Journal of Applied Research in Plant Protection
Year:2021 | Volume:9 | Issue:4|Papers Count:8

Poplar leaf spot disease, caused by Sphaerulina frondicola (syn: Septoria populi), is one of the important and serious diseases of populus trees, which causes significant loss on this host. Considering the importance of this disease, in the present study, the genetic diversity of 138 S. frondicola isolates obtained from populus trees in different regions of East and West Azarbaijan Provinces was analysed using RAPD and ISSR molecular markers. The results indicated considerable genetic variation amongst the studied populations. The mean genetic diversity for all of the populations using data from all primers was 0. 199 at the probability level of 0. 001. The lowest genetic differentiation was observed between Hurand and Kaleyber populations (0. 352) with the highest gene flow (54. 956) and the highest genetic differentiation was observed between Khoy and Bostanabad populations (0. 516) with the lowest gene flow (0. 468) which is consistent with geographical distance. Based on Nei's genetic distance, the Bostanabad population showed the highest genetic distance from the other six populations. Haplotype analysis clustered the isolates from a single tree or even single spot in different groups, suggesting the existence of high genetic diversity in a small scale. Overall, the existence of different haplotypes and distribution of genetic diversity in a small scale observed in this study, suggests occurrence of regular sexual cycle in S. frondicola populations and highlights the role of airborne ascospores as primary inoculum source in disease cycle.

The sunflower lace bug Galeatus scrophicus has yet been recorded in Iran on tamarisk, sunflower and chrysanthemum. In the present study, its morphology, spatial distribution pattern of nymphs and symptoms of damage were investigated. The insect has five instars and average body length in first to fifth instars and male and female adults were 0. 54 ± 0. 03, 0. 76 ± 0. 06, 1. 01 ± 0. 06, 1. 23 ± 0. 07, 1. 76 ± 0. 05, 2. 72 ± 0. 11 and 2. 98 ± 0. 10 mm, respectively. Nymphs have thorn-like structures on their bodies which become longer by introducing to the next instar. At fifth instars, bulb-like structures similar to those of adults appear on body. Larger size of hood in comparison to the posterior pronotal bulb and five cells in paranotal process are two characters of adults of this species. Average body length in male and female adults were 2. 72 ± 0. 11 and 2. 98 ± 0. 10 mm, respectively. On sunflower and chrysanthemum, nymphs and adults caused damage just on upper and lower leaf surfaces (on sunflower also on upper and lower surfaces of involucral bracts). Damage on both upper and lower surfaces began mainly at leaf margin (sometimes at the adjacent of midrib) and then extended to the inner parts of lamina. Faeces of nymphs and adults were visible individually and at high numbers at feeding sites as shiny small black spots. According to the results, the spatial distribution of nymphs on sunflower by using five distribution indices was random. For determination of spatial distribution parameters, Taylor's model was more adequate than Iwao's model.

Wheat yellow rust, caused by Puccinia striiformis f. sp. titici, is one of the most important and most destructive diseases of wheat in many parts of Iran, which decreases crop yield in epidemic years. Host resistance is the most economical method for the management of yellow rust and partial resistance (a type of quantitative resistance), proven to be more durable than other types of resistances. In this study, partial resistance parameters including coefficient of infection (CI), final disease severity (FDS), relative area under disease progress curve (rAUDPC) and apparent infection rate (r) were evaluated in a set of twenty-four wheat genotypes along with susceptible control during two crop years from 2015 to 2016. The research was conducted at Allarough Agricultural Research Station in Ardabil, under natural and artificial inoculation conditions. Artificial infection of genotypes was performed using the yellow rust race population having virulence for Yr2, Yr6, Yr7, Yr9, Yr17, Yr22, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, Yr26, Yr27, Yr21, Yr21, Yr31, Yr32 and YrSU resistance genes. Seedling response was also evaluated under field conditions. The evaluation of resistance parameters showed that six lines were resistant at both seedling and adult plant stages. Eleven lines showed resistance reaction at seedling stage, but moderate or susceptible reactions at adult plant stage. Seven lines (entries; 1, 4, 7, 8, 9, 16, 22) were susceptible at the seedling and had moderate (MR, M or MS) reactions at adult plant stages. Therefore, these lines having low values of different resistance parameters are likely to have varying degrees of partial resistance or high temperature adult plant resistance (a type of non-specific or durable resistance). Cluster analysis based on the reaction of seedling and adult plant, divided the lines into different groups, which also indicated a high diversity of lines in response to yellow rust disease.

