Non-synonymous single nucleotide polymorphisms in the watermelon eIF4E gene are closely associated with resistance to zucchini yellow mosaic virus.
Zucchini yellow mosaic virus (ZYMV) is one of the most economically important potyviruses infecting cucurbit crops worldwide. Using a candidate gene approach, we cloned and sequenced eIF4E and eIF(iso)4E gene segments in watermelon. Analysis of the nucleotide sequences between the ZYMV-resistant watermelon plant introduction PI 595203 (Citrullus lanatus var. lanatus) and the ZYMV-susceptible watermelon cultivar 'New Hampshire Midget' ('NHM') showed the presence of single nucleotide polymorphisms (SNPs). Initial analysis of the identified SNPs in association studies indicated that SNPs in the eIF4E, but not eIF(iso)4E, were closely associated to the phenotype of ZYMV-resistance in 70 F(2) and 114 BC(1R) progenies. Subsequently, we focused our efforts in obtaining the entire genomic sequence of watermelon eIF4E. Three SNPs were identified between PI 595203 and NHM. One of the SNPs (A241C) was in exon 1 and the other two SNPs (C309A and T554G) were in the first intron of the gene. SNP241 which resulted in an amino acid substitution (proline to threonine) was shown to be located in the critical cap recognition and binding area, similar to that of several plant species resistance to potyviruses. Analysis of a cleaved amplified polymorphism sequence (CAPS) marker derived from this SNP in F(2) and BC(1R) populations demonstrated a cosegregation between the CAPS-2 marker and their ZYMV resistance or susceptibility phenotype. When we investigated whether such SNP mutation in the eIF4E was also conserved in several other PIs of C. lanatus var. citroides, we identified a different SNP (A171G) resulting in another amino acid substitution (D71G) from four ZYMV-resistant C. lanatus var. citroides (PI 244018, PI 482261, PI 482299, and PI 482322). Additional CAPS markers were also identified. Availability of all these CAPS markers will enable marker-aided breeding of watermelon for ZYMV resistance.
Ling
Kai-Shu
KS
U.S. Vegetable Laboratory, U.S. Department of Agriculture, Agriculture Research Service, Charleston, SC 29414, USA. kai.ling@ars.usda.gov
Harris
Karen R
KR
Meyer
Jenelle D F
JD
Levi
Amnon
A
Guner
Nihat
N
Wehner
Todd C
TC
Bendahmane
Abdelhafid
A
Havey
Michael J
MJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D029773:Citrullus / Q000235:genetics / Q000821:virology; D018556:Crops, Agricultural / Q000235:genetics / Q000821:virology; D003433:Crosses, Genetic; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry / Q000235:genetics*; D008040:Genetic Linkage; D005819:Genetic Markers; D007113:Immunity, Innate / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000821:virology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D017800:Potyvirus / Q000472:pathogenicity*; D020033:Protein Isoforms / Q000235:genetics; D017434:Protein Structure, Tertiary
D039561:Eukaryotic Initiation Factor-4E; D005819:Genetic Markers; D010940:Plant Proteins; D020033:Protein Isoforms