The treasure trove of yeast genera and species described by Johannes van der Walt (1925-2011).

Yeast taxonomy and systematics have in recent years been dealt with intensively primarily by a small group of individual researchers with particular expertise. Amongst these was Johannes P. van der Walt, who had a major role in shaping our current understanding of yeast biodiversity and taxonomy. Van der Walt based his taxonomic studies not only on available cultures, but also by going into the field to isolate yeasts from various substrates. This pioneering work led to the discovery of many new genera and species, which were deposited in the Centraalbureau voor Schimmelcultures (CBS) collections for future studies in taxonomy, genomics, and industrial uses. These treasures collected during more than 60 years provide an outstanding legacy to the yeast community and will continue to exist in his absence. This contribution provides a comprehensive overview of the current nomenclatural and taxonomic status of the yeast genera and species introduced by van der Walt during his career.

INTRODUCTION

Johannes van der Walt passed away after a short illness on 13 November 2011. He will be remembered as a person very much interested in the biodiversity of yeasts, a passion which is apparent from the many yeast strains representing novel taxa that he isolated from various, mainly South African, sources.

The first yeast species that was isolated in South Africa was from an infected human nail and was described as Hanseniaspora guilliermondii by Adrianus Pijper (Pijper 1928), a pathologist practicing in Pretoria. The type strain of this species was deposited by Pijper in the yeast collection of the Centraalbureau voor Schimmelcultures (CBS), at that time located in Delft. The yeast collection had been transferred from Baarn to Delft after the appointment of Albert Jan Kluyver as Professor of Microbiology of the Technical University in Delft in 1921 (Samson ), and came back together with the CBS filamentous fungal collection in Utrecht in 2000.

As a result of Pijper’s mediation, Johannes van der Walt started to study for his PhD in Delft under the guidance of Kluyver in 1949, obtaining his degree in 1952 for a thesis entitled “On the yeast Candida pulcherrima and its pigment pulcherrimine” (van der Walt 1952). It was also in Delft that van der Walt was instructed in the use of specific enrichment techniques for the isolation of soil-borne microorganisms. After his return to South Africa in 1952, van der Walt started to search for novel yeast species. Applying a wide range of enrichment methods, van der Walt and his collaborators spent almost 50 years hunting intermittently for new taxa associated not only with natural sources such as uncultivated grassland soils, arboricolous beetle infestations and other similar niches, but also manufactured products such as wine and beer. This broad-based survey led to the discovery of many novel sexual and asexual ascomycetous taxa and some of heterobasidiomycetous affinity. Some of these species are still only known from South African isolates.

Although originally trained in chemistry, van der Walt developed a great interest in the systematics, ecology, and genetics of yeasts. His interest in yeast systematics was a consequence having the CBS yeast collection close to his work-place in Delft, facilitating his study of these organisms. From that time, van der Walt maintained strong connections with the CBS, consulting their yeast taxonomists on taxonomic problems, and by depositing 492 strains in the collection. These strains formed the basis for 20 new genera and 109 new species. Because of his broad knowledge of enrichment techniques, but also of yeast systematics, van der Walt was invited to contribute several chapters to the second and third editions of The Yeasts: a taxonomic study (Lodder 1970, Kreger-van Rij 1984).

Van der Walt’s broad knowledge of yeasts and his discovery of previously unrecognized genera and species was much respected by other yeast taxonomists, who named four genera and four species in his honour: Vanderwaltia (Novak & Zsolt 1961; now included in Hanseniaspora), Waltomyces (Yamada & Nakase 1985; now included in Lipomyces), Waltiozyma (Muller & Kock 1986; now included in Wickerhamomyces), Vanderwaltozyma by Kurtzman (2003), Torulopsis vanderwaltii (Vidal-Leira 1966; reclassified by Yarrow & Meyer 1978, as Candida vanderwaltii), Kluyveromyces waltii (Kodama 1974; reclassified by Kurtzman 2003, as Lachancea waltii), Myxozyma vanderwaltii (Spaaij ), and Bullera waltii (Sugita ; reclassified by Wang & Bai 2008, as Derxomyces waltii).

