Abstract:Observações com microscopia eletrônica de transmissão em secções ultrafinas de células de caules de feijoeiros (Phaseolus vulgaris L.), inoculados com Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), mostraram alterações nos vasos de xilema em genótipos de feijoeiros altamente resistentes, como formação de estrutura semelhante a tilose e presença de fibrilas ao redor das células bacterianas. Em genótipos suscetíveis, Cff colonizou além de vasos de xilema, células parenquimáticas e metaxilema.
“…The authors studied the xylem vessels in stems of Cff-resistant cultivars and detected the presence of clumps in bacterial cells involved in filament and lace-like structures under marks in the walls of xylem vessels, which blocked the movement of bacteria to other parts of the xylem vessel, away from the point of inoculation. According to Souza and Maringoni (2008), protoplasmic projections are formed towards the inside of xylem vessels in Cff-resistant bean genotypes, indicating the onset of tylose formation and clogging of xylem vessels that restrict bacteria colonization.…”
Reaction and colonization of common bean genotypes by
INTRODUCTIONBrazil is one of the world's leading common bean producers and consumers, with a harvest of almost three million tons in 2012, in the main producing states of Paraná, Minas Gerais, São Paulo and Goiás (Agrianual 2013). Bacterial diseases are among the yield-limiting factors of the crop in the country, particularly bacterial wilt. This disease is caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), and was first described by Hedges (1922) in the USA. Currently, the disease has already been detected in several countries (EPPO 2011) and Brazilian states (Valentini et al. 2010). Bacterial wilt colonizes the xylem vessels of the affected plants, leading to disruption and degradation of the primary xylem. Infected plants show symptoms of wilting leaves, which later evolve to withering and death (Dinesen 1978). Yield losses in susceptible cultivars can be close to 50% (Miranda Filho 2006). Bacterial wilt is controlled by preventive measures, e.g., by using healthy seeds, incorporation of crop bean residues into the soil, crop rotation with non-host species, and by using cultivars with some level of resistance (Huang et al. 2009, Valentini et al. 2010.A number of studies identified Cff-resistant common bean genotypes in Brazil. According to Maringoni (2002), high resistance levels were observed in the cultivars IAC Carioca Akytã, IAC Carioca Aruã, and IAC Carioca Pyatã. Souza et al. (2006) Carioca Aruã, IAC Carioca Pyatã, and IAC Carioca Tybatã, whose resistance reactions were found to be as described by Maringoni (2002) and Souza et al. (2006).
“…The authors studied the xylem vessels in stems of Cff-resistant cultivars and detected the presence of clumps in bacterial cells involved in filament and lace-like structures under marks in the walls of xylem vessels, which blocked the movement of bacteria to other parts of the xylem vessel, away from the point of inoculation. According to Souza and Maringoni (2008), protoplasmic projections are formed towards the inside of xylem vessels in Cff-resistant bean genotypes, indicating the onset of tylose formation and clogging of xylem vessels that restrict bacteria colonization.…”
Reaction and colonization of common bean genotypes by
INTRODUCTIONBrazil is one of the world's leading common bean producers and consumers, with a harvest of almost three million tons in 2012, in the main producing states of Paraná, Minas Gerais, São Paulo and Goiás (Agrianual 2013). Bacterial diseases are among the yield-limiting factors of the crop in the country, particularly bacterial wilt. This disease is caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), and was first described by Hedges (1922) in the USA. Currently, the disease has already been detected in several countries (EPPO 2011) and Brazilian states (Valentini et al. 2010). Bacterial wilt colonizes the xylem vessels of the affected plants, leading to disruption and degradation of the primary xylem. Infected plants show symptoms of wilting leaves, which later evolve to withering and death (Dinesen 1978). Yield losses in susceptible cultivars can be close to 50% (Miranda Filho 2006). Bacterial wilt is controlled by preventive measures, e.g., by using healthy seeds, incorporation of crop bean residues into the soil, crop rotation with non-host species, and by using cultivars with some level of resistance (Huang et al. 2009, Valentini et al. 2010.A number of studies identified Cff-resistant common bean genotypes in Brazil. According to Maringoni (2002), high resistance levels were observed in the cultivars IAC Carioca Akytã, IAC Carioca Aruã, and IAC Carioca Pyatã. Souza et al. (2006) Carioca Aruã, IAC Carioca Pyatã, and IAC Carioca Tybatã, whose resistance reactions were found to be as described by Maringoni (2002) and Souza et al. (2006).
“…According to Souza and Maringoni (2008), resistant genotypes involve the pathogen by protoplasmic projections, preventing its installation in the xylem vessels, while in susceptible genotypes the water transport is obstructed by the presence of bacterial cells. These results are related to the disease symptoms, e.g., plant wilting, yellowing, underdevelopment, and death, observed at different levels of aggressiveness in the 58 lines evaluated in this study.…”
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