Indução de resistência à brusone em folhas de arroz por isolado avirulento de Magnaporthe oryzae

Abstract

A resistência a doenças pode ser induzida em plantas tanto por agentes abióticos como por agentes bióticos, por exemplo isolados avirulentos de patógenos. No presente trabalho objetivou-se determinar a concentração de um isolado avirulento (indutor) e o período necessário para induzir resistência em folhas de arroz a um isolado virulento de M. oryzae. Em casa de vegetação, plantas com 18 dias das cultivares Metica-1 e Cica-8 foram pulverizadas com um isolado indutor de resistência, nas concentrações de 0, 10(5), 3x10(5) e 6x10(5) conídios.mL-1 em períodos que antecederam a inoculação do isolado virulento de 24, 48 e 72 horas. A indução da resistência manifestou-se na redução da área foliar afetada e no tipo de lesão. O grau de indução de resistência foi maior na cultivar Metica-1 do que na cultivar Cica-8, em relação a suas respectivas testemunhas. A indução da resistência em Cica-8 foi superior quando o indutor foi aplicado 48 horas antes da aplicação do isolado virulento nas concentrações de 6x10(5) e 3x10(5) conídios.mL-1. Por outro lado, a indução de resistência em Metica-1 foi significativamente maior em todas as concentrações e períodos de aplicações do indutor quando comparados com a testemunha, mas não houve diferença entre os tratamentos de indução.

Increased enzymatic activity in rice leaf blast suppression by crude extract of Epicoccum sp

“…In addition, through molecular techniques it is possible to clone genes related to defense pathways of host plants such as elicitors by crude extract of Epicoccum sp., as well as fractions of crude extract responsible for antibiosis against rice pathogens. Various investigators provided evidence regarding the induction of SAR in rice after the application of microorganisms utilizing avirulent isolates of M. oryzae and Bipolaris sorokiniana (Smith & Métraux 1991;Manandhar et al, 1998;Tsukamoto et al, 1999;Ashizawa et al, 2005;Filippi et al, 2007) as well as ISR in rice with Pseudomonas fluorescens for the control of sheath blight (Nandakumar et al, 2000;Radjacommare et al, 2004), with rhizobacteria and with Bacillus sp. for leaf blast (Nascimento, 2009;Filippi et al, 2011).…”

“…The use of biotic and abiotic resistance inducers is one of the major strategies for increasing durability of disease resistance and to reduce toxic residues produced by the indiscriminate use of agricultural chemicals (Filippi et al, 2011). Studies on induction of acquired systemic resistance (SAR) and induced systemic resistance (ISR) in rice plants to M. oryzae were conducted after the application of avirulent isolates of M. oryzae, Bipolaris sorokiniana and rhizobacteria (Smith & Métraux 1991;Manandhar et al, 1998;Tsukamoto et al, 1999;Ashizawa et al, 2005;Filippi et al, 2007Filippi et al, , 2011.…”

“…Studies on the interaction between M. oryzae in rice and Epicoccum sp., and the mechanisms of in vivo biological control are important for the adoption of adequate control measures for rice blast which are ecologically sustainable (Filippi et al, 2007). The knowledge of the mode of action and mechanisms involved in disease reduction by potential biocontrol agents such as Epicoccum sp.…”

Results of 25 Years of Upland Rice Breeding in Brazil

“…Disease resistance, especially blast resistance, has been a major selection factor during the period under study. Rice blast (Magnaporthe oryzae) is the most aggressive pathogen of upland rice in Brazil (Filippi et al, 2007) such that blast susceptibility has always been a major factor for discarding breeding lines or preventing crosses between high-yielding cultivars that lack blast resistance. On the other hand, considering that VCU trials are not treated with fungicides, gains for disease resistance probably contributed to the observed gains for GY.…”

Sample Size for Assess the Leaf Blast Severity in Experiments With Irrigated Rice

“…The characteristic symptoms of the disease on the leaves are elliptical lesions with a gray center and reddish brown edges, with the reproductive structures (conidia) of the pathogen in the necrotic center (BEDENDO, 1997). The disease occurs in all rice-producing areas and results in yield losses that can reach 100% (FILIPPI et al, 2007). Owing to the high potential for damage caused by leaf blast on rice, research on fungicide efficiency is critical for proper disease management, as well as to find an alternative way to chemical control, which is one of the main methods to control rice leaf disease (CELMER et al, 2007;SANTOS et al, 2008).…”