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Genetic variation for induced and basal resistance against leaf pathogen Pseudomonas syringae pv. tomato DC3000 among Arabidopsis thaliana accessions.

Hossain MM, Sultana F - Springerplus (2015)

Bottom Line: In Arabidopsis thaliana, significant efforts to determine the effect of naturally occurring variation between phenotypically divergent accessions on different biotic or abiotic stresses are underway.On the contrary, about a two-third of the accessions (49 accessions) showed a reduction in infected leaf number, disease severity and pathogen proliferation after treatment with GP17-2, indicating that GP17-2 induction of resistance is ecotype specific in Arabidopsis.Future study with these parental lines employing a variety of crossing schemes may facilitate identification of major trait loci responsible for GP17-2-mediated ISR in Arabidopsis.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, 1706 Bangladesh.

ABSTRACT
In Arabidopsis thaliana, significant efforts to determine the effect of naturally occurring variation between phenotypically divergent accessions on different biotic or abiotic stresses are underway. Although it is usually assumed that induced systemic resistance (ISR) against pathogen will covary with plant genetic variation, this assumption has not been tested rigorously in previous experiments. Here, we investigated heritable variation in resistance as well as Penicillium simplicissimum GP17-2-mediated ISR to the bacteria Pseudomonas syringae pv. tomato DC3000 (Pst) among a worldwide collection of accessions of A. thaliana. In this study, 75 Arabidopsis accessions were screened against the bacteria Pst following induction and non-induction treatment and their resistance levels were determined by measuring three components of A. thaliana resistance (infected leaf number, disease severity and pathogen growth). We observed extensive quantitative variation in the number of infected leaves, severity of disease symptoms and the bacterial population size among 75 accessions of A. thaliana infected with Pst. On the contrary, about a two-third of the accessions (49 accessions) showed a reduction in infected leaf number, disease severity and pathogen proliferation after treatment with GP17-2, indicating that GP17-2 induction of resistance is ecotype specific in Arabidopsis. The level of suppression was more pronounced for percent disease severity and pathogen proliferation than for number of infected leaves in ISR-inducible accessions. Accessions non-responsive to GP17-2 treatment generally appeared to be associated with higher basal resistance to infection by Pst. Future study with these parental lines employing a variety of crossing schemes may facilitate identification of major trait loci responsible for GP17-2-mediated ISR in Arabidopsis.

No MeSH data available.


Related in: MedlinePlus

Correlation between the percent disease severity in control-treated accessions and the resulted percent reduction in disease severity in the same plants conferred by P. simplicissimum GP17-2 treatment. Three data points are shown for each of 75 plant lines in the scatterplot, N = 75 × 3 = 225. The percent reduction in disease severity due to GP17-2 treatment was calculated as follows: % Reduction = [1 − (Disease severity in treated plant/Disease severity in control plant)] × 100.
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Fig5: Correlation between the percent disease severity in control-treated accessions and the resulted percent reduction in disease severity in the same plants conferred by P. simplicissimum GP17-2 treatment. Three data points are shown for each of 75 plant lines in the scatterplot, N = 75 × 3 = 225. The percent reduction in disease severity due to GP17-2 treatment was calculated as follows: % Reduction = [1 − (Disease severity in treated plant/Disease severity in control plant)] × 100.

