Tracking a banana killer in Sumbawa

Who would think of bananas when we talk about endangered plant species? And yet this crop is particularly at risk. The main problem is that a single variety − the Cavendish banana − is almost exclusively cultivated across the globe in huge monocultures. While this form of cultivation is economical, it is also risky, as pathogens can spread like wildfire on the genetically impoverished plantations. In the 1950s, a fungus almost wiped out the predecessor variety Gros Michel, and even today the danger of such a banana apocalypse has by no means been averted.

 

The bacterium Ralstonia syzygii poses a serious threat to banana plantations in Southeast Asia. It has been spreading since the 1980s, initially in Indonesia, and has now also reached the Asian mainland. Infected plants bear shriveled and inedible fruit, and, as the disease progresses, the whole plant withers and dies. Our aim is to use genomic analyses to localize the origin of the pathogen and trace how it has spread. This way, we not only want to better understand the dynamics of the outbreak, but also find alternate or wild host plants. If we can discover the genes making these plants resistant to R. syzygii, we can contribute to breeding new, resistant banana varieties.

 

Locally, I am working with Siti Subandiya, professor at the Universitas Gadjah Mada in Yogyakarta in Central Java, and the plant pathologist Ady Prakoso. Together we collect tissue samples of infected banana plants from various islands in order to isolate and ultimately sequence the pathogen. Siti and Ady aren’t just great scientists and wonderful colleagues − thanks to them, I am constantly learning new things about their home country and its culture. For example, we visited the famous 8th century temple complex Borobudur together, which is located just a few kilometers outside the city. It is the largest Buddhist monument in the world and is a UNESCO World Heritage Site. On another occasion, the two of them organized a batik workshop for us. Working with the fine fabrics, hot wax, and dyes takes time, and requires focus and patience, much like good science.

 

We go out and collect the majority of our samples at the end of the wet season. When everything is green, it is easier to spot infected banana trees with their characteristic yellowish new shoots. This season, we will use motorcycles and drone photography so that we can be more flexible and get around in areas away from paved roads. On the muddy country lanes, collecting trips can quickly turn into a battle with mud and debris. Nevertheless, this way of getting around has proved its worth, and for me there is no better way to get to know the islands. The tropical landscape with its rice terraces is just as inspiring as the open and polite people we meet along the way. Many ask what we are doing and even offer us their help. We have even been invited into people’s homes on occasion.

 

I’ve also spent the last few days on the road on my motorcycle, but this time alone and purely for my own enjoyment. I took a break and traveled to Sumbawa via the island of Lombok. I got caught in a thunderstorm in Lombok yesterday and was completely soaked in no time. After arriving in Sumbawa this afternoon, I was put up in a tiny hotel with just three guest rooms. For dinner I had my favorite dish Ayam Taliwang − grilled chicken in a spicy sauce of coconut milk, nuts, and chili. Now I’m sitting tired and content in my room, looking forward to tomorrow. There’s a well-known surf spot nearby that I want to try out. I’m going to hire a longboard first thing in the morning. In three days, I’m heading back to Yogyakarta, where I’ll meet Siti and Ady. Then we’ll sit down together and plan our next collecting trip. There are still a few blank spots on our map.