| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. (INIFAP), Campo Experimental del Bajío, Celaya, Guanajuato, Mexico
María-Teresa Ramírez-Rueda
Department of Plant Genetic Engineering, CINVESTAV, Unidad Irapuato, Apdo. Postal 629, C.P. 36500, Irapuato, Guanajuato, Mexico
Mariandrea Cabral-Enciso
Unidad Académica de Agronomía, Universidad Autónoma de Zacatecas, Zacatecas, Mexico
Mónica García-Serrano
Department of Genetic Engineering, CINVESTAV, Unidad Irapuato, Apdo. Postal 629, C.P. 36500, Irapuato, Guanajuato, Mexico
Zoraida Lira-Maldonado
Ramón Gerardo Guevara-González
Instituto Tecnológico de Celaya, Deptamento de Bioquímica, Avenida Tecnológico Esquina con García Cubas, Sin Número, Celaya, Guanajuato, Mexico
Mario González-Chavira
Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. (INIFAP), Campo Experimental del Bajío, Celaya, Guanajuato, Mexico
June Simpson 1
Department of Plant Genetic Engineering, CINVESTAV, Unidad Irapuato, Apdo. Postal 629, C.P. 36500, Irapuato, Guanajuato, Mexico
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Although several reports have described the occurrence of the teleomorphic state of Glomerella lindemuthiana (anamorph, Colletotrichum lindemuthianum), there has been a lack of continuity in this research. To identify G. lindemuthiana isolates capable of developing the teleomorphic state, 19 Mexican isolates were analyzed. Three types of response were observed: (i) negative, where only mycelial growth with or without acervuli was observed; (ii) potential, where in addition to the above, spherical perithecia-like structures were observed; (iii) positive, where perithecia containing asci and ascospores were observed. All strains were self-sterile and only one combination of strains produced fertile perithecia. From this fertile combination 168 individual ascospore cultures were isolated, including five from a single ascus. Forty-four monoascospore cultures were characterized with AFLP, confirming that these individuals were progeny from a sexual cross between the original two G. lindemuthiana isolates and that sexual reproduction in G. lindemuthiana is heterothallic in nature. Analysis of the parental strains with degenerate PCR primers indicated that sequences homologous to the HMG box of the MAT1-2 idiomorph are present in both parental isolates. This supports previous observations in other Glomerella species where the standard ascomycete configuration of distinct idiomorphs at the MAT locus does not hold true. The significance of these results is discussed.
Key words: AFLP, Ascomycete, Colletotrichum lindemuthianum, HMG, MAT1-2
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
). Diversity of G. lindemuthiana based on molecular markers and pathotypes also has been studied to some extent (Fabre et al 1995, Balardin et al 1997, Sicard et al 1997, González et al 1998, González 1999). However, although G. lindemuthiana meets most of the criteria for a model organism (culturability, transformability, short life cycle, simple inoculation procedure etc.), it lacks a well characterized sexual reproduction cycle.
This means that the role which sexual reproduction plays in diversity and the production of new pathotypes cannot be assessed and other interesting phenomena such as genome organization, the genetic basis of pathogenicity, mating type and vegetative compatibility, cannot be directly addressed. The development of classical genetic analysis based on the segregating population of a sexual cross would open the possibility of genetic mapping and the cloning and characterization of genes of interest as has been done for other pathogenic fungi (Xu and Leslie 1996, Pongam et al 1998, Zhong et al 2002).
Although the occurrence of a sexual cycle in G. lindemuthiana in laboratory cultures was described first in 1913 (Shear and Wood 1913), investigation in this field has advanced sporadically since then and many aspects of the mechanism of sexual reproduction in this fungus remain unclear.
The genus Glomerella is unusual because some individual species such as Glomerella cingulata and Glomerella graminicola are both heterothallic and homothallic (Wheeler 1956, Vaillancourt and Hanau 1991), whereas G. musae has been reported as heterothallic (Rodríguez and Owen 1992). G. lindemuthiana was described first as homothallic (Shear and Wood 1913) although later studies (Batista and Chaves 1982, Bryson 1990) reported heterothallism. These studies reported that fertile perithecia were produced only when two distinct isolates were crossed and identified recombinant phenotypes in the segregating populations; however, only a small number of genetic markers and relatively small segregating populations were analyzed in these studies.
