نشریه پژوهش های کاربردی در گیاه پزشکی
سال سیزدهم شماره 3 (پاییز 1403)

The pathogen, Pythium aphanidermatum is one of the causal agents of sugar beet root rot in Iran. In order to evaluate the reaction of cultivars to the pathogen, at first, the screening method of evaluation was optimized. Then, a number of 24 cultivars that are commonly cultivated in Iran were evaluated against the pathogen. Three different evaluation methods in the greenhouse including grass leaf suspension, oospore suspension, and grass leaf suspension using through making wounds on the roots were compared with each other. A number of 12 cultivars were inoculated with these three inoculation methods. The results showed that positive and significant correlation of the three methods with each other. Then, 24 commercial sugar beet cultivars were evaluated with grass leaf suspension method under the greenhouse conditions. Based on the results of the evaluation of the 24 commercial cultivars of sugar beet and the comparison of the disease index of Pythium root rot based on Duncan's multi-range test, Ivano, Boomrang, Flores and Tous had the lowest rot index among the cultivars with the average index of 2.58, 2.65, 2.72 and 2.75 respectively and were introduced as resistant cultivars to the disease. Cultivars Jolgeh, Rasool, Shirin and Jam were categorized as susceptible.

Spatial distribution of plum bud gall mite, Acalitus phloeocoptes and its seasonal fluctuations were studied in a plum orchard, at the Miandoab region, West Azerbaijan province during 2021 and 2022. Five samples in the geographical main directions and centre of the tree were randomly selected per sampling dates. A branch was selected as a sampling unit, and sampling with a total number of one hundred branches of twenty trees was performed. The results showed that gall density was not significantly affected by the geographical directions (P > 0.05) and they were regularly distributed in all parts of the plum trees. Gall density at the first sampling year was significantly more than the second year. The spatial distribution pattern of bud galls using Taylor's power law and Iwao's patchiness regression, index of dispersion and Lloyd's mean crowding was regular at first sampling year, while using Taylor's method and Iwao's patchiness regression was random and in the second year of mite activity was regular using other methods. Moreover, the results of linear regression revealed that there was significant relationship between the temperature and relative humidity with the number of galls, resulting gall density is dependent on the environmental conditions. Density and spatial distribution of bud galls, identified in this research, are among the key elements in pest management programs and should be considered in samplings.

Plant probiotic bacteria have been found to induce systemic plant defense and affect the interactions between plants and insects across different trophic levels. In this research, the effect of a probiotic bacterium, Bacillus subtilis (strain S) on life table parameters of Brevicoryne brassicae, and its parasitoid wasp, Diaeretiella rapae, on canola was investigated. The results showed that the S strain significantly reduced the intrinsic rate of increase (r) of the cabbage aphid. The values of the intrinsic rate of increase (r) were 0.302 ± 0.012 and 0.237 ± 0.007 (day-1) for control and plant probiotic bacteria-treatments, respectively, while, net reproductive rates (R0) were 16.60 ± 1.90, and 33.71 ± 2.60 (offspring/individual), respectively. The study on the biology of parasitoid wasp showed no significant differences in various life table parameters, except for the mean generation time (T) between control and bacteria-treatments. Additionally, the gas exchange was measured on the control and canola treated with the various strains of B. sabtilis including S, GBO3, INR7, AS, and BS. The results indicated that the highest and lowest photosynthetic rates were calculated in S and AS, with rates of 21.66 and 5.91 µmol (Co2)/m2/S, respectively. Based on our findings, the S strain of B. subtilis, by reducing the aphid's capacity to increase its population, can be used as an effective agent in the integrated management of the cabbage aphid.

Saffron (Crocus sativus) is a high-value perennial plant cultivated widely in Iran as a spice and medicinal plant. Several pathogens including viruses can infect saffron and decrease its quality and quantity. Precise and reliable detection is a critical aspect of disease management in viral diseases because of the lack of commercially available chemicals against plant viruses. Nowadays, high throughput sequencing (HTS) has been considered as a routine technology for detection of known and novel viruses in commercial plants. In this study, using HTS data, saffron latent virus (SaLV) and prunus virus T (PrVT) were identified in transcriptomic data of stigma of saffron and near complete genome of these viruses were obtained. The near complete genome of SaLV isolate had 98.3% nucleotide sequence identity with the only available isolate in GenBank. The complete genome of saffron isolate of PrVT shared 42.9 (potato virus T isolate Peru) – 76.9 % (olive virus T isolate GR168) nucleotide sequence identity with those of tepoviruses available in GenBank. In a phylogenetic tree, the PrVT isolate clustered with two Greece OlVT isolates along with an isolate of PrVT. To the best of our knowledge, this is the first report of PrVT infection in saffron worldwide.

Over the past two decades, biological control of wheat septoria tritici blotch (STB) caused by Zymoseptoria tritici has been evaluated as a reliable and safe alternative or complement to chemical control. The genus Trichoderma includes several biocontrol agents (BCAs) widely used worldwide against plant diseases. Besides direct control of plant pathogens, Trichoderma spp as BCAs provide numerous other beneficial features for their plant hosts. The current study aimed to assess the potential biocontrol ability of several antagonistic Trichoderma isolates with endophytic potential on STB reduction in wheat cultivar Tirgan under greenhouse conditions. The antagonists were used as a seed-coated treatment at the sowing time and sprayed on the plants 72 h before Z. tritici IPO323 inoculation. STB severity was calculated 21 days after the pathogen inoculation. The biocontrol isolates significantly (α = 0.01) reduced the disease severity on cv. Tirgan. T. harzianum AS12-2 provided the highest average percentage of STB inhibition in both application methods. Application of T. harzianum AS12-2 led to a reduction in the percentage of leaf area covered by lesions (PLACL) and the percentage of leaf area covered by pycnidia (PLACP) by 80.12% and 77.71%, respectively. Trichoderma biocontrol isolates could be considered safe and reliable alternatives/complements for sustainable agriculture in integrated management programs of wheat STB.

