Mapping and candidate-gene screening of the novel Turnip mosaic virus resistance gene retr02 in Chinese cabbage ( Brassi
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ORIGINAL PAPER
Mapping and candidate-gene screening of the novel Turnip mosaic virus resistance gene retr02 in Chinese cabbage (Brassica rapa L.) Wei Qian • Shujiang Zhang • Shifan Zhang • Fei Li • Hui Zhang • Jian Wu • Xiaowu Wang John A. Walsh • Rifei Sun
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Received: 7 September 2011 / Accepted: 16 August 2012 / Published online: 21 September 2012 Ó Springer-Verlag 2012
Abstract The extreme resistance to Turnip mosaic virus observed in the Chinese cabbage (Brassica rapa) line, BP8407, is monogenic and recessive. Bulked segregant analysis was carried out to identify simple sequence repeat and Indel markers linked to this recessive resistance gene, termed recessive Turnip mosaic virus resistance 02 (retr02). Mapping of PCR-specific Indel markers on 239 individuals of a BP8407 9 Ji Zao Chun F2 population, located this resistance gene to a 0.9-cM interval between two Indel markers (BrID10694 and BrID101309) and in scaffold000060 or scaffold000104 on chromosome A04 of the B. rapa genome. Eleven eukaryotic initiation factor 4E (eIF4E) and 14 eukaryotic initiation factor 4G (eIF4G) genes are predicted in the B. rapa genome. A candidate gene, Bra035393 on scaffold000104, was predicted within the mapped resistance locus. The gene encodes the eIF (iso)4E protein. Bra035393 was sequenced in BP8407 and Ji Zao Chun. A polymorphism (A/G) was found in exon 3 between BP8407 and Ji Zao Chun. This gene was analysed in four resistant and three susceptible lines. A correlation was observed between the amino acid substitution
Communicated by F. Ordon. W. Qian S. Zhang S. Zhang F. Li H. Zhang J. Wu X. Wang R. Sun (&) Department of Chinese Cabbage, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China e-mail: [email protected] W. Qian e-mail: [email protected] J. A. Walsh School of Life Sciences, University of Warwick, Wellesbourne, Warwick CV35 9EF, UK
(Gly/Asp) in the eIF(iso)4E protein and resistance/susceptibility. eIF(iso)4E has been shown previously to interact with the TuMV genome-linked protein, VPg.
Introduction Chinese cabbage (Brassica rapa L.) originates in China and is one of its most important vegetable crops in the world, with the largest planting area and yield (Cao et al. 2006); however, outbreaks of Turnip mosaic virus (TuMV) greatly decrease yield and quality. TuMV is a member of the Potyvirus genus (family Potyviridae) and is the only potyvirus known to infect brassicas (Tomlinson 1987; Walsh and Jenner 2002). It has the widest host range of any member of the Potyvirus genus (Shukla et al. 1994), infecting a wide range of cultivated plant species (Edwardson and Christie 1991) and causing significant economic loss in brassica crops (Shattuck 1992). TuMV was first described in B. rapa by Gardner and Kendrick (1921) and Schultz (1921) and has since been widely studied. It is difficult to control because of its wide host range and non-persistent stylet-borne mode of transmission by aphids (Walsh and Jenner 2002). Chemical control of the disease is inef
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