The genetic basis of sexual compatibility in Glomerella also is unclear because fertile interactions are not consistent with the single locus/two idiomorph system described for other ascomycetes where the mating types are distinguished by a single locus containing different genetic information (MAT1-1 and MAT1-2 idiomorphs, Turgeon and Yoder 2000) in each parent (Kronstad and Staben 1997). The mating types of the parental strains of diverse ascomycetes such as Neurospora, Podospora and Magnaporthe often can be determined by the presence or absence of the MAT1-2 idiomorph. However in the genus Glomerella it has been suggested that a single locus with multiple alleles controls mating in G. cingulata (Cisar and te Beest 1999), whereas two unlinked loci control mating in G. graminicola (Vaillancourt et al 2000).
All previous reports agree that sexual reproduction in G. lindemuthiana is rare and occurs only between a few compatible isolates that produce a few fertile perithecia containing asci and ascospores. No reports exist of the occurrence of sexual reproduction in G. lindemuthiana under field conditions.
Phenotypic characteristics, pathotypes or mutations previously were used to study the progeny of genetic crosses and, although Bryson employed RFLP molecular markers, her results were inconclusive (Bryson 1990). With the development of simple multilocus markers such as AFLPs it should be possible to efficiently study the progeny of putative sexual crosses between distinct G. lindemuthiana isolates while avoiding the inconsistencies associated with the analysis of morphological characteristics.
Our objective was to identify sexually compatible G. lindemuthiana isolates from a collection of Mexican isolates, demonstrate with AFLP markers that progeny obtained from single ascospore cultures were the product of a heterothallic mating between two unrelated isolates and characterize the mating-types of the parental isolates using degenerate oligonucleotide primers designed to amplify the HMG motif of the MAT1-2 idiomorph of pyrenomycetes (Arie et al 1997).
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
) had been characterized in terms of pathotype and genotype (González 1999, González et al 1998) and three new isolates (17–19, TABLE I) also were included.
|
) (8 g glucose, 0.6 g Ca(NO3)0.4H2O, 1 g KH2PO4, 0.5 g MgSO40.7H2O, 20 g agar/L, pH 5) at 20 C.
Pathogenicity tests.— –
The pathotypes of the three new isolates, MU 01, MU 02 and MU 03, were determined and the pathotype of the parental strain DGO 02 also was confirmed in this work with a set of 12 P. vulgaris differential cultivars (Michelite, Michigan Dark Red Kidney, Perry Marrow, Cornell 49242, Widusa, Kaboon, Mexico 222, PI 207262, To, Tu, AB 136, G2333) and binary nomenclature as described by Pastor-Corrales (1991). In addition cultivars La Victoire and Flor de Mayo Bajío also were inoculated. Pathotypes of all other isolates had been determined by González et al (1998).
Isolates were grown on cornmeal agar as above at 22 C to induce abundant sporulation. Spores were harvested and a suspension of 1.5 x 106 conidia/mL was produced. Two drops of Tween 20 were added to each 100 mL of the conidial suspension. Four plants of each of the 12 differential cultivars were inoculated 10 d after emergence by spraying the conidial suspension on the underside of the primary leaves. The experiment was repeated at least twice (at least eight plants of each cultivar were analyzed for each isolate). Inoculated plants were incubated at around 95% humidity, 22 C and a photoperiod of 12 h light/dark for 3 d and thereafter under conditions of normal humidity with the same temperature and photoperiod. Ten d after inoculation, symptoms were evaluated with a five-point scale (Garrido-Ramirez and Romero-Cova 1989). Reactions were classified as: 0, no visible symptoms; 1, small lesions on major veins visible only on the underside of the leaf; 2, lesions visible on both the top and underside of the leaf; 3, defoliation of plant and sporulation of fungus; 4, plant death. Reactions classified as 0–2 were considered resistant whereas 3 and 4 were considered susceptible.
