Statement – towards the end of 2024 we stated that our desire was to move to a new platform, after being with WordPress since 2016. (9 years) We have the new platform and already have been posting articles there. A platform where journalists and academics can post their content with ease. The platform is Substack.com – Taiga Bonzai.com we will post this article on WordPress then we will cease.

Hi welcome to Taiga Bonzai, in this article we revisit the article 62 – ‘New diseases’ 2 due to the comments received and the request for further information.

Introduction – the above mentioned article focussed it’s attention on Fusarium solani, a complex species of at least 26 closely related filamentous fungi in the division Ascomycota, family Nectriaceae. It is the anamorph of Nectria haematococca and a common soil inhabiting mold.

Fusarium solani is implicated in plant diseases as well as in serious human diseases such as fungal keratitis (Summerell, Brett A.; Laurence, Matthew H.; Liew, Edward C. Y.; Leslie, John F. (14 September 2010). (“Biogeography and phylogeography of Fusarium: a review.“)

History and taxonomy – the genus Fusarium was described in the 1930s, by Wollenweber and Reinking who organized the genus Fusarium into sections, including Martiella and Ventricosum, Lesli, John., Summerell, Brett, A. (2006) ^{The Fusarium Laboratory Manual. Ames: Blackwell. pp. 250–254.}

In the 1940s, these were collapsed together by Snyder and Hansen to form a single species, Fusarium solani; one of nine Fusarium species they recognized based on morphological features. 

The current concept of F. solani is as a complex species consisting of multiple, closely related and morphologically poorly distinguishable, “cryptic” species with characteristic genetic differences. There is a proposed concept for the entire genus – widely subscribed by specialists – that would include this complex. (Geiser, David M; Al-Hatmi, Abdullah; Aoki, Takayuki; Arie, Tsutomu (2020-11-17)

Like other species in its genus, Fusarium solani produces colonies that are white and cottony. However, instead of developing a pink or violet centre like most Fusarium species, it can become blue-green or bluish brown. (as shown below) 

On the underside, they may be pale, tea-with-milk-brown, or red-brown. Yet, some clinical isolates have been blue-green or ink-blue on the underside. Colonies are low-floccose, loose, slimy, and sporadic. When grown on potato dextrose agar (PDA), this fungus grows rapidly, but not as rapidly as Fusarium oxysporum. In PDA, F. solani colonies reach a diameter of 64–70 mm in 7 days.

F. solani is found in soil worldwide. However, a given species within the complex may not be as widespread and may not have the same ecology as others in the complex. In general, as a soil fungus, F. solani is associated with the roots of plants and may be found as deep in the ground as 80 cm. It is frequently isolated in tropic, subtropic, and temperate locations, and less frequently isolated from alpine habitats. 

The pH of soil does not have a significant effect on F. solani, but soil fumigation causes an increase in occurrence. F. solani is typically sensitive to soil fungicides. F. solani has been found in ponds, rivers, sewage facilities, and water pipes. 

F. solani has it’s chlamydospores that overwinter on plant tissue/seed or as mycelium in the soil. The pathogen enters the host through developing roots, where it can infect it. After infection, F. solani produces asexual macro and microconidia which are dispersed via the elements. The pathogen can persist in the soil for a decade and if left unchecked can cause complete crop loss.

The fungal pathogen rots the roots of its host plant. It also causes soft rot of plant tissues by penetrating plant cell walls and destroying the torus. It is implicated along with Pythium myriotylum, in pod rot of the pods of groundnuts. 

It can cause damping off, corn rot, and root rot, as well as sudden death of soybeans (SDS). It is a very generalistic fungal species and has been known to infect peas, beans, potatoes, and many types of cucurbits. Symptoms include general plant decline, wilting, and large necrotic spots on tap roots. Recently the pathogen has also done serious damage to olive trees throughout the Mediterranean region.

F. solani is largely resistant to typical antifungal agents. The most effective antifungals in treating F. solani infections are amphotericin B and natamycin; however, these agents have only modest success in the treatment of serious systemic infection.

Effect on humans – as of 2006, there has been increasing evidence that F. solani  can act as a causal agent of mycoses in humans, it has been implicated in the following diseases: disseminated disease, osteomyelitis, skin infection, fungemia, and endophthalmitis. 

Half of human disease involving Fusarium is caused by F. solani and is involved in most cases of systemic fusariosis and corneal infections. In immunocompromised patients, F. solani is one of the most common agents in disseminated and cutaneous infections.

In the southern USA, fungal keratitis has been most commonly caused by F. solani, as well as F. oxysporum. Cases occur most frequently during harvest season as a result of corneal trauma from dust or plant material. Fungal spores come into contact with the damaged cornea and grow.

Without treatment, the hyphae can grow into the cornea and into the anterior chamber of the eye.^] F. solani is also a major cause of fungal keratitis in HIV positive patients in Africa.

An investigation into a meningitis outbreak of 79 cases since October 2022, that had killed 35 people (34 of them women who had undergone cesarean section) in Durango (Mexico city) revealed the contamination of bupivacaine with Fusarium solani in 4 batches, used by an anesthesiologist.

As of June 1, 2023, a multistate outbreak of meningitis due to F. solani was ongoing among patients who underwent epidural anesthesia at two clinics in the Mexican city of Matamoros, Tamaulipas a Mexican state, with a total of 212 residents in 25 US states identified as being at risk, two of whom had died.

There will be more scholarly on new plant disease be it fungal pathogens borne on the wind or wing, or via entomology invasion. We will continue to add them on our new platform Substack.com where you can find us using our name Taiga Bonzai.com. We thank our readers and followers from around the world whom have been with us since 2016, until next time, BW, Nik.