Isolates In Vegetative Compatibility Groups Research Articles

VEGETATIVE COMPATIBILITY GROUPS OF PHYSIOLOGICAL RACES OF PYRICULARIA GRISEA IN Egypt

One hundred forty Pyricularia grisea isolates were collected from the six main rice growing governorates; Kafrelsheikh, Beheira, Sharkia, Gharbia, Dakahlia and Damietta, and from different research stations during 2008, 2009 and 2010 growing seasons. The isolates were identified to their group races as IA (1); IB (12); IC (15); ID (45); IE (1); IF (4); IG (22); IH (32) and II (8) using the international differential varieties under greenhouse conditions. Vegetative compatibility groups (VCGs) among the races were studied through producing nitrate nonutilizing (nit) mutants for the races on chlorate minimal medium (CMM). The results revealed that the nit mutants were grouped into eight VCGs. VCG 1 included members of the IB race group (70.59 %). VCG 2 included members of IC race group with 87.5% and two isolates were identified as IH and II. The largest group, VCG 3 included 44 isolates, most of these isolates were identified as ID (86.36 %). All isolates in VCG 4 were identified as IF. 95.65% of isolates in VCG 5 represented IG and one belonged to II (4.35%). All isolates in VCG 6 corresponded to IH (96.43 %), and only one as ID. VCG 7 included eight isolates, 5 isolates represented ID and one each of IG, IF and IH. Only one isolate was identified as IE race group in VCG 8. The reaction among different nit mutants was examined using a scanning electron microscope and revealed that heterokaryon, incompatibility and inhibition zone were observed. This investigation revealed that the correspondence between VCGs and races ranged from 62.5 to 100 %; however, the latter percentage was relevant to very small number of isolates

Characterization of a Regional Population ofFusarium oxysporumf. sp.niveumby Race, Cross Pathogenicity, and Vegetative Compatibility

ABSTRACT Eighty-eight isolates of Fusarium oxysporum f. sp. niveum, collected from wilted watermelon plants and infested soil in Maryland and Dela-ware, were characterized by cross pathogenicity to muskmelon, race, and vegetative compatibility. Four isolates (4.5%) were moderately pathogenic to >/=2 of 18 muskmelon cultivars in a greenhouse test, and one representative isolate also was slightly pathogenic in field microplots. The four isolates all were designated as race 2, and were in vegetative compatibility group (VCG) 0082. Of the 74 isolates to which a VCG could be assigned, 41 were in VCG 0080, the VCG distributed most widely; 27 were in VCG 0082, and were distributed in half of the 20 watermelon fields surveyed; and 6 were in the newly described VCG 0083, and were restricted to three fields. Among the isolates in VCG 0080, 8 were designated as race 0, 21 as race 1, and 12 as race 2. Of the isolates in VCG 0082, 6 were designated as race 0, 11 as race 1, and 10 as race 2. All isolates in VCG 0083 were designated as race 2. Isolates from more than one race within the same VCG or isolates from more than one VCG were recovered from single plants and fields. No differences in aggressiveness on differential watermelon cultivars were observed among isolates from different VCGs of the same race. A diverse association between virulence and VCG throughout the Mid-Atlantic region suggests that the pathotypes of F. oxysporum f. sp. niveum may be of local origin or at least long existent in the region.

Molecular characterisation of vegetative compatibility groups in Fusarium oxysporum f. sp. radicis-lycopersici and f. sp. lycopersici by random amplification of polymorphic DNA and microsatellite-primed PCR

