Canola research is flowering

Two separate studies into the oilseed crop canola are providing vital information that will help improve crop yields.

An international genome study, featuring researchers from The University of Queensland (UQ), University of Western Australia (UWA) and Southern Cross University (SCU), has shed light on the historical origins of canola. Published in the journal Science, the study has shown that the ‘polyploid’ species Brassica napus emerged much earlier than previously thought - around 7500 years ago - from the ancestor genomes of B. oleracea (cabbages, cauliflower, broccoli) and B. rapa (turnips, Chinese cabbage).

According to Professor Graham King, the director of Southern Cross Plant Science, “Human cultivation and breeding of B. napus morphotypes may have affected chromosome behaviour and organisation within this timespan, with subtle (epigenetic) changes superimposed on the DNA sequence where genes controlling valuable agronomic traits are located.

“It appears that human cultivation and breeding of this relatively new species may have resulted in selection of ‘cut and paste’ exchanges between the original chromosomes, and that this has affected the interaction between genes controlling valuable agronomic traits.”

Over the past 60 years, the oilseed canola crop has undergone intensive breeding to optimise flowering behaviour, seed oil content and fatty acid composition; decrease nutritionally undesirable erucic acid and glucosinolates; and improve disease resistance. Professor King said, “Having the complete reference genome sequence for canola provides us with an excellent tool to understand the available genetic diversity, to increase yields and reduce use of fertiliser inputs.

“In particular, this new information provides unique insights into the early evolution of a domesticated polyploid and will facilitate the manipulation of useful variation, contributing to sustainable increases in oilseed crop production to meet growing demands for edible oils, biolubricants and other natural products.”

Meanwhile, UWA researchers have discovered the key to understanding what makes Australian canola flower earlier than its Canadian and European counterparts. Plant breeders cannot simply transfer varieties from Canada or Europe into Australia as they flower much too late for the Australian environment.

Associate Professor Matthew Nelson from UWA’s Institute of Agriculture and School of Plant Biology has identified that heat-responsive genes are responsible for flowering time in Australian spring-type and European summer-type canola. He and his colleagues have published their research in the journal PLoS ONE.

“We took a European summer-type canola, crossed it with Monty, a typical early flowering Australian variety, and analysed the progeny for variation in flowering time,” Associate Professor Nelson said.

“There was a huge variation from about 30 days to 160 days in our typical Australian environment. This was totally unexpected and we showed there are several forms of these heat-responsive genes controlling flowering time.”

The research indicated that the European plants required much more accumulated heat (thermal time) to flower than the Australian plants. According to Associate Professor Nelson, this counters the long-held assumption that “long summer days in Europe and Canada triggered flowering, not heat”.

“Understanding this complex process is important as breeders alter the adaptation of crops to a new and changing environment,” research team leader Winthrop Professor Wallace Cowling said. “International canola breeders will use this information to re-establish the correct flowering time in canola when they cross between Australian types and summer annual types in the Northern Hemisphere.

“With increasing global temperatures, or in low rainfall environments, it will be possible to ‘mix and match’ forms of these heat genes to achieve the target flowering date.”