Grape leafhopper, Arboridia kermanshah (Hemiptera: Cicadellidae) is one of the important pests of grapevine in Iran. In this research, the spatial distribution of A. kermanshah immature stages was investigated in a vineyard of the Kermanshah region, during 2017 and 2018. Grape leaf selected as sampling unit and sampling process carried out every week. The spatial distribution of eggs and immature stages of this pest calculated using: Index of dispersion, Morisita, Lloyd’ s mean crowding index, Iwao’ s patchiness regression and Taylor’ s power law Indexes. Most used methods revealed an aggregated spatial distribution for the pest (b > 1). According to the Iwao’ s method in first sampling year, regression for 4 th and 5 th nymphal instars, was not significant (P-value > 0. 05). In Taylor method for both sampling years and Iwao’ s method for second sampling year, distribution calculated random for 4 th and 5 th nymphal stages. Also, using the Morisita’ s index in both sampling seasons and most (10) sampling dates, for the 4 th and 5 th nymphal stages, random distribution calculated. In both sampling seasons, Taylor’ s power law method found to be more accurate than other methods in determination of the spatial distribution for this pest. Additionally, the lowest optimum sample sizes calculated using Taylor’ s coefficients that were more affordable in comparison with other methods. Knowledge of the spatial distribution of this pest can be useful in designation of suitable sampling programs. Estimation of optimum sample sizes can also be useful in decreasing of sampling costs in both research and management programs.

Control of bacterial diseases is one of the problems in agricultural products, specially greenhouses. In this study, the effect of compost and vermicompost fertilizers and their tea on tomato plants infected with bacterial vascular wilt caused by Ralstonia solanacearum in greenhouse conditions was investigated based on a factorial experiment with a completely randomized design including four types of compost fertilizers, in four concentrations (zero, 20, 30 and 40% by volume). Bacterial suspension with concentration of 10 8 CFU / mL was added to pot soil at two to three leaf stage of seedlings. The percentage of reduction on disease incidence and growth index changes in treatments were compared. The results showed that most of the treatments inhibited the disease compared to the control inoculated with bacteria, but the highest rate of disease control was obtained in treatments containing vermicompost with a concentration of 40 and 30% by volume, respectively 66. 67% and 60. 0%. In the substrate containing 30% by volume of vermicompost tea, the severity of disease decreased by 53. 33%. In plants inoculated with bacteria, the best growth indices were obtained in substrates containing vermicompost, compost and vermicompost tea with a concentration of 40% and also compost tea with a concentration of 30%.

Canola is an important oilseed crop in the world. Cabbage aphid, Brevicoryne brassicae is one of the most important pests of canola crop in Iran. In this study, the effect of chemical control of cabbage aphid was investigated in autumn and spring on Hyola 401 cultivar. For this purpose, spring and autumn sprayings with imidacloprid and pirimicarb at 1/1000 concentrations and insecticidal soap at 2. 5% concentration were assessed using a randomized complete block design. The experiments were conducted during two growing seasons, 2011 and 2012 in Qazvin province. The results showed that, both autumn and spring spraying is necessary for pest control. Autumn and spring sprayings with imidacloprid caused 99. 5 ± 0. 4%, 94. 5 ± 2. 4% and 95. 4. 1 ± 1. 0% mortality in 2011 and 99. 1 ± 0. 5, 86. 9 ± 2. 7 and 93. 1 ± 5. 5% mortality in 2012, three, seven and 15 days after treatment, respectively. Highest yield achieved at imidacloprid treatment and was 3533. 00 kg/ ha. If not controlled, the damage would be 66. 18, 69. 35 and 78. 0% at spring, autumn and spring-autumn treated plots.

