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United States Department of Agriculture

Agricultural Research Service

Research Project: RESEARCH, ACQUISITION, MANAGEMENT, AND DOCUMENTATION OF PLANT GENETIC RESOURCES Title: Cloning and characterization of resistance gene candidate sequences and molecular marker development in gerbera (Gerbera hybrida)

Authors
item Song, Xiaohe -
item Deng, Zhanao -
item Gong, Li -
item Hu, Jinguo
item Ma, Qing -

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 2012
Publication Date: August 17, 2012
Citation: Song, X., Deng, Z., Gong, L., Hu, J., Ma, Q. 2012. Cloning and characterization of resistance gene candidate sequences and molecular marker development in gerbera (Gerbera hybrida). Scientia Horticulturae 145:68–75.

Interpretive Summary: Gerbera (Gerbera hybrida) is an important floricultural crop in the United States and worldwide. Powdery mildew (PM) is the most common and destructive disease in gerbera production and landscape use. Improving powdery mildew resistance has become an important breeding objective in gerbera. This paper report the development of genomic resources and DNA markers for disease resistance breeding in gerbera. Eighty-four gerbera RGC sequences (GhRGCs) were identified from cloned PCR products amplified from powdery mildew (PM)-resistant gerberas with degenerate oligonucleotide primers from two conserved motifs of plant disease resistance genes (R-genes). Nineteen GhRGC sequences could be translated into polypeptides with =90% amino acid identity.Bulked segregant analysis was performed using the target region amplification polymorphism (TRAP) marker system to develop molecular markers for the major genes. Thirty GhRGC-derived primers detected 242 DNA bands that were polymorphic between UFGE 4033 (highly resistant to PM) and ‘Sunburst Snow White’ (highly susceptible to PM). One sequence characterized amplified polymorphism (SCAR) and 11 cleaved amplified polymorphic site (CAPS) markers developed were polymorphic between the UFGE4033 and 'Sunburst Snow White' and could be useful in marker-assisted selection to expedite gerbera breeding. This study represents the first effort to sample and characterize R-gene candidate sequences in gerbera.

Technical Abstract: Improving disease resistance has become an important breeding objective in gerbera, one of the most important floricultural crops in the world. Development and application of molecular markers are expected to assist selection of gerberas with improved disease resistance. The availability of resistance gene candidate (RGC) sequences has accelerated the development of molecular markers for disease resistance traits in numerous plants. In this study, 84 gerbera RGC sequences (GhRGCs) were identified from cloned PCR products amplified from powdery mildew (PM)-resistant gerberas with degenerate oligonucleotide primers from two conserved motifs of plant disease resistance genes (R-genes). Nineteen GhRGC sequences could be translated into polypeptides with =90% amino acid identity. Multiple sequence alignment analysis of the 19 representative polypeptide sequences suggests two major clusters of gerbera RGCs. Twelve GhRGCs in cluster 1 contain the typical motifs of the toll and interleukin receptor–nucleotide binding site–leucine-rich repeat (TIR–NB–LRR) class R-genes within the nucleotidebinding site (NB) domain, and the seven GhRGCs in cluster 2 possess the typical motifs of the coiled coil–nucleotide binding site–leucine-rich repeat (CC–NB–LRR) class R-genes in the NB domain. The 19 GhRGCs were further divided into nine sub-families that share 15–50% amino acid identity. Thirty specific oligonucleotide primers were designed from 15 GhRGCs and tested on gerbera breeding line UFGE 4033 and ‘Sunburst Snow White’ that are PM-resistant and PM-susceptible, respectively, and are parents of two mapping populations for developing molecular markers for PM resistance. One sequence characterized amplified polymorphism (SCAR) and 11 cleaved amplified polymorphic site (CAPS) markers were developed and were polymorphic between the two parents. When used with the target region amplification polymorphism (TRAP) marker system, the 30 GhRGC-derived primers detected 242 additional DNA bands that were polymorphic between UFGE 4033 and ‘Sunburst Snow White’. This study represents the first effort to sample and characterize R-gene candidate sequences in gerbera. The obtained sequences may provide a valuable entry point to obtain full-length or additional sequences of gerbera NB–LRR genes. The SCAR, CAPS and TRAP markers developed may be valuable for mapping of genes or quantitative trait loci responsible for disease resistance in gerbera.

Last Modified: 10/21/2014