مجله دانش گیاه پزشکی ایران
سال پنجاه و چهارم شماره 2 (پاییز و زمستان 1402)

Root and crown rot is a common tomato disease in the major production areas of Hormozgan province. The present study was conducted to isolate, identify, and determine the frequency of fungal agents associated with tomato root and crown rot in Hormozgan province. In total, 984 fungal isolates were obtained from tomato plants with yellowing, wilting, and root and crown rot symptoms. Identification of the isolates was done based on the morphological characteristics and the comparison of the obtained sequences of the ribosomal internal transcribed spacer region (ITS-rDNA) and parts of the translation elongation factor-1 alpha (tef1-α) gene with relevant sequences available in GenBank. According to the results, the highest frequency belonged to Fusarium oxysporum isolates (73%), and afterward to Rhizoctonia solani and F. acutatum species with eight and one percent frequencies, respectively. The results of the pathogenicity tests of the fungal species on tomato seedlings hybrid Sunseed 6189 at the stage of four true-leaves revealed that all three species were pathogenic on tomato seedlings and caused root and crown rot, yellowing, and death of the plant aerial tissues. Pathogenic isolates of F. oxysporum were identified as F. oxysporum f. sp. radicis-lycopersici using sprl-specific primers. To the best of our knowledge, this is the first report of F. oxysporum f. sp. radicis-lycopersici on tomato in Hormozgan province, and the first report of F. acutatum as tomato root and crown rot agent in the world.

Cannibalism, killing and consuming conspecific individuals is a widespread phenomenon that happens in many species. In this study we have investigated the effect of domatia on the cannibalism behavior of the Phytoseiid predatory mites, Phytoseiulus persimilis and Amblyseius swirskii, on sweet pepper leaves with and without domatia. The without-domatia leaves were prepared by banning the domatium with glue. To avoid the unwanted effect of glue, we put the same glue drops next to each domatium. The experiment about the effect of domatia on the cannibalism rate of predatory mites on detached leaf disks showed that for P. persimilis, the presence of domatia significantly reduced the cannibalism rate (P < 0.05). In contrast, when we changed the predator species to A. swirskii, no significant effect was recorded (P > 0.05). To investigate the effect of domatia on the establishment rate of the predator, we used the pair of detached leaves with and without domatia connected through a plastic bridge. The predators were released in the middle of the bridge. The results showed that in both predator species, the presence rate of female predators on patches with domatia was significantly higher in comparison with those without domatia (P < 0.05). The probable reasons for the difference in predator behavior are discussed.

Crown and root rot disease caused by Fusarium pseudograminearum is one of the growth-limiting factors in wheat cultivation. This disease is usually associated with the browning of the coleoptile, lower leaf sheaths, adjacent stems, and nodes. To deal with this disease, various strategies have been used, including the use of bacteria that increase plant growth. In this research, the bacterium Pseudomonas fluorescens strain EB298 was isolated and identified from the soil contaminated with this disease in Andimeshk city. This isolate was able to reduce the amount of plant ethylene from 30 nmol/g to 20 nmol/g. As a result of reducing the amount of ethylene, the amount of hydrogen peroxide, which was representative of active oxygen in this research, decreased from 45 M/gFWµ in the control sample to 27 M/gFWµ in the sample inoculated with bacteria. The damage caused by crown rot fungus (pathogenic intensity) was significantly reduced from grade 4 in the control to grade 2. The results of this research show that seed inoculation with P. fluorescens UTPf298 bacteria, in addition to controlling root rot disease, has reduced ethylene and hydrogen peroxide and ultimately the severity of pathogenicity in wheat. Also, this bacterium, by affecting the growth of the plant, strengthened the plant and the greenness of the wheat plant.

The mating behavior of the predatory mite Euseius scutalis (Athias-Henriot) (Acari:Phytoseidae) was studied under laboratory conditions at a constant temperature of 25 ± 1 ºC, 60 ± 5% relative humidity and photoperiod of 16: 8 h (L: D). Twenty pairs of newly emerged virgin females and unmated males were kept separately on plastic discs in Petri dishes (9 cm diameter) and their mating behavior was observed continuously under a stereomicroscope using cold light. During mating behavior four phases were recognized. The mean time until the first contact of female and male individuals was approximately 14.4 ± 3.25 minutes (Phase 1). After the first contact the mite male moved to the top of female's dorsum and stayed there for a short time and later moved to the underneath of her in mating position (venter-to-venter position). The mean time needed for this phase was 0.17 ± 0.01 minutes (Phase 2). Then the female walked for mean of 1.09 ± 0.03 minutes in venter-to-venter position (Phase 3). Subsequently the female mite remained still in the mating position for mean of 16.8 ± 0.78 minutes during which probably the sperm transferred from male to female (Phase 4). In addition our results indicated that no changes were observed in the spermathecae of virgin females; after mating most of the females had one spermatophore in one spermatheca while in few of tested females one spermatophore was found in both spermathecae.