نوع مقاله : مقاله پژوهشی

نویسندگان

• محبوبه آفروشه ¹
• ناصر رادمان ¹
• امیرحسین محمدی ²
• عبدالحسین طاهری ³
• مهدی فاطمی ⁴
• مهدی پیرنیا ⁵

¹ گروه بیماری شناسی گیاهی، دانشکده کشاورزی، دانشگاه زابل، زابل، ایران

² پژوهشکده پسته، موسسه تحقیقات علوم باغبانی، سازمان تحقیقات، آموزش و ترویج کشاورزی، رفسنجان، ایران

³ گروه گیاهپزشکی، دانشکده تولید گیاهی، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران

⁴ گروه آب و خاک، معاونت برنامه ریزی سازمان جهاد کشاورزی خراسان رضوی، مشهد. ایران

⁵ گروه بیماری شناسی گیاهی ، دانشکده کشاورزی، دانشگاه زابل، زابل، ایران

چکیده

کلیدواژه‌ها

• بیماری‌های خاکزاد
• پوسیدگی قارچ عسلی
• رایزومورف
• همزیستی

عنوان مقاله [English]

Effect of arbuscular mycorrhizal fungi inoculation on Armillaria root rot of pistachio seedlings under salinity stress

نویسندگان [English]

• Mahboobeh Afrousheh ¹
• Naser Radman ¹
• Amir Hossein Mohammadi ²
• Abdol Hossein Taheri ³
• Mehdi Fatemi ⁴
• Mahdi Pirnia ⁵

کلیدواژه‌ها [English]

• Soil-borne diseases
• Honey Fungus Rot
• Rhizomorph
• Symbiosis

Extended Abstract

Introduction

    Salinity constitutes one of the most significant abiotic stresses in pistachio orchards, inflicting economic losses through both direct (disruption of physiological processes) and indirect pathways (by predisposing plants to plant pathogens and diminishing their tolerance).

Armillaria root and crown rot, caused by Armillaria mellea, is a major disease prevalent in the pistachio orchards of Kerman, Semnan, Tehran, and Isfahan provinces, and can result in tree mortality. The control of this disease is profoundly difficult and costly due to the broad host range, various ecological phases (pathogenic, saprophytic, and orchid-like symbiotic) of the pathogen, and the presence of rhizomorphs.

The application of arbuscular mycorrhizal fungi (AMF) in various plants, including pistachio trees, is an increasingly prevalent strategy. This is due to its demonstrated role in enhancing host resistance to soil-borne diseases and improving tolerance to stresses such as salinity and drought. This symbiotic association plays a significant role in mitigating crop losses from diseases and reduces the environmental hazards associated with chemical pesticide usage.

Arbuscular Mycorrhizal (AM) fungi enhance plant tolerance to biotic and abiotic stresses through a multitude of mechanisms. These include the improvement of growth, nutritional, and biochemical status of the host plant, as well as the activation of defense-related enzymes.

In the present study, the effect of inoculation with a mixture of three species of arbuscular mycorrhizal fungi on Armillaria root and crown rot of Ahmad-Aghaei pistachio seedlings under saline conditions was investigated for the first time.

Materials and Methods

    This research was conducted as a factorial experiment in a completely randomized design with five replications under greenhouse conditions. Treatments included inoculation of a mixture of three arbuscular mycorrhizal fungi species (Claroideoglomus etunicatum, Funneliformis mosseae, and Rhizophagus irregularis), Armillaria mellea and four salinity levels (0, 1200, 2400, and 3600 mg NaCl per kg of soil. The inoculum of AMF was a perlite-based medium containing a minimum of 100 infective propagules per gram from each species in equal proportions. Armillaria mellea isolate (listed in the GenBank database on NCBI under the code OL377854) was isolated from infected pistachio trees in Sirjan. Seeds of pistachio (cv. Ahmad Aghaei) were planted in a substrate (mixture of sterile virgin soil and sand, 1:2 w/w) containing 5% (w/w) AMF propagules. After two months, NaCl solutions (0, 1200, 2400, and 3600 mg/kg soil) were gradually applied within one month via irrigation. For pathogen inoculation, the soil around each seedling was carefully removed to a depth of 15 cm, and two apple twigs colonized with A. mellea were placed near the roots of each seedling. Four months after pathogen inoculation, shoot and root dry weight, leaf area, plant height, total chlorophyll, proline content, soluble sugars, mycorrhizal colonization, root colonization percentage by
A. mellea and seedling mortality rate were assessed. Data were analyzed using SAS (ver. 9.1), Duncan’s multiple range test (P< 0.05).

Results and Discussion

    The results demonstrated that inoculation of arbuscular mycorrhizal fungi (AMF) significantly increased shoot and root dry weight, leaf area, plant height, total chlorophyll, proline content, and soluble sugars compared to non-inoculated (control) and pathogen-inoculated plants (Arm) under both saline and non-saline conditions. In the absence of A. mellea, increasing NaCl concentration significantly reduced AMF root colonization in pistachio seedlings. At 3600 mg NaCl/kg soil, the percentage of colonized roots and root colonization length by AMF were 77.25% and 64%, respectively, showing a significant decrease compared to the non-saline treatment (90.75% and 98.25%). The same trend was observed in the presence of the pathogen treatment (AM+Arm). The percentage of colonized roots in the AM + Arm treatment was significantly lower than in the AM treatment at all salinity levels. However, root colonization length only showed a significant decrease at the highest NaCl concentration (3600 mg/kg), indicating the detrimental effects of combined salinity and pathogen stress on AMF colonization. The highest root colonization (86.8%) and seedling mortality (93.8%) caused by A. mellea were observed in the pathogen-inoculated treatment (Arm) at 3600 mg NaCl/kg soil, demonstrating the stimulatory effect of salinity on pathogen activity and disease severity. Although a similar trend was observed in the AM+Arm treatment, both root colonization and seedling mortality were significantly lower than in the pathogen treatment (Arm), clearly indicating the protective role of AMF in mitigating pathogen damage under both saline and non-saline conditions.

Conclusions

    The enhancement of growth and biochemical characteristics in mycorrhizal seedlings, along with the competition between arbuscular mycorrhizal fungi and the pathogen for root colonization and access to energy resources, are among the key mechanisms that improve pistachio seedlings tolerance to Armillaria root rot under both saline and non-saline conditions. The results of this study can serve as an effective approach to mitigating the detrimental effects of salinity stress and enhancing pistachio seedlings tolerance to Armillaria root rot.

  Author contribution

All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.

Data availability

The data will be made available on request.

 Acknowledgement

This research was financially supported by the UniversityCollege of Agriculture and Natural Resources, University of Tehran. We thank University of Theran for providing research facility and support.

 Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.