Morpho-molecular screening of zinc rich rice landraces for Biotype 4 brown planthopper resistance

Field screening was undertaken with 100 zinc rich rice landraces and four checks following Standard Seedbox Screening Technique (SSST) to confirm their resistance and susceptible reactions for Brown planthopper Biotype 4 under lab conditions. The highly resistant reaction (1) was noticed in the resistant check (PTB 33) while, highly susceptibility was recorded in susceptible checks, TN1 and MTU 7029. The genotypes, GM-3 and GM-86 also showed resistant reaction (1.0) under both the findings of field and Standard Seedbox Screening Technique (SSST). Based on the phenotypical damage scores (1-3), 26 zinc rich rice landraces and the four checks (PTB 33, BM 71TN1 and MTU 7029) were identified for molecular characterization using 37 SSR markers (28 gene linked and 11 gene specific markers). Out of the 28 gene linked markers, 26 markers were confirmed to be polymorphic. A total number of 62 alleles were obtained through 26 polymorphic markers with an average of 2.32 alleles per locus. The polymorphic information content (PIC) value ranged from 0.083 (RM8212) to 0.705 (RM19291) with an average of 0.50. The markers, namely, RM19291 (Bph3, Bph4 and Bph32), RM588 and RM190 linked to the resistant genes (Bph3 and Bph4) and located on Chromosome 6 showed resistance to biotype 4. Among the markers, RM19291 recorded highest PIC value (0.705). The genotypes were grouped into three clusters based on the molecular screening data. GM-3 and GM-86 were paired in Cluster I together with the resistant checks, PTB 33 and BM7 in conformity with the phenotypic data of field and Standard Seedbox Screening Technique for BPH. Information on genetic resistance and diversity of the lines would be useful in gene mapping and marker assisted breeding for the development of zinc rich BPH tolerant lines in rice.