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Rice sheath blight and its causal agent Rhizoctonia solani AG-1 IA are associated with intensive and high input production systems. To our knowledge, resistant varieties have not been introduced for this disease, thus good crop management is expected to be among viable disease control methods. The aims of the present study were to determine the effect of different rates of nitrogen fertilizer, planting spaces and inoculum densities on sheath blight incidence and severity, including grain yield loss. Additionally we aimed to identify those developmental stages that are more susceptible to the disease. Field experiments were conducted over two consecutive years, in 2017 and 2018 in the Guilan province of Iran. Results indicated that higher N rates, denser planting and higher initial inoculum density resulted in greater disease development. Among five different growth stages, inoculation of plants at booting and flowering stages, resulted in maximum disease severity and grain yield loss. Taken together, reasonable use of nitrogen fertilizer, optimum planting space and reduced inoculum density obtained by spraying fungicide at the booting and flowering stages of rice are suggested as the best options to control sheath blight epidemics in rice.

An experiment was conducted in order to investigate the effects of exogenous polyamines (PAs) on the development of mycorrhizae in roots, nutrient uptake and vegetative and reproductive growth ofFreesia hybrida‘Golden Wave’. Corms of freesia were inoculated withRhizophagus intraradicesat sowing time and treated once a week by one of three PAs, putrescine (Put), spermidine or spermine, in concentrations of 0.05 and 0.1 mM each as foliar application or soil drench. Application of PAs, especially as soil drench, increased mycorrhizal colonization as well as the growth and development of inoculated plants. Among the three PAs, Put in 0.1 mM concentration was the most effective in increasing colonization, enhancing floral stem length and diameter, floral spike length, floret number on main and lateral spikes and increasing corm and cormlet weight, corm diameter and cormlet number. Sole application of arbuscular mycorrhizal fungi had no significant effect on the flowering time but soil drench with 0.1 mM Put accelerated flowering by about 17 days. Application of PAs elevated leaves N, P, K, Mg, Fe and Zn and corms’ P, K, Ca, Fe and Zn concentration of inoculated plants. Our results suggest that soil drench application of PAs, especially Put, positively influenced mycorrhizal inoculation and nutrient uptake, which leads to improving growth, flower and corm production and quality of mycorrhizal plants of freesia.

Genetic variation in 60 isolates of Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial blight disease, investigated using random amplifi ed polymorphic DNA (RAPD) markers. All of 60 strains isolated and characterized through 2006-2008 in Guilan province. Three populations: a) isolates from nursery, b) isolates from fi eld, and c) isolates from panicle studied. Eight decamer primers of RAPD amplifi ed 187 polymorphic bands. The largest and smallest fragments generated by 80.7 and OPA10 primers, respectively. The minimum amount of polymorphic information content was related to OPA12 primer (0.36) and the maximum amount of that was related to OPA10 primer (0.44). Analysis of molecular variance (AMOVA) of data from RAPD analysis showed that the genetic variation within Xoo populations was greater than between populations. The similarity matrix conducted by Simple Matching coeffi cient and cluster analysis made by unweighted pair group method (UPGMA) with NTSYS-pc soft ware. At a similarity index of 0.6 the isolates were grouped into 3 clusters. These results revealed that the RAPD markers used in this study could differentiate nursery and fi eld isolates from each other.

The adult‐plant resistance of wheat to infection by Puccinia striiformis f. sp. tritici was studied. The expression of resistance controlled by the resistance factor YR 14, in the spring wheat cvs Solitaire and Wembley, and the durable resistance of cv. Hybride de Bersee, were investigated over a range of plant ages. Neither resistance type affected urediniospore germination, but both involved increased latent periods at adult plant stages. Assessment of infection type suggested that the durable resistance of Hybride de Bersee may be recognized at earlier plant growth stages than the resistance attributable to the factor YR 14. Zusammenfassung Die Ausprägung der Resistenz ausgewachsenen Weizens gegen Puccinia striiformis Untersucht wurde die Resistenz ausgewachsenen Weizens gegen eine Puccinia striiformis f. sp. tritici‐Infektion. Die Ausprägung einer Resistenz, die durch den Resistenzfaktor YR 14 bei den Sommerweizensorten Solitaire und Wembley kontrolliert wird, und die dauerhafte Resistenz der Sorte Hybride Bersée de, wurde bei unterschiedlichem Pflanzenalter ermittelt. Die Urediniosporen‐keimung wurde durch beide Resistenztypen nicht beeinflußt, aber bei erwachsenen Pflanzen wurden verlängerte Latentperioden beobachtet. Eine Beurteilung des Infektionstyps deutete darauf hin, daß die dauerhafte Resistenz der Sorte Hybride de Bersée in jüngeren Wachstumsstadien erkannt werden kann als die Resistenz durch den Faktor YR 14.

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Different viral diseases infect common bean crops in Iran. A total of 248 symptomatic samples were collected from common bean fields throughout main growing fields of Guilan province in Iran during the summer of 2006. Eight viruses were detected using double antibody-sandwich -enzyme-linked immunosorbent assay (DAS-ELISA). Bean common mosaic virus -BCMV (1%), Bean leaf roll virus -BLRV (9%), Cowpea mild mottle virus -CpMMV (6%), Southern bean mosaic virus -SBMV (3%), Cucumber mosaic virus -CMV (15%), Bean golden mosaic virus -BGMV (2%), Bean common mosaic necrosis virus -BCMNV (1%) and Bean yellow mosaic virus -BYMV (1%) were detected. Comparatively CMV (15%) was found to be more prevalent in Guilan province. Multiple infections of viruses were recorded in many samples. Weed species belonging to Chenopodiaceae, Solanaceae, Malvaceae and Amaranthaceae families were also found to be infected with the viruses.