Vegetable growers across the UK have faced a difficult start to the spring, as cold temperatures over winter have left sprouting broccoli crops severely damaged. At Wakelyns Agroforestry in Suffolk, a rather unusual crop of broccoli plants has weathered the storm.
Casting an eye over the broccoli field at Wakelyns, an onlooker might hesitate to believe it is all the same brassica. Certainly, these plants challenge assumptions about what a sprouting broccoli crop looks like: some plants are tall and sparse while others are low-growing and bushy; leaves may be smooth and spreading or have tightly curled edges; and colours range from yellow-green to dark purple.
The 200 plants are part of a trial being run at Wakelyns Agroforestry which is part of the Solibam project, a pan-European collaboration which aims to harness the advantages of diversity in all aspects of farming.
The trial compares the performance of diverse populations of landrace broccoli (closer to its wild relatives than commercial varieties) with that of a uniform commercial line, and also compares more diverse populations with less diverse ones. The broccoli plants are being grown on sites in France, Italy and England for three generations, where their health and output will be closely monitored in an attempt to establish whether diverse populations are better at adapting to different sites and different weather conditions than uniform lines grown from commercial seed, particularly in the context of low-input conditions. It is hoped that diversity will improve yield stability.
As the broccoli reaches maturity, interesting results are already beginning to emerge. In addition to growth form, leaf shape and colour, there is tremendous variability in the survival rate and size of the plants. Some have flourished into leafy abundance whilst others have succumbed to pest attacks or frost damage. The landrace populations include plants at both extremes, whereas the commercial seed drilled alongside as a comparator has performed much more consistently, producing plants which underperform the best of the populations but outperform the worst.
One interesting implication of this genetic and phenotypic variability for growers is the possibility of using populations for on-farm selection and seed-saving. With such a wide range of genotypes at his or her disposal, the grower could theoretically develop their own unique line from broccoli which performs well on his or her site and produces a crop specifically suited to market needs. For example, an organic grower with a bad slug problem might select for thick-leaved plants unpalatable to herbivores; or, a grower reliant on very local retail channels who is not able to sell high volumes of crop at one time might want to breed a population with diverse maturation times, yielding small quantities of crop continuously over a long period.
It is difficult to breed and seed-save from brassicas because of their high outcrossing rate, so at present there are few growers who invest in it. Recent years, however, have seen some resurgent interest in localised breeding from growers hoping to regain control over their seed resources and the traits associated with them.
The Solibam broccoli trial aims to develop a practical and cost-effective on-farm breeding strategy which will deliver consistently good results and which could even allow for the development of ‘speciality’ broccoli lines with a unique selling point. Adjacent to the agronomic trial described above, plants have been set aside for a breeding trial which aims to develop a locally adapted line within three years.
The most immediate challenge facing researchers as harvest time approaches is marketing. Consumers of purple sprouting broccoli in the UK are used to buying a bundle of stems uniform in colour and texture. The landrace populations are likely to deliver a much more multicoloured product which tastes somewhat different to the mainstream purple sprouting broccoli varieties available here. Consumer reactions will be tested at farmer’s markets in East Anglia when harvest time arrives, and the researchers await results with both excitement and trepidation.
The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under the grant agreement n° 245058.
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