Bad Fungi in Vegetable & Fruit Crops

There Are Good And Bad Fungi in Vegetable & Fruit Crops. Most Are Good But This Article Is About The Bad Ones. Read More Here.

I read so much about Bad Fungi in Vegetable & Fruit Crops but we should never forget that most do far more good than harm. And without fungi rich, biodiverse soils, just wouldn’t exist.

Carnivorous fungi, Oyster Mushrooms — Carnivorous Fungi, Oyster Mushrooms

So let’s look at the facts. . One gram of soil can contain several billion bacteria from thousands of different species and almost as many fungi. Soil teems with fungal life.

The best estimate suggests that there are between 2.2m and 3.8m species of fungi on the Earth – as many as 10 times the estimated number of plant species – meaning that, at most, a mere 8% of all fungal species have been described. Of these, only 358 have had their conservation priority assessed on the IUCN red list of threatened species, compared with 76,000 species of animal and 44,000 species of plant. Fungi, in other words, represent a meagre 0.2% of our global conservation priorities.
https://www.resilience.org/stories/2020-10-20/why-the-hidden-world-of-fungi-is-essential-to-life-on-earth/

Only a small proportion of fungi cause problems in the garden. Of course they cant be ignored but we need a sense of proportion and understand that fungi are vital for plant growth.

Here are some “bad” fungi facts

Most “bad” fungi are invisible to the naked eye.
The World Health Organization published its first list of fungal pathogens in October 2022, warning that certain strains have acquired resistance to known antifungals.

Fungal diseases affect 168 crops listed as important in human nutrition by the Food and Agricultural Organization of the United Nations, and growers worldwide lose between 10% and 23% of their crops to fungal disease every year. That’s a fact not to be ignored. But fortunately as gardeners we suffer somewhat less, though we wouldn’t say the if we get tomato or potato blight (technically these blights are caused by an Oomycete, which is fungi like but not actually a fungus.).

Adaptive potential unleashed

In 2019 fungi dominated the first to sixth places for diseases affecting the world’s 5 most important calorie crops, including wheat, bananas and coffee, which generate revenue that is used to purchase calorie crops.

Fungi are hugely effective pathogens that produce massive amounts of spores. These spores can travel between continents and promote disease spread within and between adjacent fields. So the idea that not growing a crop for a few years will prevent many fungal diseases is flawed.

Fungi exhibit a phenomenal degree of genetic variation and plasticity, which can be generated through mutational changes conferred by transposable elements, mitotic (asexual) recombination and the horizontal transfer of genetic material.

A perfect storm

Current problems have arisen because the adaptability of fungi has met modern agricultural practices. This has led to the emergence of fungicide resistance.

The global fungicide market is expected to grow by 4.9% per year between 2021 and 2028.

A question remains whether fungal diseases will be affected by climate change. Increased temperatures in the Northern Hemisphere may drive the evolution of new temperature tolerances in fungal pathogens. It will provide conditions that inhibit some fungi and encourage others.

Increasing temperatures might affect interactions between plants and their microbiomes, including endophytic fungi, which could become pathogenic as plants change their physiologies in response to environmental stresses.

Early promise

Better protecting the world’s crops from fungal disease will require a more unified approach than has been achieved so far, with closer collaboration between farmers, the agricultural industry, plant breeders, plant-disease biologists, governments and policymakers, even philanthropic funders.

A molecule that targets several processes in the pathogen has been discovered by an inter-disciplinary research team at the University of Exeter, UK. This molecule provides significant crop protection against Septoria tritici blotch in wheat, rice blast in rice and Panama TR4 disease in bananas.

Planting seed mixtures that combine several crop cultivars carrying different resistance genes could slow down pathogen evolution. This collaborative venture could reduce the spread of disease and the erosion of crop-resistance genes.

Artificial intelligence, satellites, remote- sensing tools, incentives to persuade farmers to report disease, and community-science projects that engage the public in the reporting of plant diseases are helping to engender more effective surveillance of fungal disease.

Data collected through AI, community-science projects and so on could be integrated with disease records and climate data to build models that predict when and where plant fungal diseases will occur.

Conventional plant-breeding practices involve introducing one or two genes that confer resistance to a particular disease, known as R genes. However, incorporating two or more R genes can broaden resistance to a diversity of pathogens.

Most R genes encode proteins with a nucleotide-binding site and a leucine-rich repeat region. Pattern-recognition receptors (PRRs) are an earlier detection system for pathogens, and could be combined with new R-gene-edited cultivars or through R-gene pyramiding using conventional breeding to provide more durable and broader resistance to major pathogens. However we are wary of using artificial genetic manipulation of plant genes for good reason.

Biologics are products derived from living organisms, and are being explored for use in crop protection. These include using living antagonists of plant pathogens, and spraying crops with natural antimicrobial compounds. This builds on natural processes. Another natural process is to utilise biointensive gardening systems.

Indigenous knowledge is key to sustainable food systems. New methods for profiling microbes have revealed the existence of beneficial microbial networks, which can be used to create consortia of microbes that promote plant growth and enhance disease protection.

Researchers have found that RNAs from grey mould fungi can silence plant host genes involved in immunity, and that plant hosts can also dispatch vesicles to suppress fungal virulence genes. These naturally occurring RNAi based trafficking systems are now being harnessed to protect crops against fungal disease.

Several studies have documented the efficacy of RNAi in providing resistance to common fungal pathogens, but questions remain about their stability.

A global body for plant health

The UK Research and Innovation (UKRI) council spent US$686 million on COVID-19 research between 2020 and 2023, and $30 million on fungal crop research. The UKRI is arguably just as crucial to human health as medicine and health-care providers.

The International Plant Protection Convention is less well known than other bodies that deal with threats to human well-being.

Because viruses and bacteria dominate as agents of human disease, they have received much more attention than have fungi. Yet fungi are by far the most important agents of disease in crops.