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Three Trichoderma harzianum isolates, were evaluated for their antagonistic effect on Rosellinia necatrix causal agent of white root rot (WRT). According to in vitro evaluations, T. harzianum T20A isolate showed the most pathogen growth inhibition. The inoculum of T20A isolate was applied to control WRT disease on four commercial apple rootstocks: Malling (M7, M25) and Malling Merton (MM111, MM106) in greenhouse experiments. Root rot and leaf fall indices were measured 70 days after pathogen inoculation. The biocontrol agent had a significant effect (p < 0.01) on the reduction of pathogen indices but the effect of rootstocks was not significant. Root rot reduction on MM111, MM106, M25 and M7 rootstocks were 63.84%, 61.13%, 28.63% and 17.47%, respectively. The antagonist also caused reduction of leaf drop symptom on MM106, M7, MM111 and M25 infected apple rootstocks by 57.4%, 56.06%, 44.09% and 40.24%, respectively. Disease indices were also measured for fungicide treatment and the results were compared with disease indices in antagonist treatments. The most biological control was observed on MM111 (63.84%) and MM106 (57.4%) according to the reduction in root rot and leaf drop, respectively. The reactions of apple rootstocks to WRT were also evaluated. The results showed that all the rootstocks were susceptible to WRT in the greenhouse condition. The MM106 rootstock which showed 100% root rot and 78% leaf drop was the most susceptible and M7with 43.5% root rot and 84.56 leaf drop was the least susceptible in our experiment. This was the first study of reaction and biocontrol of white root rot disease on apple commercial rootstocks in Iran and the results suggest a better insight to disease management either by integrating resistance and biocontrol measures or replacing chemical control by antagonist application to soil.

Anthracnose disease caused by Ophiognomonia leptostyla, is the most important and widespread fungal disease on Juglans regia. Walnut disease symptomatic samples were collected from different provinces of Iran, during 2015–2016. Fungal isolates were identified based on ITS-rDNA sequence data. Variance analysis of colony growth rate (mm/day) and acervulus density on medium, was significant. Acervulus density on medium was strongly correlated with colony growth rate. The Max acervulus density was 60% and > 80% for Hamedan and Mazandaran isolates respectively. The virulence of six selected isolates was examined on cv. Chandler. Virulence indices including spot diameter, disease severity, spot area average and logistic infection rate except spot number index, could successfully detect significant differences among isolates. SA-SE1 isolate from Mazandaran showed significantly the most virulence indices: disease severity (%), spot area and logistic infection rate. For the other five isolates, four significant levels in all virulence indices were observed. In summary after this isolate, other isolates including TA-ZY21, LA-SY21, U94-SR1, HA-GH22 and MA-K1 were placed in the next steps of virulence ranking. There was insignificant correlation between colony growth rate and disease severity. However, the acervulus density and disease severity were significantly correlated implying the importance of acervular conidial inoculum in secondary disease cycle progress. Disease severity was strongly correlated with number of spots, spot diameter and logistic infection rate. Disease severity was also negatively correlated with Mid-time (time to progress 50%). Moreover, there was positive relationship between logistic infection rate and three traits: number of spots, spot diameter and spot area average. This study was the first of the disease virulence components on cv. Chandler in Iran.

Spectroscopy in visible and part of near infrared region was assessed as a non-destructive technique for the detection of plants infected with Potato virus Y (PVY). The aim of our research was to recognize spectral signatures that indicate PVY infected plants. In this assay, we studied spectral reflectance of potato leaves showing different PVY symptoms in cultivars Agria and Milva. Virus titer of leaves that showed different disease symptoms, were estimated using enzyme-linked immune sorbent assay. The means of spectral data obtained from different leaves in each experimental plant were used for spectral analysis. Analyses showed that spectral region in 900-1100nm was markedly sensitive to the PVY infection and could be useful for developing a good spectral signature for detection of the infection. Based on the X loading weights obtained from principal component analysis (PCA), sensitive wavelengths were screened, some wavelengths in this region have most positive or negative loading and based on linear discriminant analysis, they could discriminate infection status with high accuracy. The reflectance variation in this region is related to changes in cell structure and water activity due to viral infection. Results indicate that spectroscopy has a suitable potential to detect virus-infected plants; which could be further developed for more accurate potato field inspection aimed at controlling the spread of viral infection.

A survey was carried out in citrus nurseries in Mazandaran and Kerman provinces as the major citrus growing regions of Iran. Different varieties of orange and tangerine with abnormal symptoms were examined for the occurrence of Candidatus Liberobacter asiaticus, Spiroplasma citri and phytoplasma as the most important vascular limited pathogens in citrus. By visual inspection and molecular examination of 360 samples for the presence of fastidious prokaryotes only an occasional occurrence of phytoplasma and Spiroplasma citri were detected, using phytoplasma universal primer pairs P1/P7 and fU5/rU3 (in single tube nested PCR assay) and Spiroplasma specific primers P89-r/f and P58-6f/4r. PCR products of phytoplasmas were digested with MseI, AluI, BamHI and TaqI restriction enzymes and the digestion results showed phytoplasma related to aster yellows phytoplasma group. No amplicon was obtained for Candidatus Liberobacter asiaticus. The findings suggest when pathogen’s titer is low; symptoms of vascular limited diseases are almost confused with disorder and deficiency signs. So for sanitary selection and certification program, use of sensitive detection methods is recommended. Multiplex PCR assay used in this study successfully detected Candidatus Liberibacter asiaticus, Spiroplasma citri and phytoplasma in one reaction and is suggested for health certification programs.