1a.Objectives (from AD-416)
To map and develop molecular markers linked to the fusarium wilt resistance (race. 1)gene in watermelon.
1b.Approach (from AD-416)
The cooperator has developed parental lines and BC1 and F2 populations segregating for FW (race. 1)resistance. Previous experiments conducted by the cooperator with these populations showed that the FW (race. 1)resistance is controlled by a single dominant gene. The cooperator grew 200 F2 plants and collected leaf samples for DNA analysis from each of these F2 plants. The cooperator is self-pollinating each of the F2 plants in order to produce F3 families. These F3 families will be used by the cooperator for progeny evaluation and identifying the FW (race. 1)resistant and susceptible F2 plants. The cooperator will provide ARS the F3 progeny evaluation data and leaf samples of the F2 plants (and their resistant and susceptible parental lines). The ARS scientists will isolate DNA from each of the parental lines and F2 leaf samples, and conduct genetic mapping analysis to identify markers linked to the FW-resistance gene.
This research relates to inhouse objective 1: Determine the genetic control of resistance to important diseases and pests of watermelon and release resistant breeding lines developed.
The F3 families used in this study were reevaluated for resistance to fusarium wilt (FW). Based on results of the F3 screens for resistance, we have generated new bulks of deoxyribonucleic acid (DNA) from resistant F2 plant tissues as well as susceptible bulks. We are now re-screening these DNA bulks using polymerase chain reaction (PCR) primers. Several unique DNA fragments have been identified and are being examined to see if they are linked to resistance. We have also generated a new watermelon population from the resistant cultivar Calhoun grey and the ultra susceptible cultivar Sugar baby. One hundred and ten F2-derived lines have been established. We have generated F3 and F4 lines of resistant plants that are being re-screened for FW resistance.
Progress was monitored by ARS scientists and cooperators frequently via telephone calls and emails, attendance at the Cucurbitacea 2010 conference, and at the Watermelon Research and Development Working Group Annual Meeting that took place in February of 2010 in Orlando, Fl.