Random amplification of polymorphic DNA (RAPD-PCR) analysis was conducted on 48 isolates of Fusarium oxysporum f. sp. radicis-lycopersici (F.o.r.l.) from different geographic regions, representing all known vegetative compatibility groups (VCGs) except VCG 0097 and VCG 0099 and on eight isolates of F.oxysporum f. sp. lycopersici (F.o.l.), representing VCGs 0030, 0031, 0032 and 0033. Upon UPGMA (unweighted pair-group method with arithmetic averages) analysis of 86 RAPD-PCR markers generated by 16 informative primers and 44 markers obtained with eight microsatellite primers, a close relatedness was evident for F.o.r.l. isolates in VCGs 0090, 0092, 0096, and, to a lesser extent, for those in VCG 0093. Representatives of VCG 0091 formed a distinct group, while F.o.r.l. isolates in VCGs 0094 and 0098 were not distinguishable by the tested markers, most of which were also shared by F.o.l. isolates belonging to VCGs 0031 and 0033. F.o.l. isolates in VCGs 0030 and 0032 shared most of the molecular markers. The correlation between RAPD-PCR and microsatellite genetic distance was highly significant (R2 = 0.77; P by Mantel test < 0.001). The molecular variability observed in both formae speciales is discussed in relation to the development of F.o.r.l.- and F.o.l.-specific diagnostic tools.

Origin of Race 3 of Fusarium oxysporum f. sp. lycopersici at a Single Site in California

ABSTRACT Thirty-nine isolates of Fusarium oxysporum were collected from tomato plants displaying wilt symptoms in a field in California 2 years after F. oxysporum f. sp. lycopersici race 3 was first observed at that location. These and other isolates of F. oxysporum f. sp. lycopersici were characterized by pathogenicity, race, and vegetative compatibility group (VCG). Of the 39 California isolates, 22 were in VCG 0030, 11 in VCG 0031, and six in the newly described VCG 0035. Among the isolates in VCG 0030, 13 were race 3, and nine were race 2. Of the isolates in VCG 0031, seven were race 2, one was race 1, and three were nonpathogenic to tomato. All six isolates in VCG 0035 were race 2. Restriction fragment length polymorphisms (RFLPs) and sequencing of the intergenic spacer (IGS) region of rDNA identified five IGS RFLP haplotypes, which coincided with VCGs, among 60 isolates of F. oxysporum from tomato. Five race 3 isolates from California were of the same genomic DNA RFLP haplotype as a race 2 isolate from the same location, and all 13 race 3 isolates clustered together into a subgroup in the neighbor joining tree. Collective evidence suggests that race 3 in California originated from the local race 2 population.

Current status and impact of mango malformation in Egypt

A survey was conducted in 1998 to determine the status and impact of mango malformation in Egypt. In the El Giza, Ismailîa and Sharkaia Governerates, disease incidence and severity ranged from 20 to 100% and from 5 to 60%, respectively. In contrast, 75 km to the south in the El Faiyûm Governerate, incidence and severity were lower, 3-5 and 0.1 to <1%, respectively. Based on these figures and recent production statistics, it is estimated that malformation causes losses in Egypt of at least E35 million/year. When malformation was managed in El Giza, Ismailîa and Sharkaia by removing affected vegetative and floral terminals, the mean disease incidence and severity were lower than in non-managed orchards (69 versus 29% and 29 versus 6%, respectively). Thirty-nine isolates of the pathogen, Fusarium mangiferae, recovered during the survey were sexually incompatible with the B, C and D mating populations of the Gibberella fujikuroi complex; 10 of these were also incompatible among themselves. Four vegetative compatibility groups (VCGs) were detected among 43 of the isolates from this and a previous survey. VCG was generally not correlated with farm, governerate or host cultivar, and in three instances, isolates from two different VCGs were recovered from the same tree. RAPD analyses divided isolates into two genetically distinct clusters: Group I contained isolates in VCGs 1, 2 and 4; Group II contained isolates in VCG 3. The VCG and RAPD data support the conclusion that isolates of the pathogen from the Nile Delta were probably responsible for the recent appearance of the disease in El Faiyûm.

