For most of this week, I continued propagating fungus in the lab. However, Thursday the weather was good, so I got to get out in the vineyard to help Bruce’s team prepare to make crosses over the next few days. This work is not directly related to my black rot project, but my other job as a summer scholar is to help out Bruce’s lab in a broader sense, and so I do.
In order to make a controlled cross between two grapevines, we need to assure that no stray pollen can pollinate the flower before we do so. Grapevines have perfect flowers, meaning they have both male parts–the anthers–which produce pollen, and female parts–the pistil–which produce the eggs and eventually will house the developing seeds. On an inflorescence that we will use as a female, therefore, we need to remove all of the anthers from the flowers, in a procedure called emasculation. We emasculate the flowers by removing the anthers from all flowers in a cluster with tweezers, and then putting a paper bag over the cluster to exclude foreign pollen until we can come back a few days later to intentionally pollinate. Closeup of a grape flower.
There are at least as many flowers on an inflorescence as there are grapes on a cluster, and so emasculating each cluster takes us between half an hour and an hour, depending on the size. It’s slow, painstaking, and precise work, but extremely important to do well. After each person finishes a cluster, we have someone else check to make sure we didn’t miss any flowers, because even one anther remaining once we bag the cluster could contaminate the whole thing, and destroy an hours worth of work.
Fun fact: we use the same bags to cover the pistilate (emasculated) flower clusters as corn breeders use to cover the tassel and capture pollen: of course, corn is monecious, having the male and female parts on different parts of the same plant, while grapes have both male and female parts on the same flower.
For a great video of the whole crossing process, check out this video by Bruce and VitisGen, where he explains the whole thing.