Ramulosis of cotton, caused by Colletotrichum gossypii var. cephalosporioides (CGC), is an important disease of cotton in Brazil. The main objective of this work was to test whether CGC is a phylogenetic species inside the Colletotrichum gloeosporioides species complex. A Bayesian inference phylogenetic analysis of a combined ITS and TUB2 dataset was conducted with 21 strains identified as CGC and five strains of Colletotrichum gossypii (CG), associated with cotton anthracnose, obtained from diseased plants from different regions of Brazil. All CGC strains formed a highly supported lineage inside the clade of Colletotrichum theobromicola, a member of the C. gloeosporioides species complex. CG strains formed another lineage in the same clade. These findings were supported by a second analysis conducted with three genes (ITS+TUB2+GAPDH) and a subset of five CGC and three CG strains. During pathogenicity tests, all five CGC strains tested induced typical symptoms of ramulosis on inoculated plants, including foliar necrosis, death of apical meristems and over sprouting. Plants inoculated with CG strains exhibited foliar necrotic spots two months after inoculation. These results give phylogenetic support for the placement of CGC in the C. gloeosporioides species complex, and the distinction between the ramulosis and anthracnose pathogens of cotton in Brazil.

Objetivou-se, neste trabalho, estudar, em ambiente controlado, as diferenças na intensidade de doenças e na expansão da pústula de dois acessos de Hemileia vastatrix, coletados em plantas da cultivar Catuai das cidades de Coromandel (COR2), no Alto Paranaíba e de Ijaci (IIJ1), no Sul de Minas Gerais. As plantas inoculadas foram submetidas a três temperaturas (15, 20 e 25ºC) e três períodos de molhamento foliar (24, 48 e 72 horas de molhamento foliar), em esquema fatorial com três repetições. Ambos os acessos apresentaram maior severidade da doença quando submetidos a 24 horas de molhamento foliar, após a inoculação. A maior freqüência de infecção do IIJ1 foi a 15ºC, no entanto, a temperatura não influenciou essa variável para COR2. Houve maior severidade da ferrugem em COR2 a 25ºC. A maior expansão da pústula, em folhas inoculadas com IIJ1, foi a 15ºC com 7,59cm², e a menor a 25 ºC, com 5,37cm², enquanto para COR2 houve aumento à medida que se elevou a temperatura de 15 para 25ºC, de 1,44 para 6,62 cm², respectivamente. Accessos provenientes de Ijaci e de Coromandel apresentaram diferenças na intensidade da ferrugem e na expansão das pústulas em ambiente controlado.

The aim of this work was to study, under controlled environment, the differences in the disease intensity and pustule expansion of two Hemileia vastatrix accesses, sampled in cultivar Catuai coffee (Coffea arabica L.) plants from Coromandel (COR2) and Ijaci (IIJ1), towns located respectively in the West and South of Minas Gerais State. The inoculated plants were submitted to three temperatures (15, 20 and 25ºC) and three leaf wetness durations (24, 48 e and 72 hours) in a factorial scheme with three replicates. Both accesses presented a higher disease severity when submitted to 24h leaf wetness duration after inoculation. The higher infection frequency for IIJ1 was at 15ºC, while the temperature did not influence this variable for COR2. There was a higher severity for COR2 inoculated plants when incubated at 25ºC. The higher pustule expansion, for leaves inoculated with IIJ1 was at 15ºC with 7.59cm² and a lower at 25ºC, with 5.37cm², while for COR2 when temperature raised from 15 to 25ºC, there was an increase in the pustule expansion from 1.44 to 6.62 cm², respectively. Fungal lines from Ijaci and from Coromandel presented differences in the intensity and pustule expansion of rust, under controlled environment.

Neste trabalho, objetivou-se verificar o efeito da temperatura na germinação e no comprimento do tubo germinativo em diferentes populações de H. vastatrix (PHVs), sob quatro temperaturas. Realizou-se um bioensaio com dez PHVs, com suspensão de urediniósporos a 0,5mg/mL em solução aquosa (0,05%) de tween 80. Duas gotas de cada suspensão foram depositadas em lâminas de microscópio recobertas com camada de poliestireno e colocadas em gerbox contendo papel de filtro umedecido para constituir câmara úmida. Os gerboxes foram mantidos fechados, no escuro, a 15ºC, 20ºC, 25ºC e 30ºC, por 24 horas. O ensaio foi conduzido em fatorial 10 x 4, sendo dez isolados, quatro temperaturas e duas repetições. Avaliaram-se a germinação e o comprimento do tubo germinativo. Houve variabilidade entre as PHVs quanto à temperatura ótima para germinação e alongamento do tubo germinativo.

The objective of this work was to verify the effect of temperature in germination and germ tube length in different populations of H. vastatrix (PHVs) temperatures. A bioassay was performed with ten PHVs, using an urediniospore suspension of at 0.5mg/mL in aqueous solution (0.05%) of tween 80. Two drops of each suspension was deposited on a microscope coverslip, covered with a polystyrene layer and incubated in gerbox containing a watered filter paper to work as a wet chamber. The gerbox was kept closed, in the dark, at 15, 20, 25 and 30ºC for 24 hours. The assay was carried out in a factorial design 10 x 4, with ten isolates, four temperatures and two replicates represented by two drops of the suspension. Germination percentage and germ tube length were assessed. There was variability among PHVs for the optimum temperature for germination and elongation of the germ tube.