Mentions: Analysis was made to determine how far expression of GP17-2-mediated ISR depends on the level of basal resistance in Arabidopsis ecotypes to Pst. Percent infected leaves and symptom severity due to Pst infection are equivalent phenotypic indicators of host basal resistance to the bacterium. When a large number of accessions is used, the estimation of infected leaf number will considerably save time compared to that of disease severity. However, the variation in basal resistance with respect to disease severity was much wide ranging than to number of infected leaves. Therefore, disease severity provides more appropriate phenotype of basal resistance in ecotypes to Pst infection. Based on the mean disease severity in control-treated plants, individual accession was hypothetically categorized as either highly susceptible, moderately susceptible (70–40%) or lowly susceptible (<40%). Infection phenotypes with disease severity >70% were classified as highly susceptible and those with disease severity of 70–40% and <40% were classified as moderately and lowly susceptible, respectively (Table 2). Out of 75 accessions evaluated, 25 accessions were found to fall within highly susceptible group. Of the remaining accessions, 23 accessions were moderately susceptible and 27 were lowly susceptible. Among the 25 highly susceptible accessions, 24 (96%) showed significant level of GP17-2-mediated ISR against Pst, when disease severity was compared between GP17-2-treated and non-treated plants (Table 2). Similarly, out of 23 moderately susceptible accessions group, 20 (86.95%) showed significantly reduced disease severity in GP17-2-treated plants compared to non-treated plant (Table 2). On the other hand, only 5 (18.5%) of 27 lowly susceptible accessions were responsive to GP17-2-treatment in showing significant level of ISR against the bacterium (Table 2). These indicate that most plants have higher expression of GP17-2-mediated ISR despite higher degrees of infection. The Chi Square (χ2 = 10.36; df = 2; 0.001 < P<0.010) test revealed a significant difference in ISR-responsiveness among different Pst susceptibility accession groups in Arabidopsis. In other words, ISR-responsiveness was not equally distributed across the different levels of host susceptibility in Arabidopsis accessions towards Pst. Accessions that had higher Pst susceptibility were likely to be more ISR-responsive than accessions that had less susceptibility. In order to elucidate a clear functional relationship between the host basal resistance and the GP17-2-induced ISR responsiveness of Arabidopsis ecotypes, we calculated the correlation between the symptom severity in control-treated ecotypes and the reduction in symptom severity in GP17-2-treated plants. There was a significant positive relationship observed between the symptom severity in control-treated ecotypes and the reduction in symptom severity due to GP17-2 treatment in the same plants, r (223) = 0.84, P < 0.000. That means percent reduction in symptom severity in ISR-inducible ecotypes linearly increased as percent disease severity increased in control-treated plants. Among all accessions, 70% of the values fit the model (Figure 5). These results indicate the ISR-inducible phenotype of Arabidopsis ecotypes was highly correlated with a relatively low level of basal resistance against Pst.Table 2


Genetic variation for induced and basal resistance against leaf pathogen Pseudomonas syringae pv. tomato DC3000 among Arabidopsis thaliana accessions.

Hossain MM, Sultana F - Springerplus (2015)

Correlation between the percent disease severity in control-treated accessions and the resulted percent reduction in disease severity in the same plants conferred by P. simplicissimum GP17-2 treatment. Three data points are shown for each of 75 plant lines in the scatterplot, N = 75 × 3 = 225. The percent reduction in disease severity due to GP17-2 treatment was calculated as follows: % Reduction = [1 − (Disease severity in treated plant/Disease severity in control plant)] × 100.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481244&req=5

