What prompted your current research?

I was born and raised in a small town in Gunma Prefecture called Numata. My parents are farmers who grow blueberries now, but at that time were growing konjac and peonies. Because I was the eldest son of five brothers and sisters, I enrolled in Chiba University’s Faculty of Horticulture, the same place that my father went to, with the aim of eventually taking over the family farm. It was there that I met a professor whom I much respected, a researcher in horticultural crops, and I developed a strong interest in research myself as a result. After graduating, I was lucky to find a job at Experiment Farms in Hokkaido University.

Figure 1. Haskap berries. Ready to harvest around July.

So while I didn’t end up taking over the family farm, I do want to conduct research in areas as close as possible to agricultural production. In my first year at Hokkaido University, I came across berries known as Haskap (blue honeysuckle, Lonicera caerulea), that are native to Hokkaido (Figure 1). I tried some, and found them to be really delicious. But there are also haskap that taste awful, so bitter that you want to spit them out immediately. I was fascinated by this inconsistency and variation (diversity), and decided to study this plant and see if I could breed some cultivars with improved traits.

 

What kind of research are you carrying out?

When I ask people what they think of Haskap, even farmers producing them say they’re bitter or too sour, and complain that their small size makes harvesting them very tough. If you choose a bush that produces tasty berries and eat only fully ripened berries, they have a very fruity aroma and taste really delicious, a perfect mix of sweet and sour, but I think there’s still room for improvement. The small size of the berries does indeed make them laborious to harvest. This points to a need to increase their size. And since taste varies considerably by bush, it’s also important to select bushes with good-tasting fruit.

Breeding requires collecting and evaluating the plants that you plan to use as your raw material. So the first thing I did was to collect Haskap bushes growing in the wild all over Hokkaido and analyze their traits. I collected bushes from Mt. Yokotsudake near Hakodate, Kushiro Marsh, Bekanbeushi Marsh, Kiritappu Marsh, Betsukai, Shibetsu Marsh and other locations as well as Tomakomai’s Yufutsu Wilderness, which is Hokkaido’s largest natural habitat for Haskap. So far, worldwide distribution of haskap has been studied by Russia’s Professor Plekhanova, who reported the existence of two groups in Eurasia that differ according to the number of chromosomes they have, one group being diploid with 18 chromosomes, the other tetraploid with 36 chromosomes. So, what can we say about the chromosomes of the Haskap bushes I collected from various parts of Hokkaido? I used an instrument called a flow cytometer to carry out this analysis. It enables us to distinguish the ploidy (a term that indicates the number of sets of chromosomes present, e.g. diploid for 2 sets, tetraploid for 4) of the plant from just one leaf in a few minutes. Investigating the ploidy of Haskap growing wild in Hokkaido produced some interesting results. Firstly, I found that there are both diploid and tetraploid Haskap in Hokkaido. I also discovered that diploid plants are found growing in Kushiro Marsh and Bekanbeushi Marsh in eastern Hokkaido, but those growing in other locations are all tetraploid.

Tetraploid plants can arise from diploid plants by natural doubling and other means, but we have yet to discover a mechanism whereby tetraploid plants can give rise to diploid plants. This suggests that Hokkaido’s Haskap originated in the eastern region of the island. My hypothesis is that, in the long distant past, diploid haskap gave rise to tetraploid individuals that spread to various parts of Hokkaido because they were better able to grow in a range of different environments.

But where did Japan’s Haskap come from originally? I’m currently working with researchers from China, Russia, and America to start research on a worldwide comparison of Haskap. For this comparison, we are using phylogenetic systematics based on DNA sequences (a method for determining how close different individuals are from similarities in their DNA sequences). This method enables the comparison of Haskap from various locations with a high degree of precision. We are also examining ploidy using flow cytometers. Recent research has shown that there are other Haskap polyploids, in addition to diploids and tetraploids.

 

What do you plan to do next?

Figure 2. A hybrid between haskap and Lonicera gracilipes var. glabra with berries that are sweet and tasty

I hope to apply the research results we’ve obtained so far on wild Haskap to the actual breeding of new cultivars. For example, the ploidy that we’ve found in Haskap is of great significance to breeding such cultivars. In principle, you can expect the tissues and organs of plants to increase in size as their ploidy increases. Also, you can breed individuals of intermediate ploidy by crossing those with different ploidy. Therefore we’re conducting research that involves manipulating ploidy to produce cultivars with large berries.

As part of our attempts to develop good-tasting Haskap, we have bred interspecific hybrids (Figure 2) between Haskap and Lonicera gracilipes var. glandulosa or L. gracilipes var. glabra, two varieties of a closely related species that produces small sweet-tasting red berries.

In our research group, we look for plants growing wild in Japan that might be useful to breeding. In addition to Haskap, we are looking at raspberry and other plants. I enjoy doing fieldwork that involves searching for and investigating plants, but I’m also interested in biotechnology that involves the use of microscopes. I hope that our studies will lead to the creation of new cultivars homegrown at Hokkaido University.