In the early years of taxonomy, a group of scientist that included Johannes van der Walt, Nico van Uden and Herman J. Phaff (Fig. 1), as well as Lynford J. Wickerham, made a huge contribution by using phenotypic characteristics of morphology and physiology for the description of novel genera and species. At that time, these features were considered as important for generic assignment and species distinction. One relevant practical contribution for species characterization was the introduction of the Diazonium Blue B (DBB) test by van der Walt & Hopsu-Havu (1976). In cases where the sexual cycle of a yeast was unknown, this DBB test could be used by yeast taxonomists to determine whether the yeast had an ascomycetous or basidiomycetous affinity. Basidiomycetous yeasts gave a dark red colour reaction when the DBB solution was applied, while this reaction was absent in ascomycetous yeasts.

Fig. 1.

Asci with ascospores of Kluyveromyces polysporus (Vanderwaltozyma polyspora) After Barnett . A. YM agar, 16 d. B. McClary acetate agar, 2 weeks. Bar = 5 μm.

Since the 1970s, following the trends set for bacterial taxonomy, molecular criteria such as mol% G+C and DNA-DNA hetero-duplex formations, and later gene sequencing, were introduced for the yeasts. Today, the introduction of novel species is predominantly based on molecular information obtained by sequencing one or several genes. This evolution in yeast taxonomy can be reconstructed from the five monographs on yeasts that have been published over the years (Lodder & Kreger-van Rij 1952, Lodder 1970, Kreger-van Rij 1984, Kurtzman & Fell 1998, Kurtzman ).

YEAST GENERA

Between 1964 and 1995, twenty novel yeast genera were introduced by van der Walt (Table 1). The first of these genera was Dekkera. Species of this genus are known as spoilage organisms of soft drinks and alcoholic beverages (Dequin , Dufour , Stratford & James 2003). Besides Dekkera, seven more genera were introduced by van der Walt as single author. Of the remaining genera, eight were published in collaboration with researchers at CBS and four with other authors.

Table 1. Genera introduced by van der Walt and co-authors.

Year	Genus	Author(s)	Present generic status1 (year of description of the genus)
1964	Dekkera	Van der Walt	Recognized
1970	Aessosporon	Van der Walt	Not recognized (ex-type culture mates with Sporidiobolus salmonicolor)
1971	Kluyveromyces	Van der Walt	Recognized
	Lodderomyces	Van der Walt	Recognized
	Cyniclomyces	Van der Walt & D.B. Scott	Recognized
	Wingea	Van der Walt	Not recognized (type species belongs to the genus Debaryomyces)
1972	Ambrosiozyma	Van der Walt	Recognized
1973	Wickerhamiella	Van der Walt	Recognized
	Entelexis	Van der Walt & Johannsen	Not recognized (status of the genus uncertain)
1976	Hyphopichia	Arx & van der Walt	Recognized
	Stephanoascus	M.T. Sm., Van der Walt & Johannsen	= Trichomonascus (1947)
1978	Pachytichospora	Van der Walt	= Kazachstania (1971)
	Debaryozyma	Van der Walt & Johannsen	Not recognized (the genus name Debaryomyces is conserved)
1980	Yarrowia	Van der Walt & Arx	Recognized
1981	Myxozyma	Van der Walt, Weijman & Arx	Recognized
	Arxiozyma	Van der Walt & Yarrow	= Kazachstania (1971)
1987	Zygozyma	Van der Walt & Arx	= Lipomyces (1952)
1990	Arxula	Van der Walt, M.T. Sm. & Y. Yamada	= Blastobotrys (1967)
1995	Babjevia	Van der Walt & M.T. Sm.	= Dipodascopsis (1978)
	Smithiozyma	Kock, Van der Walt & Y. Yamada	= Lipomyces (1952)

