نوع مقاله : مقاله پژوهشی
نویسنده
بخش تحقیقات گیاهپزشکی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی چهارمحال و بختیاری، سازمان تحقیقات، آموزش و ترویج کشاورزی، شهرکرد، ایران.
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسنده [English]
Bacterial canker of stone fruit trees caused by Pseudomonas syringae pv. syringae (Pss) interacts with several factors such as ring nematodes. The effect of infection of Mesocriconema xenoplax (Mx) and Pss and co-infection in pot conditions in the greenhouse on peach bacterial canker was investigated on GN and GF677 rootstocks, tolerant and susceptible to Mx, respectively. One-year peach seedlings (cv. Zaafarani), susceptible to Pss, grafted on these rootstocks were used. Infection treatments included nematode inoculation, bacterial inoculation, and inoculation with both pathogens. The experiment was conducted as a factorial in a completely randomized design with five replications. The results were evaluated and compared statistically based on disease severity, bud death, seedling height, root weight, total plant weight, and population of Mx in soil. The results showed a significant difference between GN and GF677 in terms of response to pathogen inoculation (s) based on evaluation indexes. In both vegetative rootstocks, canker severity and dead bud in seedlings co-inoculated with Mx and Pss were more than those only inoculated with Pss alone. In seedlings with GF677 rootstock, in infection with both pathogens, the rate of canker progression up to about 30 cm was measured and dieback was observed. In inoculation with only Mx and Pss, there was a significant difference in plant growth indexes (in both treatments) and nematode population and disease severity between the two rootstocks for inoculation with nematode and bacteria. Therefore, it can be concluded that Mx is a synergistic factor for peach trees (especially at a susceptible rootstock) to aggravate bacterial canker disease caused by Pss.
کلیدواژهها [English]
Extended Abstract
Introduction
The high population of ring nematode (Mesocriconema xenoplax (Mx)) is one of the possible live factors as a predisposing of bacterial canker of peach in sandy soils. In peach trees inoculated with ring nematodes, sensitivity to Pseudomonas syringae pv. syringae (Pss) increases with increasing canker length. Susceptibility to bacterial canker has also been observed in prunes and almonds infected with ring nematodes. However, the mechanism by which the presence of ring nematodes causes stress on stone fruit trees and is susceptible to bacterial canker is not known. The type of rootstock has a significant effect on the amount and severity of bacterial canker in stone fruit trees. The rootstock's role in the reaction of living and non-living factors in the soil such as soil acidity, soil texture, and ring nematodes soil affects the occurrence and severity of bacterial canker disease.
Materials and Methods
In this study, the effect of co-infection of Mx and Pss in pot conditions on peach bacterial canker was investigated on GN and GF677 rootstocks, tolerant and susceptible to Mx, respectively. One-year peach seedlings (cv. Zaafarani), susceptible to Pss, grafted on these rootstocks were used. Infection treatments included three groups’ nematode inoculation, bacterial inoculation, and inoculation with both pathogens. The results were evaluated and compared statistically based on disease severity, bud death, seedling height, root weight, total plant weight, and population of Mx per cm3 of soil.
Results and Discussion
The results showed a significant difference between GN and GF677 in terms of response to pathogen(s) inoculation based on evaluation indexes. In both vegetative rootstocks, canker severity and dead bud in seedlings co-inoculated with Mx and Pss were more than those only inoculated with Pss alone. In seedlings with GF677 rootstock, in infection with both pathogens, the rate of canker progression up to about 30 cm was measured and dieback was observed. Therefore, it can be said that Mx is a synergistic factor for peach trees (especially at a susceptible rootstock) to aggravate bacterial canker disease caused by Pss. Field studies in Chaharmahal and Bakhtiary province showed that in almond and peach orchards replanted with GN rootstock, the vegetative growth of trees is higher and canker disease is lower than trees with GF677rootstock. In this study, in pot conditions, growth indexes in GN (nematode-resistant) rootstock inoculated with Mx showed a significant difference with GF677 (nematode-susceptible) rootstock. This difference was also evident in co-inoculation Mx and Pss. The short life of trees in some stone fruit species such as peach and plum has been attributed to the interaction Pss causal agent of bacterial canker and other living factors, especially Mx, and there is various evidence for the role of Mx in the short life of these plants. In this study, the severity of canker disease on peach (Zaafarani cv.) in Mx and Pss co-inoculation treatment was significantly higher in GN (high root volume) and GF677 (low root volume), compared to infected treatments with one of the above pathogens increased. Based on the results of this study, it can be said that the use of rootstocks and tolerant rootstocks such as GN to Mx is effective in the integrated management of peach bacterial canker to reduce the population of plant parasitic nematodes. Because the Mx nematode and the Pss strains that cause the canker of stone fruit trees are distributed in all regions of Iran, the results of this study can be generalized to the climatic regions of Chaharmahal and Bakhtiary province in Iran.
Conclusion
According to the results of previous studies, the frequency and population of Mx on stone fruit trees with bacterial canker symptoms in Chaharmahal and Bakhtiary province are higher than other nematodes and the most important disease and causal short life peach in these regions is canker, on the other hand, Mx nematode has been proven as a predisposing factor for bacterial canker caused by Pss, based on the results of this study, it can be said that the use of rootstocks and tolerant rootstock such as GN to Mx is effective in integrated management of peach bacterial canker to reduce the population of plant parasitic nematodes.
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