نشریه دانش بیماری شناسی گیاهی
سال دوازدهم شماره 2 (پیاپی 24، بهار و تابستان 1402)

Early blight caused by Alternaria species is one of the major tomato diseases worldwide, causing losses of up to 86% of yield. Identifying and cultivating resistant varieties is the best method for disease management. Considering the prevalence and importance of diseases in Iran, this study was conducted to identify resistant cultivars among 15 available varieties.

In Kohgiluyeh and Boyer-Ahmad province in southwestern Iran, a severely affected tomato field by the disease was visited and samples of the diseased plants were taken. The pathogenic fungus was isolated on potato dextrose agar medium from the diseased tissues of the plant after their surface disinfection and after its purification by the single spore method and its morphological properties were examined and measured. The collected data were compared with the descriptions of Alternaria species and based on that, the pathogen was identified. Seedlings of 15 tomato varieties were inoculated with a conidia suspension at the 4-leaf stage in a completely randomized statistical design and maintained in a growth chamber with a temperature of 28oC, relative humidity of 90%, and a photoperiod of 16 hours of light and eight hours of darkness. Eighteen days after inoculation, the response of each cultivar to the disease was determined by calculating the percentage of infected leaves as well as the number and size of spots, and the disease index.

Alternaria alternata has been identified as the cause of early blight in tomatoes in this region. Varieties 10552, King Stone, Super Chief and Ventero with minimal symptoms were scored as resistant; 4129, 3725, 4224, Retino, Aras, Flat 111 and Super Pooya as semi-resistant and 7806, Early Pooya, 11057 and CH Pooya were known to be susceptible to the disease.

Cultivation of resistant or semi-resistant varieties can be recommended for disease control. The occurrence of tomato blight disease caused by A. alternata is reporting here for the first time from the region.

Cucumber mosaic virus (CMV) is one of the most important pathogenic cucurbit viruses. Identifying and growing resistant or tolerant varieties is the best method for disease control. The present study was conducted to investigate the response of four pumpkin varieties to CMV by assessing the expression of genes involved in resistance (PAL, PR2).

Forty samples of pumpkin leaves with suspected disease were collected from the farms in northwestern Iran and analyzed using the TAS-ELISA test. To study the response of the four pumpkin varieties Asma, Pars, Prof and PS grown in this region, a CMV isolate was inoculated into the plants in a greenhouse experiment after its biological purification. TAS-ELISA and semi-quantitative (Sq) RT-PCR tests were used to examine the virus concentration in pumpkin varieties. The disease severity index was evaluated 30 days after inoculation. The expression level of PAL and PR2 genes was also checked by quantitative real-time PCR technique.

Of the 40 samples, 16 samples were infected with CMV. The study of virus titer revealed that the virus concentration and disease severity index were higher in Pars and Proof varieties than in PS and Asma varieties. The expression of PAL and PR2 genes was increased in all varieties compared to control but was higher in PS cultivar followed by Asma.

PS and Asma varieties have higher CMV tolerance and their wider cultivation is recommended for disease control.

Root-knot nematodes damage is one of the major problems in kiwifruit production in northern Iran. This research was carried out to investigate the possibility of using dried leaves of four plants to manage kiwifruit root-knot nematode.

The soil and roots of diseased kiwifruit from the gardens of Rudsar City, Gilan Province, Iran were sampled and their root knot nematode was purified using the single egg mass method on the early Urbana tomato variety. The morphological characteristics of nematode second stage larvae and females were examined and nematode species were identified. By using the single egg mass technique, the necessary nematode population was reared on the early Urbana tomato. The effect of dry leaves of chrysanthemum, parsley, guava and oleander in two rates of 50 and 75 grams per kilogram of soil was evaluated in greenhouse conditions. The experiment was conducted in a completely randomized design with four replicates for each treatment on nematode-inoculated kiwi seedlings of Hayward cultivar. Nematode-related indices (number of galls, egg mass, eggs and J2s in 250 g of soil and reproductive factor) and plant growth characteristics (seedling height; root length and volume; fresh and dry weight of roots and shoots) were measured.

