Genotype specific host resistance for Phytophthora in black pepper (Piper nigrum L.)

Abstract

Phytophthora foot rot is a devastating disease in black pepper which is caused byP. capsici. Using host resistance is a major component in the integrated pest management of this disease. To explore the hostresistance pattern, we studied the genotype specific differential expression of important pathogenesis related geneb1, 3 glucanase and 5 R gene loci from resistant and susceptible varieties of black pepper.The relative expression ofb1, 3 glucanase was up regulated in resistant variety and down regulated insusceptible variety. R gene loci Pn CNBS 5, CNBS 3 and Pn CNBS 2 showed up regulation in susceptible variety in the early hours of infection while resistant genotype recorded its down regulation till 72 suggesting that the selective down expression of these loci may be attributed to the resistance in the resistant variety. These R genes may be the susceptibility genes (S-genes) in black pepper for Phytophthora. The high relative expression of the R gene locus Pn CNBS 4 and Pn CNBS 1 in resistant genotype at early hours shows their involvement in resistance towards P. capsici.The differential expression of the R gene loci shows the genotype specific functional significance for Phytophthora resistance.