On Monday and Tuesday, I helped Konstantin, a graduate student in Bruce’s lab, perform a detached leaf assay for Downy Mildew, another fungal disease of grapes. Konstantin’s experiment is very similar to mine, in that he is attempting to find QTLs in a mapping population for resistance to disease. However, in my project, we rate for disease susceptibility/resistance in the vineyard, whereas he is rating and inoculating in the lab, where the environment can be more controlled.
The first day, we collected leaves from every individual in the population. The population we used was the progeny of a cross of ‘Horizon’ x V. cinerea; ‘Horizon’ is a sibling of ‘Cayuga White’, a popular Cornell-produced hybrid winegrape, while Vitis cinerea is a wild american grape variety, with some disease resistance. The second day, we set up the experiment: first we surface sterilized the leaves with a bleach solution, then we cut out 1cm leaf disks and placed them on agar. The next day, Konstantin inoculated each leaf with 50uL of a solution of spores, and returned every day afterward to rate each individual for resistance based on the prevelance of sporangiaphores (the sporeulating organ of the fungi).
On Tuesday afternoon, I headed home from work a bit early to make dinner and change into more mosquito-resistant clothes, and arrived back to work at 6pm for evening Black Rot inoculations with Bruce and Beth. It took us about 3 hours to finish inoculating the ‘Horizon’ x V. rupestris population, and the sun was starting to set by the time we finished.
The previous day, we had come out to flag the shoots we were going to inoculate–3 per vine, with 150 vines total–with strips of tape, and Beth sprayed the basal cluster on each shoot with an aerosol-ized solution of spores. Bruce and I followed behind her, tying plastic bags over the sprayed clusters to maintain humidity overnight, as a humid environment favors infection. This necessitated the evening work, as well as going out at 6am the next morning to remove the bags, as if they were left on in the daytime they would severely limit gas exchange, and choke out the plant.
So 8 hours later I rolled out of bed, and Beth and I headed back to the vineyard to pull off bags before the sun got too high in the sky. It only took about an hour, and then we headed home for another hour to shower, or in my case, nap, before coming back in to work. We finished up the day preparing for next week’s similar inoculation of the ‘Horizon’ x ‘Illinois 547-1’ population, and for the rest of the week we worked on preparing inoculum and propagating fungus.
Note: since Bruce and Beth aren’t complete slave drivers, I get to leave early on Friday’s, to make up for working late.