Controle da ferrugem do cafeeiro (Hemileia vastatrix) com Bacillus subtilis: folhas destacadas e mudas.

O efeito dos isolados AP-3 e AP-150 de B. subtilis aplicados em suspensoes autoclavadas ou nao, foi avaliado sobre folhas destacadas e mudas de cafeeiro da variedade caturra, no controle da ferrugem. As pulverizacoes das suspensoes de B. subtilis foram realizadas 72 horas antes da inoculacao do patogeno, ambas com auxilio de pistola acoplada a bomba de vacuo, sobre a superficie inferior das folhas. Apos inoculacao do patogeno as folhas e mudas permaneceram em camara umida e escura a +- 24 C. Trancorrido deste periodo, a incubacao das folhas foi a +- 25 C com fotoperiodo de 12 horas, enquanto das mudas em casa de vegetacao a +- 25 C. Mesmo utilizando uma variedade extremamente susceptivel e uma raca de H. vastatrix altamente agressiva foi verificado, tanto emfolhas destacadas quanto em mudas, que B. subtilis controlou a ferrugem quando avaliado o numero de lesoes/folha. Para os dois isolados do antagonista a suspensao nao autoclavada foi mais eficiente que a autoclavada. Outro fato interessante e que os tratamentos com suspensao nao autoclavados de B. subtilis apresentavam periodo latente superior aos demais tratamentos. Os dois isolados de B. subtilis apresentaram comportamento semelhante

Efeito de Bacillus subtilis sobre a germinação de urediniosporos de cinco raças de Hemileia vastatrix.

Para verificar o efeito antagonico dos isolados de B. subtilis sobre a germinacao de cinco racas de H. vastatrix (II, I, XXV, XXXI e XXIX, portadores dos genes V5, V2V5, V2V5V6, V2V5V6V9 e V5V6V7V8V9 de virulencia, respectivamente), foi realizado ensaio colocando-se gotas contendo suspensoes de celulas dos isolados AP-3 e AP-150 nas concentracoes de 2,15 x 10 8 e 2,9 x 10 8 celulas/ml, sobre laminas de vidro, sendo a seguir adicionados urediniosporos de H. vastatrix das cinco racas. Apos seis horas de umidade relativa de 100% e escuro foi efetuado a avaliacao contando-se os urediniosporos germinados. O experimento foi repetido nas concentracoes de 5,4 x 10 8, 5,4 x 10 7, 5,4 x 10 6 celulas/ml para dois antagonistas. AP-3 e AP-150 nas concentracoes de 2 ou5 x 10 8 celulas/ml, inibiram totalmente a germinacao dos urenidiosporos das cinco racas de H. vastratix, mostrando que nao possui especificidade. Na diluicao 5,4 x 10 7 celulas/ml ambos os isolados inibiram mais que 96% a germinacao dos urenidiosporos, enquanto que na diluicao 5,4 x 10 6, a inibicao foi de 20, 7 e 70,6% para os isolados AP-3 e Ap-150 respectivamente, mostrando o efeito da concentracao de celulas do antagonista. Entretanto, precisa ser enfatizado que todos os tubos germinativos dos urediniosporos considerados germinados, tanto na diluicao 5,4 x 10 7 quanto 5,4 x 10 6, estavam totalmente deformados

Development of sequence characterized DNA markers linked to leaf rust (Hemileia vastatrix) resistance in coffee (Coffea arabica L.)

Coffee leaf rust due to Hemileia vastatrix is one of the most serious diseases in Arabica coffee (Coffea arabica). A resistance gene (S-H(3)) has been transferred from C. liberica into C. arabica. The present work aimed at developing sequence-characterized genetic markers for leaf rust resistance. Linkage between markers and leaf rust resistance was tested by analysing two segregating populations, one F-2 population of 101 individuals and one backcross (BC2) population of 43 individuals, derived from a cross between a susceptible and a SH3-introgressed resistant genotype. A total of ten sequence-characterized genetic markers closely associated with the SH3 leaf rust resistance gene were generated. These included simple sequence repeats (SSR) markers, sequence-characterised amplified regions (SCAR) markers resulting from the conversion of amplified fragment length polymorphism (AFLP) markers previously identified and SCAR markers derived from end-sequences of bacterial artificial chromosome (BAC) clones. Those BAC clones were identified by screening of C. arabica genomic BAC library using a cloned AFLP-marker as probe. The markers we developed are easy and inexpensive to run, requiring one PCR step followed by gel separation. While three markers were linked in repulsion with the S-H(3) gene, seven markers were clustered in coupling around the S-H(3) gene. Notably, two markers appeared to co-segregate perfectly with the S-H(3) gene in the two plant populations analyzed. These markers are suitable for marker-assisted selection for leaf rust resistance and to facilitate pyramiding of the S-H(3) gene with other leaf rust resistance genes

Germination and growth of Colletotrichum acutatum and Colletotrichum gloeosporioides isolates from coffee in Papua New Guinea and their pathogenicity to coffee berries

The biology and pathogenicity of Colletotrichum acutatum and C. gloeosporioides isolates from infected coffee berries with anthracnose in Papua New Guinea (PNG) was investigated in vitro and in vivo. Optimum germination in vitro occurred at concentrations of 1 x 10 conidia/mL, while germination was inhibited by 1 x 10 conidia/mL. Optimum germination of C. acutatum and C. gloeosporioides conidia occurred at temperatures between 21-29°C and 25-31°C respectively, after 18-24 h incubation periods, between pH5- pH7 and 100% RH. Maximum growth of C. acutatum occurred at 21°C and C. gloeosporioides at 25-31°C. Conidial germination increased in the presence of free water in both species. Colletotrichum acutatum produced abundant secondary conidia in culture. The process of infection of attached and detached coffee berries by conidia of C. gloeosporioides and C. acutatum was investigated and demonstrated to be equivalent for the two species. The optimum temperatures for conidia germination, appressoria formation and anthracnose development ranged between 25-31°C. Conidia germinated after 3-12 h, appressoria were formed after 6-48 h and anthracnose symptoms appeared 6 days after inoculation. Colletotrichum acutatum infected both non-wounded and wounded green and ripe red berries whereas C. gloeosporioides only infected ripe red non-wounded and wounded berries. This is the first report of C. acutatum as an etiological agent of coffee berry anthracnose