Susceptibility of hairy root lines of Brassica species to Plasmodiophora brassicae and in an in vitro subculture system
ABSTRACT To investigate the susceptibility of hairy root lines of Brassica species to Plasmodiophora brassicae, hairy roots were induced in a number of Brassica species with Agrobacterium rhizogenes. Turnip hairy root was highly susceptible to P. brassicae; infection rates were high and large galls formed. In contrast, the rates of root hair infection and gall formation on intact
Brassica plants did not differ significantly from the control. To induce resting spore formation, turnip hairy roots were incubated
at 15°, 20°, or 25°C after 3 weeks of incubation at 25°C. The number and fresh mass of the galls per hairy root were higher
and formation of resting spores was greatest after a 7-week incubation at 20°C. To subculture P. brassicae using turnip hairy root, turnip hairy roots were reinoculated with resting spores and gall with resting spores then formed
on the hairy roots. In this way, P. brassicae using hairy roots could be subcultured in vitro two or three times on three single-spore isolates of P. brassicae. This is the first report of in vitro subculture of P. brassicae using hairy root.
- SourceAvailable from: scielo.brSumma Phytopathologica 01/2009; 35(1).
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ABSTRACT: The preservation of Plasmodiophora brassicae resistance structures under laboratory conditions is difficult since this is an obligate parasite. The freezing method using an ordinary household freezer was tested to ensure the pathogen's survival and the preservation of its infective traits. Roots of different brassica species naturally infected by P. brassicae, showing typical clubroot symptoms, sampled in the same farm, located in the Pardinho County, State of São Paulo, were collected during different seasons and were immediately frozen at approximately 20ºC. The treatments were divided as follows: T1: clubroots frozen for 389 days (arugula); T2: clubroots frozen for 242 days (broccoli); T3: clubroots frozen for 21 days (Chinese cabbage), and T4: control (without inoculum). The pathogenicity tests were conducted under greenhouse conditions (25±2ºC). Each plant of the susceptible variety of Chinese cabbage (Pak choi) was inoculated with 2mL of a spore suspension of each treatment at a concentration of 107 spores.mL-1. Each treatment consisted of six replicates distributed in random blocks. The roots of plants were washed and evaluated five weeks after inoculation. There were significant differences between treatments. The frozen materials preserved their infective traits over a period of 21 to 242 days, demonstrating that the freezing method could be an option to preserve the resistance structures of this pathogen.Summa Phytopathologica 02/2009; 35(1):57-59.
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ABSTRACT: This study aimed to evaluate propensity of the Curitiba Metropolitan Region (26 cities) to the clubroot of crucifers incidence, through soil pH values. The 14452 pH in CaCl2 analyses were held by the Laboratory of Chemistry and Soil Fertility (DSEA / SCA / UFPR) during the period of 1999 and 2007. To check the disease incidence and severity propensity, there were faced the tendency measures with pH bands preset by literature. Except for Adrianópolis (59.4%) and Dr. Ulysses(33.3%), the other districts studied presented high propensity for the disease in its highest severity degree (pH < 5,7), with probability values higher than 75%. The results emphasized the necessity of liming and otherpractices of disease control.Scientia Agraria. 01/2009; 10(6):499-505.