The diversity of weed communities and their differences in response to herbicides have made mixed herbicides application inevitable. In this research, the efficacy of transplanted rice herbicides in controlling weeds in rice direct seeded rice was investigated. Comparison of the efficiency of premixed herbicide pretilachlor + pyribenzoxim (solito, EC 32%, 480 g ai ha-1) in a pot experiment with the common herbicides bispyribac-sodium (two formulations SC40%, SC10%), pyribenzoxim and bentazone + MCPA showed that the premixed herbicide provided similar control of barnyardgrass and bulrush as did common herbicides. Field experiment treatments included bentazone + MCPA + pendimethalin, bentazone + MCPA + thiobencarb, bispyribac-sodium + pendimethalin, bispyribac-sodium + thiobencarb, pretilachlor + bensulfuron-methyl and doses of 0, 50, 100, 150 and 200% of pretilachlor + pyribenzoxim mixed with thiobencarb. The results showed that pretilachlor + pyribenzoxim did not show any phytotoxicity symptoms on rice up to twice the recommended dose. Application of the recommended dose of pretilachlor + pyribenzoxim + thiobencarb provided 90% and 70% control of barnyardgrass (Echinochloa crus-galli) and bulrush (Bolboschoenus planiculmis) respectively. The lowest and highest yield of paddy was 517 and 5495 kg/ha, respectively, which was recorded in the weedy and bispyribac-sodium + thiobencarb treatments. The yield of paddy at the recommended and twice the recommended dose of pretilachlor + pyribenzoxim was statistically the same 4761 and 4827 kg/ha, respectively. Overall, the results of this research indicated that the application of pretilachlor + pyribenzoxim (480 g ai ha-1) after soil-applied thiobencarb (2750 g ai ha-1) provided very good control on the important weeds of rice in direct cultivation on wet bed and can be introduced as a suitable alternative to common herbicides.

To investigate the effect of black rust disease (Puccinia graminis f. sp. tritici) on wheat yield and its components and to identify genetic resources resistant to this disease, 24 wheat genotypes were evaluated in 2020-2021 at the East Azarbaijan Research Center for Agriculture and Natural Resources. The evaluation was conducted under both infected and non-infected conditions with the native race TKTTF of the black rust, using a randomized complete block design with three replications. Talcum powder was used for inoculation, and after sprinkling distilled water and saltrol oil on the plants, inoculation was done using a mechanical sprinkler. The test results indicated a significant difference between the genotypes in terms of plant height, spike length, spike diameter, spike weight, number of seeds per spike, hundred seed weight, seed yield, biomass and harvest index was observed at the probability level of 1%. Additionally, the results demonstrate that pathogen infection causes a decrease in stem diameter, number of seeds per spike, hundred seed weight, seed yield, biomass and harvest index. Based on the studied traits, the Zareh and Heyran cultivars, as well as the C-98-14, C-98-13, C-98-12 and CD-94-5 lines, were identified as resistant genotypes. The genotypes were classified into four groups under infection and non-infection conditions and into three groups under medium infection conditions, based on cluster analysis and detection function analysis. The research results indicate that black rust infection has a negative impact on both the yield and its components. Additionally, the diversity between genotypes can be utilized to enhance wheat genotypes.

Wheat leaf rust caused by Puccinia triticina is the most important wheat disease in terms of its wide distribution and yield loss in the world. To investigate the virulence factors of P. triticina in Iran, the present research was carried out in several locations including Karaj, Gorgan, Sari (Ghaemshahr), Kelardasht, Ardabil, Moghan, Boroujerd, Ahvaz, Dezfoul, and Kermanshah. In this research, 39 Near isogenic lines (NILs) developed from the wheat cultivar Thatcher and each carrying a specific leaf rust resistance gene/s were examined under natural disease infection during the two years 2022-2023. At the full opening of flag leaf stage and after uniformity in disease emergence on the susceptible cultivar, disease severity and infection type were scored based on the modified Cobb scale and Rolfes et al. respectively. In this study, reactions of 50S and higher were recorded as virulence for the contaminated lines. Based on the isogenic lines reactions in different locations in 2022, no virulence was observed on Lr1, Lr2a, Lr3ka, Lr10, Lr11, Lr12, Lr14b, Lr17, Lr18, Lr19, Lr20, Lr21, Lr22a, Lr29, Lr32, Lr33, Lr34 and the gene Lr37 and in 2023 no virulence was observed on Lr9, Lr17, Lr18, Lr19, Lr22a, Lr29 and the Lr30. Based on two-year results of isogenic lines in different locations, no virulence was observed on the genes Lr17, Lr18, Lr19, Lr22a and Lr29 gene combination in the study areas during the two years of isogenic lines and then identified as effective genes for wheat rust disease. Virulence was observed on plants carrying other resistance gene/s, at least in one location tested, indicating ineffectiveness of the gene/s to leaf rust in that location.