Study On The Methods Of Screening And Identification Of Rice Germplasm For Resistance To The Rice Leafroller Cnaphalocrocis Medinalis (Güenée) And On Resistant Mechanism

We selected seventeen rice varieties and identified their resistant standards to the rice leaf folder, Cnaphalocrocis medinalis Guenée. The present study investigated the relationship between resistance of rice to C. medinalis and physical and chemical characteristics of rice and effect on development of C. medinalis. In addition, selectivity and feeding and disperse behaviour of C. medinalis larvae to different rice varieties were also examined using leaf in vitro. The objective of the present study was to examine resistant mechanism of rice to the insect and improve identification methods of resistance.1. Damage scale was grouped in to 4 rates, i.e., 3. 5, 7 and 9 rate from the method of IRRI, respectively. Damage scales of 17 rice varieties tested were attributed to 4 rates. The results showed that there were significant correlations between leaf width and chlorophyll content and resistance, in contrast, no correlations between leaf length and plant height and resistance. Resistance elevated with increase of Mg content in rice leaf. Moreover, there was a significant difference on Mg contents in leaf among 4 rates.2. There was a significant positive correlation between the number of egg-laid by adult female and damage rate. There were no significant correlations between developmental duration of the larvae, length of 5th instar larvae, pupae weight and emergence rate of adult moth and damage rate.3. Test experiment of leaf in vitro showed that there were significant correlations between selectivity of 3rd instar feeding, dispense behaviour of 1st instar and amount of 3rd instar feeding and rice resistance.4. The present findings proved that leaf test in vitro was a good identification method of resistance of rice to C. medinalis.