Evaluation of partial resistance to Magnaporthe grisea Sacc. in rice cultivars at the seedling stage under upland nursery and greenhouse conditions

In this research work the relative resistance of rice (Oriza sativa L.) cultivars to the Blast disease, resulted by the fungi Magnaporthe grisea Sacc. was determined using their progressive disease curve. Fifty eight internal cultivars and the line of Omidbahksh were tested under greenhouse and field conditions. Phenotyping tests were conducted on blast nursery uisng a randomized complete block design with two replicates. In the greenhouse test two species of blast IA-82 and IA-90 were tested in a randomized block design with two replicates. The tested traits consisted of infection type (IT), percent of diseased leaf area (DLA) (in nursery) and lesion number (LN) and size (LS,mm2) in greenhouse condition. Under upland nursery conditions, IR24, F125 and F120-2 exhibited the lowest disease severity (IT=1-2) and area under the growth progressive curve (AUDPC= 20-30). Varieties and lines like Domsiah, Hasani, F35-1 and F63-3 showed the highest disease severity (IT=3-5) and area under the growth progressive curve (AUDPC=50-60). The different rice cultivars indicated different responses versus the two fungal species. Overall, all genotypes were divided in three groups with high, intermediate and susceptible resistance to the disease. To achieve durable resistance, cultivars with partial resistance are preferred.