1 Present status in Kurtzman

As a consequence of the application of DNA sequence comparisons, eight of these genera were not accepted in the most recent edition of The Yeasts (Kurtzman ), but were reduced to synonymy (Table 1). The generic name Debaryozyma (van der Walt & Johannsen 1978) was not accepted because the proposal of Lodder & Kreger-van Rij (1978) to conserve the name Debaryomyces was approved (Greuter ) The monospecific genus Wingea is not now retained because the type species of this genus was phylogenetically shown to belong in Debaryomyces (Suzuki ). Further, since the ex-type culture Aessosporon was found to mate with strains of Sporidiobolus salmonicolor (Sampaio 2011, unpubl.), this generic name can be considered a synonym of the earlier Sporidiobolus. The status of the genus Entelexis is uncertain; Lachance commented on this in a discussion of Candida magnolia (previously Torulopsis magnoliae), since that species was indicated as the type species of Entelexis by van der Walt & Johannsen (1973).

YEAST SPECIES

Van der Walt was (co-)responsible for the introduction of 109 novel yeast species during the period 1956 to 1999 (Table 2). Of the taxa compiled in Table 2, 30 species were described by van der Walt alone, 15 in collaboration with co-authors at the CBS, and the remaining species with mycologists in other countries. Most of the type strains of these species are isolates from South African sources, and only 20 are from elsewhere. Thirty types were isolated from soil in different localities of South Africa; eight came from vegetable material; 35 from insect-related sources such as frass, tunnels or insect guts; ten are from processed food products such as beer, wine, and buttermilk; and three are from lichens.

Table 2. Species introduced by van der Walt and co-authors.

