A cDNA microarray approach to decipher lentil (Lens culinaris) responses to Ascochyta lentis

Ascochyta blight, caused by Ascochyta lentis Vassilievsky, is an important fungal disease of lentil (Lens culinaris subsp. culinaris). Manifestation of disease in plants is due to differential expression of genes in the both host and the pathogen. Identification of genes that are differentially expressed in varieties with resistance to A. lentis will lead to the accurate selection and development of crop varieties with increased resistance. To elucidate the complex network of genes underlying A. lentis resistance in lentil, a targeted genomics approach was utilised. The present study reports for the first time the use of microarray technology to study gene expression in lentil, specifically in response to A. lentis inoculation in a highly resistant (ILL7537) and highly susceptible (ILL6002) lentil variety. Ninety genes were differentially expressed in ILL7537 and 95 genes were differentially expressed in ILL6002. The expression profiles of the two varieties showed substantial difference in type and time of genes that were expressed in response to A. lentis. The resistant variety showed early upregulation of PR4 and 10 proteins and other defence-related genes. The susceptible genotype showed early downregulation of defence-related genes. Real-time RT¿PCR was used to verify microarray expression ratios. The resistant and susceptible lentil varieties differ not only in the type of genes expressed but also in the time and level of expression in response to A. lentis inoculation. Different components of the defence mechanism and key putative defence genes were identified by comparing the transcriptional profiles of the susceptible and resistant lentil genotypes. Following further functional characterisation, these candidate ascochyta blight resistance genes may be used in future strategic A. lentis resistance breeding programs.