Tests for sexual compatibility.— –
Disks of Whatman No. 1 filter paper were placed on Petri dishes containing solidified KG medium. Isolates were tested for the ability to undergo sexual reproduction by themselves and in pairs, 100 µL of a 104 conidia/mL suspension of each isolate were inoculated at the same spot on the center of the filter paper. Petri dishes were incubated in the dark (an essential requirement for development of reproductive structures in this fungus; Kimati and Galli 1970, Bryson 1990) for 6 wk at 20 C. The presence of structures indicating the occurrence of sexual reproduction was evaluated by observation of the cultures under a Carl Zeiss stereoscopic microscope.
Isolation of monoascospore cultures.— – Individual perithecia or masses of spherical structures with rigid walls were isolated from the Petri dishes, suspended in sterile water and placed on a microscope slide where they were broken open carefully with a cover slip under a stereoscopic microscope. Water containing ascospores liberated from these structures was transferred to acidified PDA medium and carefully dispersed with a glass rod to separate individual ascospores. After 24–48 h germinated ascospores were identified under a light microscope and transferred to fresh acidified PDA with an entomological needle on the end of a dissecting needle. In the case of the isolation of ascospores from individual asci, the asci first were isolated under a light microscope with a fine hair attached to a dissecting needle and transferred to acidified PDA medium. Using the same hair the ascospores were gently liberated from the asci and distributed over the PDA medium. Germinated ascospores were transferred to fresh acidified PDA medium as above. Monoascospore cultures were preserved at 4 C in acidified PDA overlaid with mineral oil.
AFLP analysis of monoascospore cultures and parental strains.— –
DNA was obtained from monoascospore cultures and parental strains and subjected to AFLP analysis as described by González et al (1998). Oligonucleotide primers used for the pre-amplification step were:
EcoRI (EcoRI+A) 5'-AGACTGCGTACCAATTC/A-3',
MseI (MseI+A) 5'-GACGATGAGTCCTGAGTAA/A-3'
The pre-amplification step was followed by a second selective amplification step with two selective nucleotides. An extra T residue was added to the EcoRI primer whereas a C residue was added to the Mse I primer. Segregation of polymorphic bands was analyzed with the Chi2 test.
Characterization of mating types of parental strains.— –
Degenerate oligonucleotide primers (NcHMG1 [5'-CCYCGYCCY CCYAAYGCNTAYAT-3'] and NcHMG2 [5'-CGNGGRTTRTARCGRTARTNRGG-3']), designed to amplify the HMG motif of the MATa idiomorph of Neurospora crassa and other pyrenomycetes (Arie et al 1997), were used to determine whether sequences homologous to the HMG motif were present in the G. lindemuthiana parental strains DGO 02 and MU 03. The PCR reactions were carried out as described in Arie et al (1997), and the products were viewed under UV light after electrophoresis in a 2% agarose gel. DNA from N. crassa MATa (MAT1-2) and MATA (MAT1-1) strains was used as control.
Amplified fragments for DGO 02 and N. crassa MATa strains were cloned into the vector pCR 2.1 TOPO (Invitrogen, California.) following the manufacturers instructions and sequenced on an ABI 3700 sequencer. Based on the sequence obtained for DGO 02, specific primers were designed (indicated in bold in FIG. 4) and used to amplify the MAT1-2 region in DGO 02, MU 03 and the N. crassa MATa strain. The amplified fragments were sequenced as described above and compared to the G. graminicola HMG box sequence (AF204961
[GenBank]
), obtained from Vaillancourt et al (2000) and the G. cingulata sequence accessed as AY357890
[GenBank]
from GenBank. DNA and protein sequence analysis was carried out with NCBI BLAST and the DNAstar/Clustal W editing and alignment programs.
