Aflatoxins are carcinogenic mycotoxins most frequently associated with the filamentous fungus, Aspergillus flavus. These potent toxins pose serious health threats and their concentrations in foods are widely regulated. Maize, a critical staple of billions, is frequently contaminated with aflatoxins. Development of commercial maize hybrids with superior resistance to aflatoxin contamination has been sought for over 30 years without success. Analyses of native maize land races (MLRs) from Mexico revealed several accessions with significant resistance to both aflatoxin contamination and fungal reproduction. Physical barriers are important components of MLRs resistance. Traditional use of MLRs may reduce human exposure to aflatoxins. MLRs may contribute resistant genes of significant value in breeding for aflatoxin resistance. In Mexico, maize is produced from<10 to over 2,000 masl. Elevation had only minor influence on community compositions of aflatoxin-producing fungi associated with maize over three years in Sonora, Mexico. Most variation in community structure occurred between years. Dominant vegetative compatibility groups (VCGs) differed among years but were detected in similar frequencies across four agroecological zones. Multiple locations and multiple years must be sampled to obtain realistic assessments of the most successful VCGs. Elevated frequencies of VCG YV150 throughout Sonora during 2006 led to investigate genetic diversity within this VCG using microsatellite loci. The 2006 increases were attributed to rapid increase of a single clone. Examination of YV150 isolates collected over 20 years in the US and Mexico revealed several haplotypes and two genetically distinct populations, which were composed of isolates containing only a population specific mating-type idiomorph. Microsatellite loci in each population were in gametic equilibrium. Gene flow between isolates with different idiomorphs was not detected. VCG YV36, to which the biocontrol agent AF36 belongs, was found to be endemic to Mexico. Microsatellite loci revealed diversity within YV36 from Mexico, but all isolates harbored the single nucleotide polymorphism in the aflatoxin polyketide synthase gene, pksA, that confers atoxigenicity to AF36. Three YV36 isolates also had deletions in pksA suggesting continued degradation. Presence of endemic YV36 isolates in Mexico may facilitate rapid regulatory approval of AF36 for use in prevention of aflatoxin contamination of maize in Mexico.

A rubelose é uma doença que atinge galhos e ramos, e é causada pelo fungo Erythricium salmonicolor, o qual infecta várias espécies vegetais, tais como citros, seringueira, e macieira. Esta doença vem chamando a atenção dos citricultores devido à redução de até 10% da produção de citros, a qual é preocupante para o Brasil, o maior produtor de laranja do mundo. Entretanto, a diversidade do fungo E. salmonicolor em cultivares brasileiras ainda não foi avaliada. Desta maneira, este trabalho teve como objetivos: i) avaliar a variabilidade genética, por meio de RAPD, de isolados do fungo E. salmonicolor provenientes de diferentes regiões citrícolas de São Paulo e Minas Gerais, ii) avaliar a compatibilidade vegetativa e fusão de hifas deste fungo e iii) selecionar bactérias endofíticas com potencial para o controle deste fungo fitopatogênico. Após a análise por RAPD, foram observados 6 grupos distintos (A, B, C, D, E, F), os quais não apresentaram correlação com o local de origem e espécie hospedeira. No teste de compatibilidade vegetativa houve encontro de hifas em todos os cruzamentos e 84% destes apresentaram fusão entre as hifas. Foi verificada compatibilidade entre linhagens, embora não tenha sido observada correlação com os haplótipos. No teste de antagonismo, 8 isolados bacterianos inibiram E. salmonicolor. Entretanto, foi observada diferença na interação entre as bactérias e diferentes isolados de E. salmonicolor, visto que bactérias diferentes inibiram os dois genótipos do fungo, revelando a variabilidade genética entre estas linhagens que pertencem a diferentes haplótipos. Os resultados observados neste trabalho indicam a importância de futuros estudos sobre a fase sexual de E. salmonicolor, uma vez que a anastomose de hifas precede a formação de heterocário, responsável pelos processos de recombinações sexuais e parassexuais, que geram variabilidade genética em fungos filamentosos. / The fungus Erythricium salmonicolor is the causal agent of pink disease, which infects branches of many host plants, such as citrus, rubber, and apple. This disease may be a serious problem in Brazil, since it can reduce the citrus production up to 10%. Brazil is the major world citrus producer, therefore this problem is alarming. The genetic diversity of E. salmonicolor from Brazilian plants has not been evaluated, so the aims of this study were i) to evaluate the genetic diversity by RAPD of E. salmonicolor isolates from São Paulo and Minas Gerais; ii) to evaluate the vegetative compatibility and hyphal fusion of this fungus; and iii) to select endophytic bacteria able to inhibit the E. salmonicolor growth. RAPD analysis showed at least 6 distinct haplotypes (A, B, C, D, E, F), which did not have correlation with the isolation site and host plant. Also, vegetative compatibility tests showed that 84% of crosses resulted in hyphal fusion, but this compatibility was not related to the RAPD haplotypes. Eight endophytic bacteria were selected against E. salmonicolor, which could be used for biological control of this pathogen. However it was observed different types of interaction among endophytic bacteria and E. salmonicolor strains, since these bacteria inihibited differentially two fungi isolates. It reveals the genetic variability between these fungi isolates that belongs to different haplotypes These results show the importance of future studies concerning the sexual phase of E. salmonicolor, since the genetic variability seems to be high and this hyphal fusion, which precede the formation of heterokaryon (sexual and parassexual reproduction), could be responsible for the variability in this filamentous fungus.

