Graduate students
contribute to potato research

DR STEVE MILRO Y
POTATO RESEARCH WA, MURDOCH
UNIVERSITY

Potato is a crop of global importance, so it is not surprising that the potato research at Murdoch University is attracting the interest of post graduate applicants from a number of countries.

While the students are here training, they make an important contribution to research in areas that are important for the local industry. We currently have four PhD students with research projects in potato: Ni Nguyen and Diem Nguyen are now over half way through their research programs while Hassan Sardar and Iqbal Hossain are in the first six months of their time here.

Improving post-harvest quality
Both Ni Nguyen and Diem Nguyen are studying the use of molecular biology to develop lines with improved post-harvest quality. While this has been done before, our aim is to do it using new approaches that will not result in a GMO.

Bruising can be a major cause of product loss during harvest or post-harvest transport and processing. When bruising occurs there is a mixing of compounds from different parts of the cell.

The dark colour of a bruise is caused when oxidation products react with amino acid compounds in the outer few millimetres of the tissue. The oxidation processes leading to the dark pigments rely on an enzyme called polyphenol oxidase (PPO). Ni Nguyen is working to down regulate the genes that control the production of PPO. This is expected to dramatically reduce susceptibility to bruising. It will be of particular value for exporting potatoes
by sea to markets in Asia.

There are a number of challenges in this project. Most significantly, there are six different genes that regulate the production of PPO in potato with four believed to be important in the tuber. Therefore, rather than manipulating the expression of one gene, Ni needs to work with at least four. Further, Ni is working with three varieties that show a range of levels of susceptibility to bruising. Awkwardly, the genes differ slightly between the genotypes. This has presented a challenge for identifying the exact points on the chromosome that need to be manipulated. Ni has successfully negotiated this challenge and we are now looking forward to the first new lines in the tissue culture facility.

The research of Diem Nguyen, also on aspects of post-harvest quality, has a component that is commercially sensitive and so will not be discussed here.

Nematodes and biofumigation
In recent decades, there has been an increasing interest in the use of biofumigation for disease control. With a number of nematicides being withdrawn from the market, interest has also been expressed in the potential for biofumigant crops to contribute to the management of nematodes as
well as soil borne diseases. Indeed some biofumigant varieties have been specifically developed for this purpose. However, the impact of biofumigants appears to be highly variable.

Iqbal Hossain has a Master’s degree in nematology from Ghent University in Belgium. The first part of his PhD research plan is to survey potato growing areas in WA to identify which nematode species are most common and where they occur.

While we know a number of the species which are causing damage, there has not been a systematic study of the species present in our horticultural areas.

The second part of his study will be to measure the concentration, distribution and persistence of key ITCs in the soil after a biofumigant crop. Finally, he will examine the impact of the chemicals, not only on nematode mortality but on their ability to move, to identify their
host, and on their reproduction rate. It is possible that after a biofumigant crop has been grown, the concentrations of ITCs in the soil might not be high enough to kill nematodes, but could still play a useful role in slowing the development of populations by interfering with their feeding and reproduction.

Temperature adaptation
As part of his PhD project, Charles Obiero examined the climatic records for the potato-growing regions in WA. As expected, average temperatures showed a consistent increase.
Importantly, Charles also showed an increasing frequency of episodes of temperatures that are likely to impair yield. This emphasises the need to identify management practices to reduce the impact of high temperature and to identify varieties that are better adapted to high temperature.

While various studies have shown that varieties respond differently to high temperature, there has been less work done to identify the mechanisms that allow some varieties to perform better under high temperature. In his PhD, Hassan Sardar will screen a number of
varieties currently grown in WA to test for variation in yield response to an episode of high temperature. He will then select tolerant and susceptible varieties and look at how growth processes differ between them when exposed to high temperature. The aim is to develop a
reliable way of screening new cultivars for their likely performance in hot conditions using a sound physiological basis. The results are also likely to improve our understanding of the
mechanisms of the impact of heat and so strengthen the basis for developing management strategies for high temperature. In the longer term the work may contribute to the development of more heat-tolerant varieties.