|
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
) were crossed in all possible pairwise combinations as described in Materials and Methods or were grown individually under the same conditions. In total 190 distinct crosses were tested and all combinations were duplicated. From these experiments three main classes of interaction were determined: class i, negative, no perithecia-like structures were observed; class ii, potential, isolated or clumped spherical structures with a rigid wall, denominated protoperithecia were observed (FIG. 1A); class iii, positive, perithecia, asci and ascospores were observed (FIG. 1B, C). In class iii interactions the majority of structures observed were class ii or protoperithecia with the sporadic occurrence of mature perithecia (TABLE II). In all classes both the presence or absence of acervuli were observed in at least one of the replicate experiments.
|
|
). In the first experiment combining isolates DGO 02 vs. MU 03, involving two replicates a large number of protoperithecia were observed but only one perithecium containing asci and ascospores. On repetition of this combination with a greater number of replicates, again many protoperithecia were observed but it also was possible to detect up to six perithecia producing ascospores per Petri dish.
Analysis of progeny.— –
From this fertile combination 168 monoascospore cultures were obtained. Attempts to isolate and analyze the eight ascospores from a single ascus were unsuccessful due to the different stages of development of the spores and difficulty in separation of individual asci (FIG. 1D). In the few cases where this was possible, not all eight ascospores germinated on PDA. A maximum of five ascospores were isolated from a single ascus.
Visible analysis of a selection of 16 monoascospore cultures of the progeny from the interaction between DGO 02 and MU 03 showed a wide variation in morphology including speed of sporulation and the production of melanized mycelia (data not shown).
DGO 02 and MU 03 also were used as tester strains in crosses with an additional seven isolates to identify other strains capable of completing a sexual reproductive cycle. These experiments were carried out as described in Materials and Methods, and a new combination capable of producing fertile perithecia, asci and ascospores (MU 03 and JAL 05) was identified (data not shown).
AFLP patterns for the parental strains DGO 02 and MU 05 and 44 progeny obtained from monoascospore cultures, including the five monoascospore cultures obtained from a single ascus were determined. Eighty-one AFLP bands ranging in size from 50 to 700 bps were identified in the parental isolates and of these 23 (28.4%) were polymorphic between the parents. All progeny samples showed molecular fingerprints distinct to the parental patterns but composed of bands from each of the parents as would be expected in a sexually segregating population (FIG. 2). Two pairs of isolates showed identical fingerprints including one pair from the samples obtained from a single ascus. This would be expected due to the formation of "twins" by mitotic division of the haploid cells following meiosis. Statistical analysis of the segregation of the AFLP markers by the 
2 test supported a ratio of 1:1 (TABLE III) in agreement with the segregation of haploid individuals following sexual recombination and meiosis.
|
|
). This is a strong indication that sequences homologous to the MAT1-2, HMG motif are present in both the G. lindemuthiana parental strains but as expected only in the N. crassa MATa strain.
|
) and MATa sequences showed strong homology to other fungal MAT1-2 sequences in the database.
Oligonucleotide primers specific for the DGO 02 sequence (FIG. 4) were designed and used to amplify genomic DNA from the DGO 02, MU 03 and N. crassa MATa and MATA strains as described above. These specific primers produced fragments of around 200 bp in the DGO 02 and MU 03 strains but no amplified fragments were obtained from either N. crassa strain (data not shown) indicating that these primers are specific for G. lindemuthiana. The amplified fragments obtained for strains DGO 02 and MU 03 using the specific primers were sequenced and found to be identical.
Comparison of the MAT1-2 sequence from DG0 02/MU 03 at both the DNA and protein level showed a high level of similarity to MAT1-2 sequences from related Glomerella species (G. graminicola accession numbers AF204960
[GenBank]
, AF204961
[GenBank]
and Glomerella cingulata accession number AY357890
[GenBank]
) (FIG. 4) but a lower level of similarity to the MATa sequence of N. crassa (data not shown).
The G. lindemuthiana MAT1-2 sequences reported here (FIG. 4) have been deposited in GenBank and assigned the accession numbers AY724682
[GenBank]
(DGO 02) and AY724683
[GenBank]
(MU 03).
