Transcriptomic Analysis of Crape Myrtle (Lagerstrosmia indica) to Identify Genes Associated with Powdery Mildew Resistance

The genus Lagerstroemia (common name crape myrtle) is a deciduous shrub or small tree, originaly native to southeast Asia and has became one of the most distinctive and popular summer flowering woody ornamentals anywhere south of USDA from east to west coast. Powdery mildew was one of the most serious disease problems of crape myrtle in the U.S. Disease resistant breeding in crape myrtle has been achieved significant achievements since another species L. fauriei being introduced into breeding program. However, development of genetic resources for genomic-based breeding in this species has lagged behind other crops. Recent advances in next generation sequencing technologies have enabled the development of genetic resources for plants. In this study, we used RNA-seq technology to investigate and compare transcriptomes in powdery mildew resistant (Carolina Beauty) and susceptible (Natchez) L. indica cultivars to generate the leave-responsive gene expression profiles and identify candidate genes related to disease resistance for further study. The comparison of the transcriptomes between the two genotypes showed that there were 475 highly expressed genes. Although we do not know if these genes are related to the disease resistance, we examined the expression of 21 potential differentiated genes through RT-PCR. Of them, 16 had different expressions with 7 genes had larger than 2 fold difference between these two genotyps. The data set generated in this study provides preliminary evidence for some candidate genes that are related to disease resistance in genus Lagerstroemia, and will help discover new genes for expediting crape myrtle disease breeding.