A rubelose é uma doença que atinge galhos e ramos, e é causada pelo fungo Erythricium salmonicolor, o qual infecta várias espécies vegetais, tais como citros, seringueira, e macieira. Esta doença vem chamando a atenção dos citricultores devido à redução de até 10% da produção de citros, a qual é preocupante para o Brasil, o maior produtor de laranja do mundo. Entretanto, a diversidade do fungo E. salmonicolor em cultivares brasileiras ainda não foi avaliada. Desta maneira, este trabalho teve como objetivos: i) avaliar a variabilidade genética, por meio de RAPD, de isolados do fungo E. salmonicolor provenientes de diferentes regiões citrícolas de São Paulo e Minas Gerais, ii) avaliar a compatibilidade vegetativa e fusão de hifas deste fungo e iii) selecionar bactérias endofíticas com potencial para o controle deste fungo fitopatogênico. Após a análise por RAPD, foram observados 6 grupos distintos (A, B, C, D, E, F), os quais não apresentaram correlação com o local de origem e espécie hospedeira. No teste de compatibilidade vegetativa houve encontro de hifas em todos os cruzamentos e 84% destes apresentaram fusão entre as hifas. Foi verificada compatibilidade entre linhagens, embora não tenha sido observada correlação com os haplótipos. No teste de antagonismo, 8 isolados bacterianos inibiram E. salmonicolor. Entretanto, foi observada diferença na interação entre as bactérias e diferentes isolados de E. salmonicolor, visto que bactérias diferentes inibiram os dois genótipos do fungo, revelando a variabilidade genética entre estas linhagens que pertencem a diferentes haplótipos. Os resultados observados neste trabalho indicam a importância de futuros estudos sobre a fase sexual de E. salmonicolor, uma vez que a anastomose de hifas precede a formação de heterocário, responsável pelos processos de recombinações sexuais e parassexuais, que geram variabilidade genética em fungos filamentosos. / The fungus Erythricium salmonicolor is the causal agent of pink disease, which infects branches of many host plants, such as citrus, rubber, and apple. This disease may be a serious problem in Brazil, since it can reduce the citrus production up to 10%. Brazil is the major world citrus producer, therefore this problem is alarming. The genetic diversity of E. salmonicolor from Brazilian plants has not been evaluated, so the aims of this study were i) to evaluate the genetic diversity by RAPD of E. salmonicolor isolates from São Paulo and Minas Gerais; ii) to evaluate the vegetative compatibility and hyphal fusion of this fungus; and iii) to select endophytic bacteria able to inhibit the E. salmonicolor growth. RAPD analysis showed at least 6 distinct haplotypes (A, B, C, D, E, F), which did not have correlation with the isolation site and host plant. Also, vegetative compatibility tests showed that 84% of crosses resulted in hyphal fusion, but this compatibility was not related to the RAPD haplotypes. Eight endophytic bacteria were selected against E. salmonicolor, which could be used for biological control of this pathogen. However it was observed different types of interaction among endophytic bacteria and E. salmonicolor strains, since these bacteria inihibited differentially two fungi isolates. It reveals the genetic variability between these fungi isolates that belongs to different haplotypes These results show the importance of future studies concerning the sexual phase of E. salmonicolor, since the genetic variability seems to be high and this hyphal fusion, which precede the formation of heterokaryon (sexual and parassexual reproduction), could be responsible for the variability in this filamentous fungus.