It is traditionally a seasonally-restricted fruit in Britain, a cream-coupled treat synonymous with summer sunshine and Wimbledon fortnight. However, although greenhouses and import have conferred the ever-popular strawberry with virtually continuous availability, supply and cost remain weather-dependent. By contrast, an advantageous combination of sub-tropical latitudes and elevations enable year-round growth in Brazil, the largest strawberry producer in South America.
Exploitation of vast areas of agriculturally-convertible land has facilitated Brazil’s remarkable transformation from large net food importer just four decades ago to largely self-reliant, major producer/exporter today. However, developing and maintaining large-scale crop harvests inevitably brings increased susceptibility to insect pests and phytopathogenic microorganisms (such as bacteria and fungi). Strawberries are vulnerable to gray mould or gray rot, the result of infection by Botrytis cinerea, an important fungal pathogen, which attacks over 200 known plant species, and is a particular problem for greenhouse crops.
In order to displace the indiscriminate application of fungicides, and the consequent contamination of ecosystems and increased selective pressure for resistant strains, there are increasing moves towards the identification and isolation of novel biological compounds for application in transgenic crops and non-toxic agrochemicals. And Brazil, whose recent agricultural success story is founded on hard research, is proving no slouch here either. Addressing the global problem of gray rot, researchers at the Universidade Católica de Brasília have recently isolated two novel proteins from flowers of the rosemary pepper, Lippia sidoides, traditionally recognised for its antimicrobial and anti-inflammatory properties. And, as reported in The Protein Journal*, these proteins demonstrate potent antifungal activity.
Of note, these antifungal proteins were isolated from petals and sepals, an extremely difficult procedure due to the low proteinaceous content of these flower tissues. Combining chromatographic and electrophoretic techniques to separate proteins by chemical properties and size, the initial crude extract was progressively processed into a fraction containing two discrete proteins. Sequence analysis revealed similarity to a group of proteins with known involvement in plant disease resistance, being essential for phytopathogenic response. Hence, the fraction containing these two proteins was evaluated for effect on microbial growth. Whilst no inhibitory activity was observed against any of the bacterial species tested, growth of the mould B. cinerea was substantially reduced, an effect greater than that produced by a common chemical fungicide. Attribution of this effect was confirmed by comparison with the isolated proteins, named Ls-AMP ( L. sidoides anti-microbial protein) 1 and 2, confirming for the first time the antifungal activity of members of this protein family.
These two proteins thus represent a novel class of antifungal proteins, isolated from the flowers of rosemary pepper. This important property lends itself to the generation of B. cinerea-resistant transgenic plants, and a reduced reliance on chemical fungicides. This will likely be acceptable to Brazil, the world’s second largest user of genetically-modified plants after the USA. Whether strawberry-loving, but GM-recalcitrant Britain will embrace such knowledge, however…
*Moreira JS, Almeida RG, Tavares LS, Santos MO, Viccini LF, Vasconcelos IM, Oliveira JT, Raposo NR, Dias SC, & Franco OL (2011). Identification of Botryticidal Proteins with Similarity to NBS–LRR Proteins in Rosemary Pepper ( Lippia sidoides Cham.) Flowers. The Protein Journal, 30 (1), 32-8 PMID: 21210197 DOI: 10.1007/s10930-010-9299-4