced deoxynivalenol, 10% were able to produce deoxynivalenol and very low amounts of 3-acetyldeoxynivalenol. No isolate produced nivalenol. The results indicate a high degree of VCG diversity in the F. graminearum populations from wheat in Argentina. This diversity should be considered when screening wheat germplasm for Fusarium head blight resistance.     

福建省香蕉枯萎病菌硝酸盐营养突变体的营养体亲和性测定

 Fourteen strains of Fusarium oxysporum f. sp. cubense were induced to produce 146 nitrate-nonutilizing(nit) mutants on a chlorate-containing medium. Among them, there were 117 nit1 mutants(80.14%), 17 nit3 mutants(11.64%) and 12 nitM mutants(8.22%). These strains were divided into two vegetative compatibility groups(VCGs) by the vegetative compatibility tests. Twelve strains of F. oxysporum f. sp. cubense from Musa AAA belonged to VCG1, two trains from Musa ABB belonged to VCG2.     

Physiological Races and Vegetative Compatibility Groups of Fusarium oxysporum f. sp. lactucae Isolated from Crisphead Lettuce in Japan

One hundred and sixteen isolates of Fusarium oxysporum f. sp. lactucae obtained from 85 fields in three crisphead lettuce-producing areas in Nagano Prefecture, Japan were typed for races using differential cultivars Patriot, Banchu Red Fire and Costa Rica No. 4. They were also grouped into vegetative compatibility groups (VCGs) using complementation tests with nitrate non-utilizing (nit) mutants. Two California strains reported as F. oxysporum f. sp. lactucum, a type culture of F. oxysporum f. sp. lactucae, and 28 avirulent isolates of F. oxysporum obtained from crisphead lettuce were included for comparison. Among Nagano isolates, 66 isolates were identified as race 1, and 50 as race 2. Race 1 strains derived from Shiojiri and Komoro cities and race 2 from Kawakami village and Komoro city. All isolates of race 2 were biotin auxotrophs, and the race could be distinguished based on its requirement for biotin on minimal nitrate agar medium (MM). Pathogenic isolates were classified into two VCGs and three heterokaryon self-incompatible isolates. Strong correlations were found between race and VCG. All the race 1 strains were assigned to VCG 1 except self-incompatible isolates, and all the race 2 strains to VCG 2. The 28 avirulent isolates of F. oxysporum were incompatible with VCG 1 and VCG 2. California strains was vegetatively compatible with VCG 1, and they were assigned to race 1. Based on vegetative compatibility, these two races of F. oxysporum f. sp. lactucae may be genetically distinct, and F. oxysporum f. sp. lactucae race 1 is identical to F. oxysporum f. sp. lactucum. Received 7 May 2002/ Accepted in revised form 6 September 2002     

Vegetative Compatibility amongVerticillium dahliae Isolates from Watermelon in Greece

Vegetative compatibility among 17 isolates ofVerticillium dahliae obtained from watermelon, originating from eight regions of Greece, was investigated using complementation tests between nitrate-nonutilizing(nit) mutants. Among 529 chlorate-resistant sectors obtained, only 107 werenit mutants. These mutants were paired with tester strains (from Greece and other countries) of previously described vegetative compatibility groups (VCGs), and also were paired in many combinations among themselves. All isolates were self-compatible. Sixteen isolates were found to belong to VCG2. Only isolate V75 could not be assigned to a VCG, because the threenit mutants obtained from it showed negative reactions with the tester strains of four VCGs and with complementary mutants from other isolates. Based on this sample, we conclude that the population ofV. dahliae from watermelon in Greece is homogeneous in respect to VCG.     

尖孢镰孢(Fusarium oxysporum)硝酸盐营养突变株及其营养体亲和性

 从荸荠、棉花、西瓜、黄瓜、胡瓜、大豆、花生等12种寄主作物上获得尖孢镰孢(F-usarium oxysporum)菌株20个,已知15个菌株分属于6个专化型。所有20个菌株在含有氯酸盐的培养基上产生抗氯酸盐的突变体,其突变体在以硝酸盐作为氮源的培养基上表现为无气生菌丝生长,即不能利用硝酸盐的突变株(nit),共获得nit突变株181个。同一专化型的nit突变株之间在以硝酸盐为氮源的培养基上配对时,在菌丝接触处可产生互补作用,即营养体亲和性,表现为旺盛气生菌丝生长。不同专化型的nit突变株之间则不能互补产生异核体而表现为非亲和性仍为突变型生长。每个菌株均获得能产生互补作用的nit突变株。根据营养体亲和性反应,20个菌株归入13个营养体亲和群(VCG),并显示出VCGs与菌株专化型之间的相关性。nit突变株在一般条件下是稳定的,而且某些nit株的亲和能力特强。     

Genotypic diversity in a South African population of the pitch canker fungus Fusarium subglutinans f.sp. pini

The genotypic diversity in a South African population of Fusarium subglutinans f.sp. pini ( F.s. pini ) was determined, based on the number of vegetative compatibility groups (VCGs). Isolates of F.s. pini from South Africa (69), California (five) and Florida (19) were included in the study. The nit1 (or nit3 ) and NitM mutants were selected as chlorate resistant sectors and paired on minimal medium. The South African isolates of F.s. pini were assigned to 23 different VCGs. No heterokaryons formed between isolates from South Africa, California and Florida. The high degree of genotypic diversity in the South African population of F.s. pini is probably due to some level of sexual reproduction in the population.     

