Brown planthopper (BPH), Nilaparvata lugens Stal is one of the most serious rice pests in Sri Lanka.The study evaluated the nature of BPH resistance in seventeen O. nivara (

The study was carried out as pot experiments using a Green Chilli variety, MI 2, and a Curry Chilli variety, Hungarian Yellow Wax (HYW) at the research field, Faculty of Agriculture, University of Ruhuna. The basal soil mixture was prepared using coir dust, sand, soil and cow-dong (1:1:1 control). Four different potting mixtures were prepared by adding tea waste, compost and inorganic fertilizer. The experiment was carried out according to complete randomized block design with four replicates at the rate of 8 plants per replicate. Plant height (cm), number of pods/plant, weight of pods per plant (g), pod length (cm) and pod appearance were recorded. Carbon-dioxide (CO 2 ) evolution method was applied to observe soil microbial activity in different soil mixtures.

Gene bph2 is one of the 21 brown planthopper (BPH), Nilaparvata lugens (Stal) resistant genes identified so far in several indica cultivars and wild relatives. The present study evaluated Oryza nivara accessions collected from different locations in Sri Lanka for bph2 and, antibiosis and antixenosis effects of O. nivara accessions harbouring bph2 gene on BPH. The five O. nivara accessions; WRAC 02, WRAC 04, WRAC 07, WRAC 21 and WRAC 25 amplified the resistant band (300 bp) indicating the presence of the bph2 gene in their genomes. The level of resistance observed in these accessions was high and showed negative effects on honeydew production and nymphal survival (antibiosis) and revealed antixenosis action against nymphs and oviposition. In addition, dynamic response mechanisms of BPH against O. nivara accessions that possess bph2 was found, which may be indicative of the complex structure of genetics of resistance of these accessions. Substantial level of resistance similar to that in Ptb 33, observed in O. nivara accessions WRAC 02, WRAC 04 gives a clue to the possible existence of polygenic resistance as detected in Ptb 33. Results of this study highlighted the possibility of the use of O. nivara accessions that possess bph2 gene in their genome as a potential source of resistance in pyramiding of genes for BPH resistance to avoid the genetic uniformity of BPH resistant rice varieties cultivated in Sri Lanka in the future.

This study evaluates the basis of brown planthopper (BPH) resistance in Oryza nivara (9864, WRAC 04), Oryza eichingeri (TC 01, TC 02), IR 54751-2-34-10-6-2 (an introgression line of Oryza officinalis), Ptb 33, Bg 380 and Bg 379/2 accessions by screening for resistance, and characterizes the genes by molecular techniques. Four BPH populations reared on Ptb33, Bg 380, Bg 379/2, IR 54751-2-34-10-6-2 and a virulent BPH population collected from rice fields in Kegalle area Sri Lanka were used for screening tests. Screening for resistance was conducted following the standard honeydew test and molecular screening was carried out using specific molecular markers for bph2, Bph10 and Bph13 genes. Results of the screening tests for resistance showed that the level of resistance of the tested wild rice accessions (O. nivara and O. eichingeri) was not significantly different from that of Ptb 33. These accessions also showed high level of resistance to all the BPH populations used in this study. Molecular screening revealed positive results with O. nivara (WRAC 04) accession for bph 2 and Bph 13 markers and O. eichingeri derived lines (TC 01 & TC 02) for Bph 13 marker. Results showed that the emergence of virulent biotype in field rice cultivations have the potential to overcome the BPH resistance in Bg 379/2.