Today started not much different from yesterday. That said, Moquegua is much nicer in morning rush hour than Arequipa, but as soon as we left the city we hit the desert. Everything was flat and sandy again for miles and miles. Like yesterday, the almost straight Panamerica Sur motorway only made a couple of turns when we were nearing one of the two rivers that had to be crossed. After about 1,5 hour, we made it to the 3rd river and the city of Tacna. From here we went back in the mountains. Just like yesterday, the first 20 kilometers were still too low and too sandy, but as soon as we gained elevation and the rocky riverbed came closer to the road, S chilense appeared as well. We drove up to 3500 m and then went down on the other site. What we saw there was quite unexpected. After so many day with mainly sand,we were suddenly looking into a valley where many parts were green.

We decided not to sample at all on the way up, but to drive for another two hours from Tacna to a town called Tarata. (To keep things simple, yesterdays furthert point was a town called Torata). Together with Aurelien Tellier and other collaborators, I have worked on the creation of a reference genome for S. chilense. The sequenced plant came from a population with number LA3111 and this population grows on the outskirts of Tacna. However, shortly before we reached Tarata, I realised that our fancy 4×4 had drunk a bit more Diesel on the way up than anticipated. Or differently said, if we continued like this, we would probably not get back to Tacna with this tank of fuel. Our good hope of finding a petrol station in Tarata vanished when we saw how small the village was. To be sure, we asked a police officer and he pointed out that we just passed a Rural Petrol Station. We backed up and realised that indeed the sign was clearly there. Inside we found a couple of barrels with either Diesel or Petrol and a small lady who would happily sell us half a bucket of the first one. We could borrow her funnel to make sure everything ended up in the petrol tank.

With some extra fuel, we drove on and it did not take long until we found a site, or basically two sites that were both equidistant from the estimated coordinates for LA3111. Based on the description, we decided that it must have been the site closest to town. About 5 plants were growing on the left side of the road on the slope overlooking the town and a few others preferred to rocks on the right side of the road. So behold: below the origin of the plant that provided the S chilense reference genome.

After this highlight, we drove a bit further and found that even at 3050 m the Peruvian love their potatoes. A neat little potato field was not far away from this site and on our way down we would realise that there were a few other potato fields not far from (or even very close to) some S. chilense plants. The potatoes appeared to have been sprayed, but there were also some symptoms of late blight visible, thus indicating that it is in the area and can grow well.

On the way back we made a lot of stops and collected as many samples as we could to process back in our hotel in Tacna. I am now debating whether we will change the plan for tomorrow. The original plan was to drive up in another valley to find more S. chilense, but we have a lot of mountain samples and we could also try our luck on the coast. There are no recorded S. chilense specimens on any of the databases, but they could grow there as well. Luckily I have still the whole night to think about this.