Assistant Professor, Seed & Plant Improvement Institute, Karaj, Iran , vrahjoo@yahoo.com
Abstract: (19967 Views)
Alfalfa downy mildew caused by Peronospora trifoliorum de Bary, is one of the factors decreases alfalfa yield. It distributes as epidemic and causes falling and yellowing the leaves in favorite conditions especially in spring and first cutting of alfalfa. In order to select alfalfa resistant ecotypes to downy mildew disease, standard greenhouse and field experiments can be used. In greenhouse tests 7-day-old seedlings are inoculated with spore suspension and after incubation period, the percentage of the symptomless seedlings is compared with resistant control as soon as disease symptoms appear. Field experiments are carried out with minimum three replications of alfalfa ecotypes in an appropriate statistical design at some locations in which natural condition for disease occurrence exists. A susceptible ecotype is used as spreader in order to help disease distribution. Resistance of ecotypes is evaluated based on percentage of the leaves infection in five different classes (1-5) scoring system. Nowadays large number of researches has been done on alfalfa resistance to downy mildew and several resistant cultivars have been reported worldwide. For example KS224 and Saranac have been known as resistant cultivars to downy mildew. Some cultivars and ecotypes such as Kiseverdai, Nikshahri, Gharghlooogh and Malek-Kandi show good tolerance to disease in a few researches carried out in Iran. Results of field and greenhouse experiments are relative similar and show good correlation. It seems that using these ecotypes in different regions of Iran especially cold regions in which disease is frequently observed and considering other management methods such as appropriate cutting can be considerably decrease the occurrence of the disease and the crop loss.
Type of Study:
Extentional |
Subject:
Special Received: 2013/12/7 | Accepted: 2014/03/18