Fig5: Correlation between the percent disease severity in control-treated accessions and the resulted percent reduction in disease severity in the same plants conferred by P. simplicissimum GP17-2 treatment. Three data points are shown for each of 75 plant lines in the scatterplot, N = 75 × 3 = 225. The percent reduction in disease severity due to GP17-2 treatment was calculated as follows: % Reduction = [1 − (Disease severity in treated plant/Disease severity in control plant)] × 100.
Mentions: Analysis was made to determine how far expression of GP17-2-mediated ISR depends on the level of basal resistance in Arabidopsis ecotypes to Pst. Percent infected leaves and symptom severity due to Pst infection are equivalent phenotypic indicators of host basal resistance to the bacterium. When a large number of accessions is used, the estimation of infected leaf number will considerably save time compared to that of disease severity. However, the variation in basal resistance with respect to disease severity was much wide ranging than to number of infected leaves. Therefore, disease severity provides more appropriate phenotype of basal resistance in ecotypes to Pst infection. Based on the mean disease severity in control-treated plants, individual accession was hypothetically categorized as either highly susceptible, moderately susceptible (70–40%) or lowly susceptible (<40%). Infection phenotypes with disease severity >70% were classified as highly susceptible and those with disease severity of 70–40% and <40% were classified as moderately and lowly susceptible, respectively (Table 2). Out of 75 accessions evaluated, 25 accessions were found to fall within highly susceptible group. Of the remaining accessions, 23 accessions were moderately susceptible and 27 were lowly susceptible. Among the 25 highly susceptible accessions, 24 (96%) showed significant level of GP17-2-mediated ISR against Pst, when disease severity was compared between GP17-2-treated and non-treated plants (Table 2). Similarly, out of 23 moderately susceptible accessions group, 20 (86.95%) showed significantly reduced disease severity in GP17-2-treated plants compared to non-treated plant (Table 2). On the other hand, only 5 (18.5%) of 27 lowly susceptible accessions were responsive to GP17-2-treatment in showing significant level of ISR against the bacterium (Table 2). These indicate that most plants have higher expression of GP17-2-mediated ISR despite higher degrees of infection. The Chi Square (χ2 = 10.36; df = 2; 0.001 < P<0.010) test revealed a significant difference in ISR-responsiveness among different Pst susceptibility accession groups in Arabidopsis. In other words, ISR-responsiveness was not equally distributed across the different levels of host susceptibility in Arabidopsis accessions towards Pst. Accessions that had higher Pst susceptibility were likely to be more ISR-responsive than accessions that had less susceptibility. In order to elucidate a clear functional relationship between the host basal resistance and the GP17-2-induced ISR responsiveness of Arabidopsis ecotypes, we calculated the correlation between the symptom severity in control-treated ecotypes and the reduction in symptom severity in GP17-2-treated plants. There was a significant positive relationship observed between the symptom severity in control-treated ecotypes and the reduction in symptom severity due to GP17-2 treatment in the same plants, r (223) = 0.84, P < 0.000. That means percent reduction in symptom severity in ISR-inducible ecotypes linearly increased as percent disease severity increased in control-treated plants. Among all accessions, 70% of the values fit the model (Figure 5). These results indicate the ISR-inducible phenotype of Arabidopsis ecotypes was highly correlated with a relatively low level of basal resistance against Pst.Table 2

Bottom Line: In Arabidopsis thaliana, significant efforts to determine the effect of naturally occurring variation between phenotypically divergent accessions on different biotic or abiotic stresses are underway.On the contrary, about a two-third of the accessions (49 accessions) showed a reduction in infected leaf number, disease severity and pathogen proliferation after treatment with GP17-2, indicating that GP17-2 induction of resistance is ecotype specific in Arabidopsis.Future study with these parental lines employing a variety of crossing schemes may facilitate identification of major trait loci responsible for GP17-2-mediated ISR in Arabidopsis.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, 1706 Bangladesh.

ABSTRACT
In Arabidopsis thaliana, significant efforts to determine the effect of naturally occurring variation between phenotypically divergent accessions on different biotic or abiotic stresses are underway. Although it is usually assumed that induced systemic resistance (ISR) against pathogen will covary with plant genetic variation, this assumption has not been tested rigorously in previous experiments. Here, we investigated heritable variation in resistance as well as Penicillium simplicissimum GP17-2-mediated ISR to the bacteria Pseudomonas syringae pv. tomato DC3000 (Pst) among a worldwide collection of accessions of A. thaliana. In this study, 75 Arabidopsis accessions were screened against the bacteria Pst following induction and non-induction treatment and their resistance levels were determined by measuring three components of A. thaliana resistance (infected leaf number, disease severity and pathogen growth). We observed extensive quantitative variation in the number of infected leaves, severity of disease symptoms and the bacterial population size among 75 accessions of A. thaliana infected with Pst. On the contrary, about a two-third of the accessions (49 accessions) showed a reduction in infected leaf number, disease severity and pathogen proliferation after treatment with GP17-2, indicating that GP17-2 induction of resistance is ecotype specific in Arabidopsis. The level of suppression was more pronounced for percent disease severity and pathogen proliferation than for number of infected leaves in ISR-inducible accessions. Accessions non-responsive to GP17-2 treatment generally appeared to be associated with higher basal resistance to infection by Pst. Future study with these parental lines employing a variety of crossing schemes may facilitate identification of major trait loci responsible for GP17-2-mediated ISR in Arabidopsis.

No MeSH data available.


Related in: MedlinePlus