Determination of pathotypes.— –
Pathotypes of the parental isolates were determined with a set of 12 differential cultivars as described in Materials and Methods. Isolate DGO 02 was characterized as pathotype 1088, infecting cultivars Mexico 222 and AB136, whereas isolate MU 03 was characterized as pathotype 1280, which infects cultivars To and AB136 (TABLE I). MU 01 and MU 02 were identified respectively as pathotypes 2 and 9. In addition cultivars La Victoire and Flor de Mayo Bajío were inoculated with both isolates and found to be susceptible (data not shown).
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
, 1992) where the majority of isolates are interfertile and both homothallic and heterothallic strains are found.
Although only two combinations of isolates produced fertile perithecia it is possible that the other isolates that produced protoperithecia may be capable of producing mature perithecia but at a very low frequency. This is supported by the observation that a greater number of mature perithecia were observed as the number of replicate experiments analyzed increased and that more than one common isolate was involved in different interactions where protoperithecia were observed. These results agree with Kimati and Galli (1970), Batista and Chaves (1982) and Bryson (1990) where the sporadic formation of mature perithecia at a low frequency also was observed. Ongoing analysis involving crosses between each of the segregating individuals and each parental strain has not uncovered individuals showing either homothallic mating or increased fertility. The capacity for fertile sexual interactions also seems to be independent of vegetative compatibility because the parental strains DGO 02 and MU 03 have been shown to be incapable of undergoing successful hyphal anastomosis (Rodríguez et al 2004).
The results of this study are in agreement with a heterothallic interaction because none of the original 19 isolates tested when grown alone were capable of producing either protoperithecia or mature perithecia. Visual analysis of the morphology of the monoascospore progeny and comparison with the parental strains showed a range of different rates of colony growth and sporulation as would be expected in a segregating population and are similar to the results of Bryson (1990) who made a detailed study of colony growth and morphology in the progeny of a cross of G. lindemuthiana isolates.
The possibility of using molecular markers for analysis of segregating populations has been demonstrated (Kema et al 1996, Murtagh et al 2000). AFLP analysis of G. lindemuthiana allowed a large number of polymorphic markers to be analyzed simultaneously in comparison to the morphological and RFLP/isozyme markers employed in previous studies (Bryson 1990, Lenne and Burdon 1990, Bonde et al 1991, Sherriff et al 1994). The AFLP analysis confirmed that the progeny were obtained from a sexual cross both visually in the banding patterns and in the 1:1 segregation ratios obtained. All segregating progeny tested showed recombinant genotypes that were combinations of the parental genotypes. A preliminary analysis of the pathotypes of individual isolates of the segregating population also has identified recombinant phenotypes (data not shown). For the first time progeny of a single ascus were analyzed and showed to present four distinct genotypes and the occurrence of twins. From these results we conclude that the segregation patterns were due to heterothallic mating during a sexual cross.
The mechanism governing sexual compatibility in G. lindemuthiana is unknown. Analysis of the parental strains in this study with the specific oligonucleotide primers indicates that sequences homologous to the HMG box of the MAT1-2 idiomorph found in other ascomycetes are present in both parental isolates. It therefore was not possible to characterize DGO 02 and MU 03 as MAT1-1 or MAT1-2 strains and suggests that mating type in these G. lindemuthiana isolates is not directly determined by the MAT1 locus. Further analysis of the 19 isolates (TABLE I) showed that all produced an amplified fragment of around 200 bp using the specific oligonucleotide primers, as did all 12 members of the segregating population that were tested (data not shown).
Similar results have been observed for G. graminicola (Vaillancourt et al 2000, Chen et al 2002) where cross fertility between heterothallic isolates appears to be regulated by two unlinked loci (Vaillancourt et al 2000). In G. cingulata (anamorph, Colletotrichum gloeosporioides) however a single locus with multiple alleles has been suggested as being responsible for the determination of mating type (Cisar and te Beest 1999). Taken together these data confirm that determination of mating type in the genus Glomerella is complex and distinct from the bimodal system reported for most other filamentous ascomycetes (Arie et al 1997, Turgeon and Yoder 2000).
