Identification of NBS-LRR Resistance Gene Analogues (RGA) from Rose (IIHRR13-4) Resistant to Powdery Mildew (Podosphaera pannosa (Wallr.:Fr.) de Bary)

Abstract

Resistance is the best strategy to manage powdery mildew (Podosphaera pannosa (Wallr.:Fr.) de Bary) of rose. Identification of resistant genes (R genes) from plant species will help in breeding programs. Nucleotide Binding Site - Leucine Rich Repeats (NBS- LRR) is a major class of R gene family in plants. This study reports the identification and molecular characterization of resistance gene analogues from roses maintained at ICAR- Indian Institute of Horticultural Research (IIHR). The powdery mildew resistant line IIHRR13-4 was compared with the susceptible commercial cultivar, konfetti. PCR based approaches with degenerative primers based on different conserved motifs of NBS-LRR were employed to isolate resistance gene analogues (RGAs) from rose. Eleven RGAs (IIHRR13-4R1, IIHRR13-4R2, IIHRR13-4R3, IIHRR13-4R4, IIHRR13-4R5, IIHRR13- 4R6, IIHRR13-4R7, IIHRR13-4R8 IIHRR13-4R9 and IIHRR13-4R10) were identified from powdery mildew resistant germplasm line, IIHRR13-4, based on the sequence and similarity to RGAs from rosaceae family and other crops. The major similarity to rose RGAs reported are from Fragaria vesca, Rosa hybrid cultivar, Prunus and Rosa chinensis. RGAs isolated from IIHRR13-4 belonged to Toll Interleukin Receptor (TIR)-NBS-LRR and Non-TIR-NBS-LRR RGAs (Lecine Zipper (LZ) type). Different motifs of RGAs identified were P-loop, RNBS A, kinase 2, kinase 3a, RNBS-D and GLPL of NBS domain. This study reports the existence of resistance at genetic level in powdery mildew resistant genotype IIHRR13-4. These RGAs will be useful for mapping and characterization of R genes in IIHRR13-4 and breeding for improved powdery mildew resistance in roses.