Rust Fungi and Dr. Robert Park

Rust fungi, also known as Pucciniales, are a group of plant pathogenic fungi that infect many important crop plants, including wheat, corn, soybean, and barley.

They are so named due to the characteristic orange-brown rust-like pustules that appear on the leaves, stems, and other above-ground parts of the infected plants. These pustules are composed of masses of fungal spores, which can be easily dispersed by wind, rain, or insects, facilitating the spread of the disease.

Professor Robert Park’s career began after he completed a Ph.D. in Plant Pathology at La Trobe University in 1984. His first appointment was with the Queensland Department of Primary Industries, where he worked on the impact of wheat stripe rust in the northeastern Australian wheat belt. Professor Park is particularly interested in the way in which fungal rust pathogens evolve and acquire virulence for resistance genes in their hosts.

He has conducted Australia-wide race analyses for the rust pathogens that cause stem rust in wheat, leaf rust in wheat, leaf rust in barley, and crown rust in oats, since 1988. This work has involved analyzing more than 10,000 rust samples from farmers’ fields, led to the identification of more than 160 new cereal rust pathotypes, and has clearly demonstrated the increasing frequency of exotic rust incursions into Australia.

His research group has developed and applied DNA-based markers to understand how rust pathogen populations have evolved in Australia over the past 100 years, and are now applying whole genome sequencing to delve further.

All rusts are obligate parasites, meaning that they require a living host to complete their life cycle. They generally do not kill the host plant but can severely reduce growth and yield. Cereal crops can be devastated in one season; oak trees infected in the main stem within their first five years by rust often die. The spores of rust fungi may be dispersed by wind, water or insect vectors. They may also be transported by humans. They will collect on clothes, and if unwashed, can make their way to other fields.

The rust life cycle begins in the spring, when a spore lands on the alternate host. This spore germinates and – under the right conditions – infects the alternate host. Both the spore and resulting mycelium^[1] have only one complete copy of chromosomes. Once the rust has established itself, it produces spores called spermatia on a structure called spermagonium. Insects and wind will distribute them quickly where spores of different mating types have the opportunity to interact.

In the next stage, the mycelium quickly sets about producing spores. The following stage is the most important in rust’s life cycle. The rust aggressively infects its primary host, spreading within the host’s tissues as well as between hosts.

Starting soon after infection and lasting until the end of the primary host’s growing season. In the final stage, towards the end of the primary host’s growing season, the rust starts producing teliospores, which are now called “telia.”

Teliospores are thick-walled spores that cannot infect any plants but are designed to survive winter. In the spring, each teliospore germinates and produces a structure. These spores are carried by the wind to the rust’s alternate host to begin the cycle anew.

Professor Park has delivered short courses on rust pathology and genetics to undergraduate students and is regularly involved in international training courses in these areas. He has supervised 27 Ph.D. students and 6 Masters students, who have conducted research principally on cereal rusts but also on cocoa genetics and the myrtle rust pathogen.

Robert’s postgraduate teaching and training have had great global reach and have had a strong focus on gender with 6 of the 11 new scientists recruited into his program and 14 of the 32 postgraduate students he has trained being women. He has received many awards including the Friendship Award of China (2009), the supreme award that the Chinese Government confers to foreign experts who have made outstanding contributions to China.