Tobacco is one of the most important industrial and economic plants in many countries of the world which is cultivated mainly for harvesting and collecting its leaves. In order to study the response of 92 oriental tobacco genotypes to broomrape stress, an experiment was conducted in a randomized complete block design with three replications under normal (without broomrape) and broomrape stress conditions during 2007 and 2008 cropping seasons. Nine stress tolerance indices including tolerance index (TOL), relative stress index (RSI), mean productivity (MP), harmonic mean (HM), yield stability index (YSI), geometric mean productivity (GMP), stress susceptibility index (SSI), stress tolerance index (STI) and yield index (YI) were calculated based on leaf dry weight (yield) under normal (Yp) and broomrape stress conditions (Ys). Genotypes 24, 39 and 40 had the highest mean yield in normal and broomrape stress conditions. Yield value in stress (Ys) and non-stress (Yp) conditions were significantly and positively correlated with MP, HM, GMP, STI and YI indices. Using the ranking method, genotypes 40, 10 and 45 were introduced as the most tolerant genotypes to broomrape stress. Based on the results of biplot, genotypes 40, 39, 24, 19 and 4 were identified as high yielding and tolerant genotypes and genotypes 70, 69, 72, 67, 78, 71 and 8 as the most sensitive genotypes to broomrape stress. Grouping of genotypes by Ward method also classified high yielding and stress tolerant genotypes including genotypes 40, 39, 24, 19 and 4 in one group. Susceptible and low yield genotypes under stress and normal conditions including genotypes 70 and 69 were classified in the other group. Due to high diversity among the studied genotypes in view of response to broomrape stress, it is possible to select appropriate parents for breeding programs, produce diverse populations for identifying genetic loci controlling broomrape stress tolerance and study changes in the expression of tolerance genes.

Stem rust or black rust of wheat caused by Puccinia graminis f. sp. tritici (Pgt) is one of the most important and devastating wheat diseases, worldwide. Pgt possesses a high potential of genetic recombination through sexual reproduction on intermediate host which could lead to the production of new races with various virulence patterns. TTRTF, one of the novel and virulent races of Pgt, has been present in Georgia, USA since 2014; however, it was officially reported in 2016 following a widespread outbreak of stem rust on durum wheat in Sicily, Italy (Patpour et al. 2018). This race was observed in Egypt in 2016, and reported from Hungry, Egypt and Eritrea in 2017, 2018 and 2020, respectively (Patpour et al. 2020). In this study, 150 stem rust samples were collected from infected wheat fields in different regions of Iran during 2014 to 2019. Race analysis of single-pustuled isolates was carried out using 20 North American differential wheat genotypes (obtained from CIMMYT) as well as a set of 45 supplementary differential genotypes (obtained from ICARDA) based on Jin et al. (2008) method. Infection types of differential genotypes were recorded based on modified 0-4 scale of McIntosh et al. (1995) at 14 dpi. Results revealed high pathotypic (race) diversity among collected Pgt isolates. Race analysis of isolates from Oshnavieh region, West Azerbaijan province led to identification of the race TTRTF from northwest of Iran. Inoculation of wheat genotypes carrying the resistance genes Sr5, Sr6, Sr7a, Sr7b, Sr8a, Sr8b, Sr9a, Sr9b, Sr9d, Sr9e, Sr9g, Sr10, Sr11, Sr12, Sr13, Sr14, Sr15, Sr16, Sr17, Sr18, Sr19, Sr20, Sr21, Sr23, Sr28, Sr29, Sr34, Sr35, Sr36, Sr37, Sr38, SrTmp and SrMcn revealed susceptible reaction to TTRTF. Contrarily, wheat genotypes carrying the resistance genes Sr22, Sr24, Sr25, Sr26, Sr27, Sr30, Sr31, Sr32, Sr33, Sr39 and Sr40 were evaluated as resistant to this race. However, reaction of genotypes carrying the genes Sr44, Sr45, and Sr50 (adult plant resistance genes) to TTRTF race of Pgt has been reported as susceptible (Patpour et al. 2020). Some of the Sr resistance genes that displayed effectiveness against many Iranian P. graminis f. sp. tritici races are ineffective to this race. Due to new virulence pattern, this race is assumed as a serious threat to global food security, particularly in rust suitable areas including Iran. Identification of effective sources of resistance to TTRTF, and exploiting them in wheat breeding programs could be considered as one of the main strategies in stem rust management.