Relationships Among Pathogenic and Nonpathogenic Isolates ofFusarium oxysporumBased on the Partial Sequence of the Intergenic Spacer Region of the Ribosomal DNA

Using PCR, we amplified and sequenced approximately 1,000 bp of the 5' end of the intergenic spacer (IGS) of the rDNA in 15 isolates of Fusarium oxysporum and one isolate of F. subglutinans. Isolates were selected to represent diversity in our collection based on differences in pathogenic race, vegetative compatibility group (VCG), mitochondrial DNA (mtDNA) haplotype, IGS haplotype, and DNA fingerprint. The objective of this research was to clarify the origin of virulence within F. oxysporum, the relationship between pathogenic and nonpathogenic strains, and the evolution of the different races of F. oxysporum f. sp. melonis. Bootstrapped parsimony analysis of the partial IGS sequence data identified a phylogenetic tree with highly significant branches. The two F. oxysporum f. sp. melonis VCGs, 0131 and 0134, were separated into distinct lineages. Race was not distinguished by significant IGS sequence differences within the pathogen VCGs. One exception was a race 1 isolate which was associated with VCG 0131 but, based on both mtDNA and IGS haplotype, had greater affinity with VCG 0134. Two IGS sequence types were found in this race 1 isolate, one suggesting an affiliation with VCG 0131 and the other similar to isolates in VCG 0134. This may have resulted from past somatic or sexual interactions between F. oxysporum f. sp. melonis, VCGs 0131 and 0134. Nonpathogens that were vegetatively compatible with the pathogen were not closely related to the pathogen based on IGS sequence data. Thus, nonpathogens and pathogens may share common alleles at vegetative compatibility loci by coincidence rather than because of recent clonal derivation from a common ancestor.

Vegetative Compatibility, Pathogenicity, and Virulence Diversity ofFusarium oxysporumRecovered from Spinach

Fiely, M. B., Correll, J. C., and Morelock, T. E. 1995. Vegetative compatibility, pathogenicity, and virulence diversity of Fusarium oxysporum recovered from spinach. Plant Dis. 79:990-993. Four hundred thirty-nine isolates of Fusarium oxysporum recovered from symptomatic spinach seedlings and mature plants from Arkansas, California, New York, Oklahoma, South Carolina, Tennessee, and Washington in the United States as well as from Canada, Japan, and Sweden were examined for vegetative compatibility. A total of 110 isolates also were tested for pathogenicity on spinach. A minimum of 23 vegetative compatibility groups (VCGs) were identified among the 439 isolates in the collection. However, 216 (49%) of the isolates belonged to one of three vegetative compatibility groups (VCGs 1, 2, or 3). Of these 216 isolates, 125 (58%) belonged to VCG 1, 58 (27%) to VCG 2, and 33 (15%) to VCG 3. Fifty-five geographically diverse isolates from VCGs 1, 2, and 3 and 55 isolates vegetatively incompatible with VCGs 1, 2, and 3 were tested for pathogenicity on the spinach cultivar Grandstand. Of the 55 isolates in VCGs 1, 2, and 3 tested, 53 were pathogenic on spinach seedlings, while the 55 remaining isolates were not pathogenic on spinach. Among the three VCGs of Fusarium oxysporum f. sp. spinaciae identified, two distinct virulence phenotypes were detected. Isolates in VCGs 1 and 3 were significantly more virulent on the cultivar Grandstand than isolates in VCG 2. The F. o. f. sp. spinaciae population was composed of three VCGs that have a worldwide distribution, including the United States, Canada, Japan, and Sweden.

Local and Regional Variation in Populations ofFusarium oxysporumfrom Agricultural Field Soils

Populations of Fusarium oxysporum were sampled from two agricultural fields in Maryland. Among 197 isolates, 56 vegetative compatibility groups (VCGs) and 25 mitochondrial DNA (mtDNA) haplotypes were identified. Fifty-four VCGs, representing 97% of the VCG diversity and 92% of the mtDNA haplotypes, were found among 78 isolates that were not pathogenic to muskmelon. The remaining two VCGs included 115 isolates of F. o. melonis: 40 isolates in VCG 0131 (races 0, 1, and 2) and 75 in 0134 (races 1 and 1,2). This is the first report from North America of race 1,2, for which there is presently no resistance in muskmelon. The two VCGs associated with virulent isolates also included four nonpathogenic isolates [...]