NBS-LRR Gene Expression of Buffalograss Challenged With Leaf Spot Pathogen.

Buffalograss (Buchloe dactyloides [Nutt.] Engelm.) is a native turfgrass having exceptional drought, heat and cold tolerance. Leaf spot caused by Curvularia inaequalis is an important disease of buffalograss reducing visual quality. Breeding disease-resistant varieties plays a vital role in future success of promoting buffalograss as a low-maintenance turfgrass. Conventional resistance breeding based on inoculation, rating and selection is difficult and time consuming. In the present study the expression of seven resistance gene-like (RGL) sequences of buffalograss were evaluated. These RGL sequences have conserved domains for coding NBS-LRR proteins important for pathogen recognition. Two leaf spot susceptible (Prestige and 7-3453-50) and two resistant (95-55 and 7-3459-17) buffalograss lines were inoculated with a spore suspension of C. inaequalis. The control pots were sprayed with water. All pots were covered with clear plastic bags and kept in a greenhouse at 28° C. After 10 d, when susceptible lines showed distinct disease symptoms, leaf samples were harvested and total RNA extracted from all plants. Quantitative real-time PCR assays were performed to detect the expression of RGLs on individual lines. Four RGL sequences (RGL1, 2, 5 and 6) showed expression with RGL 1 and RGL 2 having higher expression in inoculated resistant lines compared to the unchallenged resistant lines. Inoculated susceptible lines did not show differential expression for any of the RGL sequences. Expressions of all genes in inoculated 95-55 were significantly higher than in inoculated Prestige. Similarly, 7-7359-17 had higher expression of all four RGLs than 7-3453-50. RGL 1 had higher basal level of expression in healthy 95-55 than in Prestige. Basal expression levels of RGL 2 and RGL 6 in resistant line 7-7359-17 were significantly higher than susceptible line 7-3453-50. These results show the potential of using RGL 1, 2, and 6 in conjunction as molecular markers for screening buffalograss lines resistant to leaf spot.