The root- knot nematode causing the disease in this region was identified as Meloidogyne incognita. In addition to controlling the nematode, the treatments used improved the growth of the kiwi seedlings. The results of the mean comparison of data showed that the treatment of 75 g of chrysanthemum leaves had a greater effect on reducing nematode population indices than other treatments. The next effective treatments were chrysanthemum at the rate of 50g, parsley at the rate of 75g, parsley at the rate of 50g, oleander at the rate of 75g, oleander at the rate of 50g, guava at the rate of 75g and guava at the rate of 50g, respectively. Treatment with 75 g of chrysanthemums also had the greatest effect on improving the growth rate of tomato seedlings.

Adding 75g of dry chrysanthemum leaves to each kilogram of soil will help reduce root nematode damage and improve the growth of kiwi seedlings.

In the suburban area of Rafsanjan city in Kerman Province, Iran, there are many orchards infested with plant parasitic nematodes. Therefore, it was necessary to identify the plant parasitic nematodes in the orchards of this region.

In 2018 and 2019, some soil samples were taken around the roots of apricot, peach, pomegranate, apple, cherry and persimmon trees in this area. Nematodes were extracted by two methods, tray and sieve-centrifuge, and after fixation, they were transferred to pure glycerin. Permanent slides were examined with a bright field microscope and extracted nematodes were identified using diagnostic keys and original descriptions.

Seven nematodes from the infraorder Tylenchomorpha, belonging to five families including: Tylenchidae, Pratylenchidae, Tylenchulidae, Criconematidae and Anguinidae were identified. Root-lesion nematode (Pratylenchus penetrans), pin-nematode (Paratylenchus neoamblycephalus) and Criconematid (Mesocriconema xenoplax) were the most important plant parasitic nematodes in fruit orchards of this region.

Due to the presence of some important and damaging nematodes in the orchards of Rafsanjan, it is recommended to implement appropriate management methods and monitor the population of important plant parasitic nematodes.

 Root lesions and cyst nematodes can cause serious damage and loss in vegetable and squash production. This research aimed to identify these important plant parasitic nematodes in the fields of these plants in the suburbs of Rumeshkan city, Lorestan province, Iran. 

 Forty-five soil and root samples were collected from vegetable and squash fields in the region, in 2021. The nematodes were extracted using the tray method and fixed using the modified de Grisse method and transferred to glycerol. After the permanent microscopic slides were prepared, the morphological characteristics of each nematode were examined using a bright-field microscope equipped with a digital camera and then identified using valid keys. 

The lesion nematodes were identified as Pratylenchus speijeri, P. neglectus and P. thornei and the cyst nematode as Heterodera schachtii. This is the first report and description of P. speijeri from Iran and also the first report of H. schachtii from lettuce in Iran. 

 Due to the presence of these important plant parasitic nematodes on these plants in this region, appropriate management practices need to be implemented.

Black scorch disease is considered one of the important and damaging diseases of date palm in many regions of the world, including Oman, Iraq, Qatar, Saudi Arabia, Kuwait, and the United Arab Emirates. The disease was first reported in Iran in 2014 from Tabas in South Khorasan Province, and in the following years, symptoms of the disease were observed scattered in Kerman, Hormozgan, Fars and Bushehr provinces. Two fungi, Thielaviopsis paradoxa and T. radicicola, are known as causal agents of the disease. Disease symptoms include tissue dieback, wilting, canopy bowing, terminal meristem rot, and tree dieback. The disease is commonly observed on trees suffering from environmental stress, particularly salt and drought stress. Although the susceptibility of different cultivars to the disease varies, the disease has been reported in 21 date palm cultivars worldwide to date. This article describes integrated disease management methods, including preventing diseases from entering the area, preventing damage to date palms, adhering to plant health principles, managing environmental stress, and proper ventilation in the grove, as well as biological and chemical control.