A major gene controlling pathogenicity inBotryotinia fuckeliana(Botrytis cinerea)

Non-aggressive mutants were isolated from a single-ascospore strain ofBotryotinia fuckelianafollowing ultraviolet and chemical mutagenesis of conidia and screening on French bean leaves (Phaseolus vulgaris). Crosses with reference strain SAS56 revealed one ultraviolet induced mutant (Mp97) in which the non-aggressive phenotype segregated 1:1 indicating control by a single gene with a major effect on pathogenicity. Further crosses showed that this gene, designatedPat1, is not linked toMbc1(benzimidazole resistance),Daf1(dicarboximide resistance),nit1(nitrate non-utilising), orSel1(sodium selenate resistance). The pathogenicity ofPat1strains was compared with various wild-type strains. Mutant strains produced small, restricted lesions on leaves of French bean and soybean (Glycine max) and slowly spreading lesions on rose (Rosaspp.) flowers. The mutant was essentially non-pathogenic on tomato stems at 20 and 25 °C but produced a few invasive infections at 10 and 15 °C. Tests of radial growth rate, sporulation and sclerotial production showed thatPat1strains exhibit no gross unfitness or unusual nutrient requirement. Althoughin vivostudies showed substantially less total polygalacturonase activity inPat1lesions compared to those produced by wild-type strains, differences in polygalacturonase isozyme profiles were not correlated with the presence ofPat1.Pat1strains showed relatively low acid production in pH indicator medium. Microscopic examination showed that lesions induced by the Mp97 mutant on French and soybean leaves (4 days old), but not by its parent, were surrounded by a distinct staining zone of mesophyll cells suggesting a difference in host response. However, no differences in phytoalexin induction were found in a soybean assay.     

Genetic analysis and molecular characterisation of laboratory and field mutants of Botryotinia fuckeliana (Botrytis cinerea) resistant to QoI fungicides

BACKGROUND: QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz. exhibiting in vitro reduced sensitivity to trifloxystrobin. RESULTS: B. fuckeliana mutants highly resistant to trifloxystrobin were obtained in the laboratory by spontaneous mutations in wild‐type strains, or from naturally infected plants on a medium amended with 1–3 mg L^?1 trifloxystrobin and 2 mM salicylhydroxamic acid, an inhibitor of alternative oxidase. No point mutations were detected, either in the complete nucleotide sequences of the cytb gene or in those of the aox and Rieske protein genes of laboratory mutants, whereas all field mutants carried the G143A mutation in the mitochondrial cytb gene. QoI resistance was always maternally inherited in ascospore progeny of sexual crosses of field mutants with sensitive reference strains. CONCLUSIONS: The G143A mutation in cytb gene is confirmed to be responsible for field resistance to QoIs in B. fuckeliana. Maternal inheritance of resistance to QoIs in progeny of sexual crosses confirmed that it is caused by extranuclear genetic determinants. In laboratory mutants the heteroplasmic state of mutated mitochondria could likely hamper the G143A detection, otherwise other gene(s) underlying different mechanisms of resistance could be involved. Copyright © 2012 Society of Chemical Industry     

Vegetative compatibility and pathogenicity of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> isolates from chrysanthemum in Turkey

A collection of 30 strains of Verticillium dahliae, recovered during 2004–2006 from 12 cultivars of chrysanthemum (Chrysanthemum morifolium) in five districts of İzmir province in Turkey, was assigned to vegetative compatibility groups (VCGs) based on pairings of complementary nitrate-nonutilizing (nit) mutants induced on a chlorate-containing medium. Of these strains, nine were assigned to VCG1, seven to VCG2A, 11 toVCG2B and one to VCG4B. The remaining two strains could not be tested for vegetative compatibility because of their inability to yield nit mutants. Pathogenicity tests conducted by the root-dip method, demonstrated that wilt of chrysanthemum in Turkey is caused by V. dahliae, and most strains in VCG1 were significantly more aggressive to chrysanthemum than those in VCGs 2 and 4B. This is the first known study in the world of the VCGs of V. dahliae isolates from chrysanthemum.