Comparison at the sequence level between three species of the genus Glomerella for the MAT1-2 HMG region indicates a high level of sequence conservation among isolates from different species of Glomerella and among isolates obtained from distant regions (G. lindemuthiana and G. graminicola in America and G. cingulata in Australasia).
A phylogenetic analysis of the sequences indicates that G. lindemuthiana and G. cingulata are more closely related to each other than to the G. graminicola isolate (data not shown). These results also are reflected in the homology observed between the derived amino-acid sequences. This agrees with the accepted taxonomic classification of these three species (Sutton 1992).
This study opens the door for detailed genetic analysis of G. lindemuthiana. Because the parental strains show different pathotypes it should be possible to determine the patterns of inheritance of the corresponding avirulence genes. Other characteristics that could be studied at the genetic level are mating type and genes controlling vegetative compatibility, neither of which have been studied extensively in G. lindemuthiana. The construction of a genetic map of G. lindemuthiana based on molecular markers would allow markers associated with the traits mentioned above to be identified, leading to the comparison of inheritance of these traits across isolates and eventually to the isolation and characterization of the genes responsible. A molecular marker map also would provide information on the size and chromosome number of the G. lindemuthiana genome.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
1 Corresponding author. E-mail: jsimpson{at}ira.cinvestav.mx
|
LITERATURE CITED |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Balardin RS, Jarosz AM, Kelly JD. 1997. Virulence and molecular diversity in Colletotrichum lindemuthianum from South, Central, and North America. Phytopathology 87:1184–1191.[Medline]
Batista UG, Chaves GM. 1982. Patogenicidad de culturas monoascosporicas de cruzamento entre racas de Colletotrichum lindemuthianum (Sacc. et Magn.) Scrib Fitopatologia Brasileira 7:285–293.
Bonde MR, Peterson GL, Maas JL. 1991. Isozyme comparisons for identification of Colletotrichum species of strawberry. Phytopathology 81:1523–1528.[CrossRef]
Bryson RJ. 1990. Sexual hybridization and the genetics of pathogenic specificity in Colletotrichum lindemuthianum. [Doctoral dissertation]. University of Birmingham. 272 p
Chen F, Goodwin PH, Khan A, Hsiang T. 2002. Population structure and mating-type genes of Colletotrichum graminicola from Agrostis palustris. Can J Micro 48:427–436.
Cisar CR, te Beest DO. 1999. Mating system of the filamentous ascomycete, Glomerella cingulata. Curr Genet 35:127–133.[CrossRef][Medline]
Fabre JV, Julien J, Parisot D, Dron M. 1995. Analysis of diverse isolates of Colletotrichum lindemuthianum infecting common bean using molecular markers. Mycol Res 99:429–435.
Garrido-Ramírez ER, Romero-Cova S. 1989. Identificación de razas de Colletotrichum lindemuthianum (Sacc. Y Magn.) Scrib. en México y búsqueda de resistencia genética a este hongo. Agrociencia 77:139–156.
González MM. 1999. Caracterización de aislados mexicanos de Colletotrichum lindemuthianum usando marcadores moleculares de ADN y variedades diferenciales y búsqueda de resistencia en variedades mexicanas. [Doctoral dissertation]. Irapuato, Mexico. Centro de Investigación y de Estudios Avanzados del I.P.N. 105 p
———, Rodríguez R, Zavala ME, Jacobo JL, Hernández F, Acosta J, Martínez O, Simpson J. 1998. Characterization of Mexican isolates of Colletotrichum lindemuthianum by using differential cultivars and molecular markers. Phytopathology 88:292–299.[Medline]
Kema GHJ, Verstappen ECP, Todorova M, Waalwijk C. 1996. Successful crosses and molecular tetrad and progeny analysis demonstrate heterothallism in Mycosphaerella graminicola. Curr Genet 30:251–258.[CrossRef][Medline]
Kimati H, Galli F. 1970. Glomerella cingulata f.sp. phaseoli, fase ascogena do agente causal da anthracnose do feijoeiro. Anais da Escola Superior de Agricultura "Luiz de Queiroz" 27:411–437.
