Resistance to geminiviruses in watermelons

Abstract

The present invention is directed to watermelon plant and seed, namely of C. lanatus, which are resistant to geminiviruses, especially to begomoviruses including WmCSV, comprising in their genome introgressed sequences from C. colocynthis conferring resistance to said viruses, when present homozygously. The introgressed sequences are preferably characterized by defined alleles of SNPs on chromosome 6. The introgressed sequences can be chosen from those present in the genome of a plant of Citrullus lanatus—WMCSVR accession number NCIMB 42197. The invention is also directed to parts of these resistant plants, as well as progeny, to the use of these plants for introgressing the resistance in another genetic background, as well as to different methods for obtaining resistant watermelon plants or seeds.

1 . A  Citrullus lanatus  seed having in its genome introgressed sequences from  Citrullus colocynthis  conferring resistance to geminiviruses only when present homozygously, wherein said introgressed sequences are located on homologous chromosome 6, within the chromosomal region delimited by telomere and SNP#10 (SEQ ID No:10) and comprising SNP#1 (SEQ ID N:1). 
     
     
         2 . The  C. lanatus  seed according to  claim 1 , wherein said introgressed sequences conferring the resistance, are chosen from the introgressed sequences from  C. colocynthis  present in the genome of a seed  Citrullus lanatus —WMCSVR, deposited at NCIMB accession number NCIMB-42197, on chromosome 6. 
     
     
         3 . Seed according to  claim 1 , wherein said introgressed sequences are located at one or more of the following loci:
 locus encompassing SNP#3 (SEQ ID No:3); and/or   locus encompassing SNP#9 (SEQ ID No:9).   
     
     
         4 . Seed according to  claim 1 , wherein said introgressed sequences are in linkage disequilibrium with allele C of SNP#3 (SEQ ID No:3) and/or with allele C of SNP#9 (SEQ ID No:9), preferably with a positive linkage disequilibrium. 
     
     
         5 . Seed according to  claim 1 , wherein said introgressed sequences are located in its genome at less than 20 cM, preferably less than 15 cM, preferably less than 10 cM, preferably less than 5 cM of the locus corresponding to SNP#3 (SEQ ID No:3). 
     
     
         6 . Seed according to  claim 1 , wherein said introgressed sequences are located in its genome at less than 20 cM, preferably less than 15 cM, preferably less than 10 cM, preferably less than 5 cM of the locus corresponding to SNP#9 (SEQ ID No:9). 
     
     
         7 . Seed according to  claim 1 , wherein the presence of said introgressed sequences on each allele of chromosome 6 is characterized by:
 the presence of allele C of SNP#3 (SEQ ID No:3), and the absence of allele T for said SNP; and/or   the presence of allele C of SNP#9 (SEQ ID No:9), and the absence of allele T for said SNP.   
     
     
         8 . The  C. lanatus  seed according to  claim 1 , wherein said introgressed sequences are located within the chromosomal interval defined by SNP#1 (SEQ ID No:1) and SNP#10 (SEQ ID No:10) on chromosome 6. 
     
     
         9 . Seed according to  claim 1 , wherein said resistance is a resistance to begomoviruses. 
     
     
         10 . Seed according to  claim 9 , wherein the begomovirus is Watermelon Chlorotic Stunt Virus (WmCSV) or Squash Leaf Curl Virus (SCLV). 
     
     
         11 . Seed according to  claim 1 , wherein said seed is diploid, triploid, tetraploid and/or allopolyploid. 
     
     
         12 . A  C. lanatus  plant resistant to geminiviruses grown from a seed according to  claim 1 . 
     
     
         13 . Hybrid plant of  C. lanatus , obtainable by crossing a plant resistant to geminiviruses according to  claim 12  with a susceptible plant of  C. lanatus.    
     
     
         14 . A plant, explants, scion, cutting, seed, fruit, rootstock, pollen, ovules, and/or plant parts of  C. lanatus  having in its genome introgressed sequences from  C. colocynthis  conferring resistance to geminiviruses only when present homozygously,
 wherein said plant, explants, scion, cutting, seed, fruit, rootstock, pollen, ovules, and/or plant parts is obtainable from a seed according to  claim 1 .   
     
     
         15 . A cell of a  C. lanatus  plant according to  claim 12 , comprising in its genome introgressed sequences from  C. colocynthis  on chromosome 6 conferring resistance to geminiviruses only when present homozygously. 
     
     
         16 . A tissue culture of regenerable cells of the plant according to  claim 12 , wherein the regenerable cells are derived from embryos, protoplasts, meristematic cells, callus, pollen, leaves, anthers, stems, petioles, roots, root tips, fruits, seeds, flowers, cotyledons, and/or hypocotyls, and contain in their genome introgressed sequences from  C. colocynthis  on chromosome 6 conferring resistance to geminiviruses only when present homozygously. 
     
     
         17 - 18 . (canceled) 
     
     
         19 . A method for the production of  C. lanatus  plants resistant to geminiviruses, comprising the steps of:
 a) Crossing a plant grown from the deposited seeds NCIMB 42197 and a susceptible or less resistant  C. lanatus  plant,   b) Selecting a plant in the progeny thus obtained bearing sequences conferring resistance to geminiviruses only when present homozygously;   c) Self-pollinating one or several times the plant obtained at step b) and selecting a resistant plant in the progeny thus obtained;   
       wherein SNPs markers are used in steps b) and c) for selecting plants bearing sequences conferring resistance to geminiviruses only when present homozygously and/or plants resistant to geminiviruses. 
     
     
         20 . (canceled) 
     
     
         21 . A method for breeding  C. lanatus  plants resistant to geminiviruses, comprising the steps of crossing a plant grown from the deposited seeds NCIMB 42197, with a  C. lanatus  plant. 
     
     
         22 - 23 . (canceled)