On Monday, Beth and I went out to the block of V. rupestris B38 x ‘Horizon’ to rate for disease. To our relief, disease there was!
Now that we have disease, we can phenotype the population, one of the most important steps in creating molecular markers. A phenotype(n.) is a trait of an individual, due to a mix of genetic and environmental factors. As we are looking at the inheritance of black rot resistance in grapevines, our phenotype of interest is disease severity on clusters. We therefore phenotype(v.) the population by rating disease on a 0 to 4 scale
0 – No sign of disease
1 – First sign of disease: a few lesions or starts of lesions on fruit
2 – Few to many lesions on fruit, with no pycnidia formed
3 – Few to many lesions on fruit, some lesions have pycnidia
4 – Tons of lesions with many pycnidia
Rating for disease resistance on the clusters is actually pretty challenging, because you have to check every single berry on the cluster to make sure it doesn’t have a lesion that could bump it up to the next category. It doesn’t sound too hard, but there’s something about the three-dimensionality of the clusters that makes it hard to tell. Also, as you can tell from the classifications, it is a bit subjective. And the ratings take forever. I am not very good at them, but Beth is quite good at it.
Besides the disease ratings, the week was not very productive, because Beth and I both got wiped out by a stomach bug.
On Wednesday I did a few secondary isolations off the second batch of plates I’d made last week. I do this by taking a chunk of of one of the many (different kinds of) colonies on the primary isolation plate, and moving it to a fresh sterile plate where it can be alone. We had better luck with the second batch than the first: a few more of the colonies looked like they could have been black rot. To define whether or not they actually are, we need to analyze the genetics, but that is an activity for a later day.
Editors note: I now only have one week left in the program, and we haven’t had time to do the analysis, so the world may never know. I may as well tell you now, dear reader, so you don’t get your hopes up.