Summary
A new disease of unknown bacterial aetiology has been observed in eucalyptus stands since 2009. It is characterized by die‐back, wilting and lesions on the branches, petiole and midrib in association with macroscopic and microscopic bacterial ooze. To date, this disease has been observed in stands of clonal Eucalyptus saligna, E. grandis and E. urophylla x E. grandis hybrids and in E. dunnii seedling plantations in the states of São Paulo, Rio Grande do Sul and Mato Grosso do Sul. Considering the economic importance of eucalyptus plantations and the potential losses caused by this disease, this study aimed to identify and characterize the causal agent. Thirty‐four strains were obtained from infected plants, which were collected in the field from four locations. The inoculation of detached leaves and intact rooted cuttings supported pathogenicity in eucalyptus. The phylogenetic analysis of four housekeeping genes (16S rDNA, gapA, recA and rpoB) as well as biochemical tests confirmed the identity of strains belonging to the species Erwinia psidii. This is the first report of E. psidii as the cause of wilt and die‐back in Eucalyptus spp. in Brazil.
A new foliar disease caused by Teratosphaeria pseudoeucalypti on eucalyptus (E. globulus, E. urophylla x E. globulus and E. nitens x E. globulus) in Brazil is described. The disease is characterized by leaf spots of variable sizes and shapes, resulting in leaf blight and premature defoliation. Based on the morphological characteristics and multilocus phylogenetic analysis of the EF-1α, β-T and ITS-2 gene regions of five isolates, the fungus was identified as T. pseudoeucalypti. This is the first report of this pathogen outside Australia and a method for sporulation in culture is described.
A acácia-negra (Acacia mearnsii De Wild.) é uma espécie de difícil micropropagação devido à pequena capacidade de multiplicação e desenvolvimento de gemas. O presente estudo visou determinar a influência de diferentes citocininas na proliferação de gemas axilares em segmentos nodais de A. mearnsii. Plântulas germinadas in vitro forneceram explantes que foram inoculadas em meio básico B5 (GAMBORG et al., 1968). Testaram-se as citocininas: BAP (6-benzilaminopurina), BA (6-benziladenosina), 2iP (gama,gama-isopenteniladenina) e cinetina (6-furfuralamino-purina). Diferentes concentrações desses reguladores de crescimento foram empregadas: 1 mgL-1, 2 mgL-1 e 3 mgL-1. Utilizou-se o delineamento de blocos casualizados, em arranjo fatorial, com seis repetições e cinco plantas por parcela. As avaliações foram feitas aos 30 dias, através da contagem de gemas alongadas e da presença de calos. A utilização de BAP a 2 mgL-1 promoveu a maior taxa de multiplicação de gemas (3,5 brotos/explante).
Dieback caused by Erwinia psidii is currently one of the most important emerging diseases in eucalypt plantations in Brazil. However, little is known in terms of the host range of this pathogen or the potential sources of resistance against the disease it causes. In this study, we inoculated plants of species from nine families to gain insight into the host range of E. psidii. Plants of all inoculated species of Myrtaceae except Acca sellowiana exhibited disease symptoms and therefore represent potential hosts for the pathogen under natural conditions. In addition, the response of four Corymbia species, 29 Eucalyptus species and three interspecific Eucalyptus hybrids to inoculation with E. psidii was evaluated. All Corymbia henryi, Corymbia maculata, Eucalyptus thozetiana, Eucalyptus cloeziana, Eucalyptus viminalis, Eucalyptus dalrympleana and Eucalyptus pilularis plants were highly resistant to the pathogen, whereas differential disease resistance was observed in the other species. This study provides important information on sources of resistance to Erwinia psidii with potential use in the development of clones with enhanced resistance in eucalypt species of economic importance.
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