AUTHOR=Choi Seula , Lee Joung-Ho , Kang Won-Hee , Kim Joonyup , Huy Hoang N. , Park Sung-Woo , Son Eun-Ho , Kwon Jin-Kyung , Kang Byoung-Cheorl 

TITLE=Identification of Cucumber mosaic resistance 2 (cmr2) That Confers Resistance to a New Cucumber mosaic virus Isolate P1 (CMV-P1) in Pepper (Capsicum spp.)

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01106

DOI=10.3389/fpls.2018.01106

ISSN=1664-462X

ABSTRACT=<p><italic>Cucumber mosaic virus</italic> (CMV) is one of the most devastating phytopathogens of <italic>Capsicum</italic>. The single dominant resistance gene, <italic>Cucumber mosaic resistant 1</italic> (<italic>Cmr1</italic>), that confers resistance to the CMV isolate P0 has been overcome by a new isolate (CMV-P1) after being deployed in pepper (<italic>Capsicum annuum</italic>) breeding for over 20 years. A recently identified Indian <italic>C. annuum</italic> cultivar, “Lam32,” displays resistance to CMV-P1. In this study, we show that the resistance in “Lam32” is controlled by a single recessive gene, <italic>CMV resistance gene 2</italic> (<italic>cmr2</italic>). We found that <italic>cmr2</italic> conferred resistance to CMV strains including CMV-Korean, CMV-Fny, and CMV-P1, indicating that <italic>cmr2</italic> provides a broad-spectrum type of resistance. We utilized two molecular mapping approaches to determine the chromosomal location of <italic>cmr2</italic>. Bulked segregant analysis (BSA) using amplified fragment-length polymorphism (AFLP) (BSA-AFLP) revealed one marker, cmvAFLP, located 16 cM from <italic>cmr2</italic>. BSA using the Affymetrix pepper array (BSA-Affy) identified a single-nucleotide polymorphism (SNP) marker (Affy4) located 2.3 cM from <italic>cmr2</italic> on chromosome 8. We further screened a pepper germplasm collection of 4,197 accessions for additional CMV-P1 resistance sources and found that some accessions contained equivalent levels of resistance to that of “Lam32.” Inheritance and allelism tests demonstrated that all the resistance sources examined contained <italic>cmr2</italic>. Our result thus provide genetic and molecular evidence that <italic>cmr2</italic> is a single recessive gene that confers to pepper an unprecedented resistance to the dangerous new isolate CMV-P1 that had overcome <italic>Cmr1</italic>.</p>