Kronstad JW, Staben C. 1997. Mating type in filamentous fungi. Ann Rev Genet 31:245–276.[CrossRef][Medline]
Lenne JM, Burdon JJ. 1990. Preliminary study of virulence and isozymic variation in natural populations of Colletotrichum gloeosporioides from Stylosantes guianensis. Phytopathology 80:728–731.[CrossRef]
Murtagh GJ, Dyer PS, Crittenden PD. 2000. Sex and the single lichen. Nature 404:564.[CrossRef][Medline]
Pastor-Corrales MA. 1991 Estandarización de variedades diferenciales y designación de razas de Colletotrichum lindemuthianum (abstract). Phytopathology 81:694.
Perfect SE, Hughes HB, O’Connell RJ, Green JR. 1999. Colletotrichum: a model genus for studies on pathology and fungal plant interactions. Fungal Genet Biol 27:186–198.[CrossRef][Medline]
Pongam P, Osborn TC, Williams PH. 1998. Genetic analysis and identification of amplified fragment length polymorphism markers linked to the alm1 avirulence gene of Leptosphaeria maculans. Phytopathology 88:1068–1072.[Medline]
Rodríguez R, Owen JL. 1992. Isolation of Glomerella musae (Teleomorph of Colletotrichum musae [Berk. & Curt.] Arx) and segregation of ascospore progeny. Mycol Res 16:291–301.
Rodríguez-Guerra R, Ramírez-Rueda M-T, Simpson J. 2004. Capacidad de anastomosis en una colección de cepas del hongo Colletotrichum lindemuthianum (Sacc. et Magn.) Scrib., agente causal de la antracnosis del frijol (Phaseolus vulgaris L.). Revista Mexicana de Fitopatología 22:37–43.
Shear CL, Wood AK. 1913. Studies of fungal parasites belonging to the genus Glomerella. USDA Bureau of Plant Industry 252:1–110.
Sherriff C, Whelan MJ, Arnold GM, Bailey JA. 1994. Ribosomal DNA sequence analysis reveals new species groupings in the genus Colletotrichum. Exp Mycol 18:121–138.[CrossRef]
Sicard D, Michalakis Y, Dron M, Neema C. 1997. Genetic diversity and pathogenic variation of Colletotrichum lindemuthianum in three centers of diversity of its host, Phaseolus vulgaris. Phytopathology 87:807–813.[Medline]
Sutton BC. 1992. The genus Glomerella and its anamorph Colletotrichum. In: Bailey JA, Jeger MJ, eds. Colletotrichum: biology, pathology and control. Wallingford, U.K.: C.A.B. International. p 1–26.
Turgeon BG, Yoder OC. 2000. Proposed nomenclature for mating type genes of filamentous ascomycetes. Fungal Genet Biol 31:1–5.[CrossRef][Medline]
Vaillancourt LJ, Hanau RM. 1991. A method for analysis of Glomerella graminicola from maize. Phytopathology 81:530–534.[CrossRef]
———, ———. 1992. Genetic and morphological comparisons of Glomerella (Colletotrichum) isolates from maize and from sorghum. Exp Mycol 16:219–229.
———, Du M, Wang J, Rollins J, Hanau R. 2000. Genetic analysis of cross fertility between two self-sterile strains of Glomerella graminicola. Mycologia 92:430–435.[CrossRef]
Wheeler HE. 1956. Genetics and evolution of heterothallism in Glomerella. Phytopathology 44:342–345.
Xu J, Leslie JF. 1996. A genetic map of Giberella fujikuroi mating population A (Fusarium moniliforme). Genetics 143:175–189.[Abstract]
Zhong S, Steffenson B J, Martínez JP, Ciuffetti LM. 2002. A molecular genetic map and electrophoretic karyotype of plant pathogenic fungus Cochliobolus sativus. Mol Plant Mic Int 15:481–492.[CrossRef]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
