Screening of Potato Lines Including Department Genetic &National Plant Gene Bank of Iran for Resistance to Early Blight (<i>Alternaria. solani</i>) Using Culture Filtrate Produced by the Fungus

Potato is a plant that can be influenced by early blight disease. Early blight is one of the most destructive plant diseases, especially in the members of solanaceae family. This disease can reduce yield. Experiment design was a factorial randomized complete design to evaluate the isolate pathogenic Alternaria solani in National Plant Gene Bank of Iran, during 2008-2009. This experiment was conducted with three replications, and the factors include test methods and three lines 9506, 10908-05 and 10908-18 with genotypes of Agria, Casmos and Desiree (susceptible) and Delta (resistant control). Analysis of variance table was based on the area under the disease progress curve, indicating the effects of the experimental methods;genotype and their interactions are significant at the 1% level. In greenhouse evaluation, the symptoms appeared on, the first day. In this method the area under the curve progression was noted in 10 times, but in vitro method, the symptoms of this evaluation appeared on the first or second day. The Evaluation was carried out after inoculation, and was noted 6 times. The results indicate that genotypes and lines are located in four different groups. In this case, line 9506 and Cosmos were quite sensitive to the surface, and Desiree, is located in a sensitive area. Line 10908-18 and Agria, located approximately at the level of resistance, and line 10908-05 and Delta, have been resistant surface.

Assessment on early blight of potato in order to compare the two methods<i>in vitro </i>using pathogenic fungi <i>Alternaria solani</i>

Potato (Solanum tuberosum) early blight, caused by Alternaria solani is one of the most destructive fungal foliar diseases. This research was done in order to study methods comparison of evaluation by culture filtrate of A. solani in in vitro condition for selecting resistance cultivars to early blight. Plantlets of potato viruse free were obtained from the National plant gene bank of Iran, and were inoculated in vitro methods with a culture filtrate of A. solani. In in vitro selection by droplet of culture filtrate method, leaflet received a 10 μl droplet of the A. solani culture filtrate and in in vitro selection by direct using of culture filtrate method, plantlets were placed in test tubes that include 5 μl A. solani culture filtrate. The experimental design was factorial on basis of completely randomized design (CRD) with two factors, three replications and six genotypes. During droplet method assay, the A. solani symptoms appeared 1 - 2 days until 6 days and during direct method they appeared 2 - 3 days until 6 days. The AUDPC values were submitted to the analysis of varience (ANOVA) and AUDPC means were compared by using Duncan test (α = 0.01%). In each method, significant difference among potato cultivars was observed for disease to early blight (p < 0.01). Results show that casmos cultivar is susceptible for resistance to early blight and in vitro methods experiment had the same result.

<i>In vitro</i>and greenhouse evaluation for resistance to early blight of potato isolated from <i>Alternaria alternata</i>

Early blight of potato is caused by the fungus Alternaria alternata, one of the most destructive foliar diseases, especially in hot climates under irrigation. In this study, the virus free potato seedlings were obtained from the National Plant Gene Bank of Iran and were inoculated in vitro with a culture filtrate of A. alternate. The leaflets received a 1000-μl droplet of the A. alternata culture filtrate and were inoculated by spraying with a suspension of 105 conidia/ml of isolate A. alternata in the greenhouse method. The experimental design was a completely randomized design (CRD) with three replications and seven genotypes, which have been infected with the two leaves of each iteration. In vitro selection of fungal isolates of A. alternata, chlorotic and necrotic symptoms began 1 to 2 days after inoculation, but the assessment of greenhouse symptoms appeared 6-10 days after inoculation. The area under the disease progress curve values were presented by analysis of variance (ANOVA), and they were compared using Duncan’s test (a = 0.01%). In both methods, there was a significant difference between the potato genotypes (P In vitro selection and evaluation greenhouse, Casmos were resistant to at least figure and Marfona genotype had the highest resistance.