2017 ASHS Annual Conference

Gerbera daisy is one of the most popular flowers in the world and an important floricultural crop in a number of countries. Powdery mildew (PM) can rapidly infect gerbera leaves and flowers and is considered as the most common and destructive disease in commercial production and landscape use. In recent years, improving PM resistance has become a priority breeding objective in gerbera breeding. Previously we identified two gerbera breeding lines highly resistant to the PM caused by Podosphaera xanthii (Podosphaera fusca). The PM resistance in one of the breeding lines, UFGE 31-19, has been transferred into several new garden-type gerbera cultivars. Previous genetic mapping and quantitative trait locus (QTL) analysis identified two linked QTL (Rpx1 and Rpx2) in UFGE 31-19. To identify genes associated with these loci, total RNA was isolated from leaves of a PM-resistant progeny (UFGE 4033) of UFGE 31-19 and a PM-susceptible gerbera line and converted into cDNA, which was then sequenced on an Illumina HiSeq^TM 2000 (transcriptome sequencing). Assembly of the transcriptomes resulted in 430,251 genes and 528,630 transcripts. The assembled transcriptomes contain approximately 292 Mb with an average GC content of 43.6%. The N50 of the assembly based on all transcripts was 708 bases. More than 77% of the total reads were mapped to the assembled transcriptome and more than 66% paired-end reads aligned concordantly to the assembly. Some genes expressed in the leaves of UFGE 4033 were highly similar to disease resistance genes that have been cloned in other plants.