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Botrytis: How On-Site Diagnostics Can Support The Wine Industry
Botrytis bunch rot is a disease that still afflicts the wine industry. An estimated 25% of the globe’s $66 billion worth of wine grapes produced annually lost due to this disease! This article provides an in-depth look into how Botrytis adversely impacts the wine industry and solutions.
Introduction to Botrytis and Wine Industry
The global wine market is economically important, with an estimated value of $340 billion in 2021 and forecasted to be worth $457 billion in 2028. This represents a compound annual growth rate (CAGR) of 4.3%. The process surrounding grape harvesting and wine production has been sophistically refined over centuries, to deliver superior yield and taste.
However, despite these improvements, Botrytis bunch rot is a disease that still afflicts the wine industry. An estimated 25% of the globe’s $66 billion worth of wine grapes produced annually lost due to this disease! This article provides readers with an in-depth look into how Botrytis adversely impacts the wine industry, existing hurdles faced by viticulturists, and how on-site diagnostics are a solution for this established yet burgeoning industry.
What is Botrytis Bunch Rot?
Botrytis bunch rot or grey mould (gray mold) is caused by Botrytis cinerea, one of the most globally prevalent plant pathogen and post-harvest storage rots. The fungus is reported to infect over 200 plant species and causes global annual crop losses between $10 billion and $100 billion.
Within the UK horticulture sector, Botrytis bunch rot is the second largest cause of crop loss, reducing harvest yields and the produces’ marketability. The total cost to the UK horticulture industry is estimated to be £54million. This pathogen is so prevalent because of its capacity to infect plants under a wide range of climatic conditions.
Nevertheless, Botrytis is known to favour mild and wet climates; therefore, able to exploit the severe conditions brought about by climate change. To make matters worse, climate change has, in recent years, adversely impacted global agricultural output, including the wine grape industry. Making this pathogen not only agribusiness, but also a national food security issue.
How Does Botrytis Bunch Rot Impact the Wine Industry?
Botrytis bunch rot in grapes is a major disease worldwide, affecting both wine production and table grape harvesting. Depending on climate conditions, losses for vineyards can range from 15% to 40%, with the cumulative global losses being in excess of $16 billion per year.
This problem is exacerbated by the escalating consequences of climate change, with wine and grape producers warned there is ‘no vaccine’ for combatting the disease.
A blight on wine quality
Botrytis’s adverse impact on the wine industry can be attributed to it degrading wine quality or, more specifically, its taste. For this reason, harvested wine grapes’ ‘Botrytis concentration’ is an important quality marker.
The threshold varies depending on the type of wine; red wine can tolerate grapes that are up to 10% botrytised without affecting its taste. Wineries often impose a price penalty if the concentration exceeds a pre-defined threshold, often 3%-5% due to the potential detrimental impacts the mould can have. However, for sparkling wines, increasing Botrytis infection has differing detrimental effect: it adversely impacts how the wines’ bubble foams.
It is therefore crucial for viticulturists to be able to objectively assess Botrytis concentration on their crop, in order to achieve commercial success. But the process of detecting this pathogen, at present, isn’t so simple.
Difficulties wine farmers face
A major issue facing wine farmers is the difficulty in detecting Botrytis on vineyards with existing diagnostic tests. When examining wine grapes on the field, they may look healthy on the surface; however, the infected grapes could either be in pre-symptomatic phase, or the disease has already afflicted the harvest, but carefully concealed within the bunch.
Viticulturalists at have no choice but to pick the grapes, bring the harvest back to the winery, then utilise diagnostic tests to estimate Botrytis infection level. To further complicate the detection process, traditionally the best industry practices have been lab based, which are both time consuming and face various limitations.
For example, assessing Glycerol, Acetic acid and Gluconic acid (or laccase activity) concentration can provide an indicator of fungal infection, but are not specific to Botrytis. Similarly, Ergosterol levels signify fungal biomass, but not exclusively Botrytis due to naturally occurring yeast species on the surface of the grape berry which contain ergosterol.
Furthermore, despite offering benefits in fungus detection, investigations using quantitative PCT (qPCR) have demonstrated variable results and poor quantification, as a result of the nature of the fungus, which is multinuclear and highly irregular.
The means to accurately detect Botrytis in wine grapes at present are far from optimum for farmers, due to existing logistical and technical constraints. Farmers require diagnostic tests that can be used on-site that are cost-effective, accurate and delivers results quickly.
Adverse impact on wider horticulture sector and human health
Detecting Botrytis isn’t only crucial in maintaining harvest yields, but also important in terms of protecting the wider horticulture sector and human health. As previously mentioned, it is one of the most common plant pathogens, and able to produce high quantities of spores, which can result in rapid plant-to-plant transmission. This could potentially reduce a locality’s overall agricultural yield.
Furthermore, despite being at a lower concentration than other more prevalent fungal spore allergens (such as Cladosporium and Alternaria), a substantial number of people are allergic to Botrytis. Exposure to Botrytis spores, particularly in occupational settings, such as greenhouses, grain mills and vineyards have been linked to increased incidence of asthma and respiratory issues.
The health implications are particularly significant for immunocompromised individuals, where exposure has been shown to escalate into pulmonary Botrytis infection.
Botrytis Alert: GADx (Formerly Mologic) Innovative Solution for Wine Farmers
“As for the treatment of human diseases, early intervention is key for the health of our crops […] BotrytisAlert, facilitates a better informed and earlier intervention to address many of the crop losses caused by this infection.”
Dr Alison Wakeham, Project Leader, Global Access Diagnostics (GADx)
Responding to crop and post-harvest losses due to Botrytis, and the inadequacy of existing diagnostic technology, Mologic developed BotrytisAlert. This is a simple, accurate and cost-effective rapid test that enables wine farmers to detect Botrytis without the issues associated with existing diagnostics on the market.
What differentiates BotrytisAlert is that it provides wine farmers with an objective measure of Botrytis outside of a laboratory setting. For the first time farmers can specifically and rapidly detect this plant pathogen at the exact source on the vineyard.
Being able to quantify grey mould contamination in real-time empowers wine grape growers, agronomists and scientists to objectively intervene and prevent later polycyclic disease epidemics and post-storage rots.
The efficacy of BotrytisAlert was made clear in a 2021 study by Charles Sturt University for Wine Australia. Having analysed Mologic’s lateral flow test, the report’s author made clear: “It is recommended that this technology should be adopted for the assessment of grey mould contamination of wine grapes.”
The study also emphasised the test’s versatility and made clear it is also “applicable to other horticulture industries.” BotrytisAlert’s capacity to deliver rapid, accurate results on-site makes the test an invaluable asset for the wine and wider horticulture industries.
Early detection and quantification of Botrytis not only yields dividends in financial terms for the wine industry, but essential means towards food security due to climate change. This is not an issue exclusive to the wine industry, but the entire global agricultural sector. As a social enterprise and leader in rapid diagnostics, GADx is committed to its mission of providing affordable and quality diagnostic tests for philanthropic causes.