Antixenosis and antibiosis effects of Oryza nivara accessions harbouring bph2 gene on brown planthopper [Nilaparvata lugens (Stal)]

Abstract

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.