Year	Species name	Authors	Type strains of South African source	Type strains from other source	Present status of the type strain1
1956	Kluyveromyces africanus	Van der Walt	Soil		= Kazachstania africana
	Saccharomyces transvaalensis	Van der Walt	Soil		= Kazachstania transvaalensis
	Saccharomyces delphensis	Van der Walt & Tscheuschner	Dried figs		= Nakaseomyces delphensis
	Saccharomyces capensis	Van der Walt & Tscheuschner	Soil		= Saccharomyces cerevisiae
	Pichia vanriji (= P. vanrijiae)	Van der Walt & Tscheuschner	Soil		= Schwanniomyces vanrijiae var. Vanrijiae
	Saccharomyces pretoriensis	Van der Walt & Tscheuschner	Soil		= Torulaspora pretoriensis
	Kluyveromyces polysporus	Van der Walt	Soil		= Vanderwaltozyma polyspora
1957	Hanseniaspora vineae	Van der Walt & Tscheuschner	Soil		Recognized
	Saccharomyces telluris	Van der Walt	Soil		= Kazachstania telluris
	Hansenula beijerinckii	Van der Walt	Soil		= Lindnera saturnus
	Saccharomyces lodderae	Van der Walt & Tscheuschner	Soil		= Kazachstania lodderae
	Pichia terricola	Van der Walt	Soil		Recognized
	Pichia pijperi	Van der Walt & Tscheuschner	Buttermilk		= Wickerhamomyces pijperi
	Candida natalensis	Van der Walt & Tscheuschner	Soil		Recognized
1959	Endomycopsis wickerhamii	Van der Walt	Insect frass		= Barnettozyma wickerhamii
	Pichia robertsii (= P.robertsiae)	Van der Walt	Insect		= Debaryomyces robertsiae
	Endomyces reessii	Van der Walt		water-rotted Hibiscus cannabis, Indonesia	= Galactomyces reessii
1960	Torulopsis domercqii (=T. domerqiae)	Van der Walt & Kerken	Wine vat		= Wickerhamiella domerqiae
1961	Brettanomyces custersianus	Van der Walt	Brewery		Recognized
	Torulopsis vanzylii	Van der Walt & Kerken	Equipment of wine making		= C. norvegica
	Candida ingens	Van der Walt & Kerken	Wine cellar		= Saprochaete ingens
	Torulopsis cantarellii	Van der Walt & Kerken	Industrial grape must		= Trigonopsis cantarellii
	Torulopsis capsuligena	Van der Walt & Kerken	Wine cellar		= Filobasidium capsuligenum
1962	Schwanniomyces persoonii	Van der Walt	Soil		= S. occidentalis var. persoonii
1963	Saccharomyces vanudenii	Van der Walt & E.E. Nel	Soil		= Kluyveromyces lactis var. drosophilarum
	Fabospora phaffii	Van der Walt	Winery equipment		= Tetrapisispora phaffii
1964	Dekkera bruxellensis	Van der Walt		From Belgian stout, Belgium	Recognized
	Dekkera intermedia	Van der Walt		Tea-beer	= Dekkera bruxellensis
1965	Saccharomyces vafer	Van der Walt		Unknown	= Torulspora delbrueckii
	Saccharomyces inconspicuus	Van der Walt		Grapes, France	= Torulspora delbrueckii
	Saccharomyces inusitatus	Van der Walt		Beer	Possible hybrid between S. pastorianus and S. bayanus1
= Saccharomyces bayanus2
1966	Kluyveromyces cicerisporus	Van der Walt, E.E. Nel & Kerken		Unknown	= K. marxianus
	Kluyveromyces wikenii	Van der Walt, E.E. Nel & Kerken	Bantu beer		= K. marxianus
	Pichia acaciae	Van der Walt	Insect frass		= Millerozyma acaciae
1968	Candida edax	Van der Walt	Insect tunnels		= Sugiyamaella smithiae
	Torulopsis humilis	E.E. Nel & Van der Walt	Bantu beer		= C. humilis
1970	Saccharomyces amurcae	Van der Walt		“Alpechin”, Malaga, Spain	= Lachancea fermentati
	Saccharomyces saitoanus	Van der Walt		Sour milk, Japan	= Torulspora delbrueckii
	Hansenula philodendri	Van der Walt & D.B. Scott	Insect frass		= Ogataea philodendri
	Hansenula sydowiorum	D.B. Scott & Van der Walt	Insect frass		= Wickerhamomyces sydowiorum
	Syringospora stellatoidea	Van der Walt		Sputum	= C. albicans
	Syringospora claussenii	Van der Walt		Unknown	= C. albicans
	Aessosporon salmonicolor	Van der Walt	Carious dentine of man		Synonym of Sporidiobolus salmonicolor
	Bullera dendrophila	Van der Walt & D.B. Scott	Insect frass		Recognized
	Sterigmatomyces polyborus	D.B. Scott & Van der Walt	Insect tunnels		= Fellomyces polyborus
	Trichosporon melibiosaceum	D.B. Scott & Van der Walt	Insect frass		= C. fennica
1971	Pichia ambrosiae	Van der Walt & D.B. Scott	Insect tunnels		= Ambrosiozyma ambroasiae
	Pichia cicatricosa	D.B. Scott & Van der Walt	Insect tunnels		= Ambrosiozyma cicatricosa
	Saccharomycopsis synnaedendra	D.B. Scott & Van der Walt	Insect tunnels		Recognized
	Hansenula dryadoides	D.B. Scott & Van der Walt	Insect tunnels		= Starmera dryadoides
	Torulopsis dendrica	Van der Walt, Klift & D.B. Scott	Insect frass		= C. dendrica
	Candida silvanorum	Van der Walt, Klift & D.B. Scott	Insect frass		Recognized
	Candida dendronema	Van der Walt, Klift & D.B. Scott	Insect frass		Recognized
	Candida entomophila	D.B. Scott, Van der Walt & Klift	Insect tunnels		Recognized
	Torulopsis insectalens	D.B. Scott, Van der Walt & Klift	Insect tunnels		= C. insectalens
	Torulopsis nemodendra	Van der Walt, Klift & D.B. Scott	Insect tunnels		= C. nemodendra
	Torulopsis silvatica	Van der Walt, Klift & D.B. Scott	Insect tunnels		= C. silvatica
	Candida hylophila	Van der Walt, Klift & D.B. Scott	Insect tunnels		= Rhodotorula hylophila
	Torulopsis philyla	Van der Walt, Klift & D.B. Scott	Insect tunnels		= Rhodotorula philyla
1972	Ambrosiozyma philentoma	Van der Walt, D.B. Scott & Klift	Insect tunnels		Recognized
	Pichia melissophila	Van der Walt & Klift	Gut honey bee		= Priceomyces melissophilus
	Candida nitrativorans	Van der Walt, D.B. Scott & Klift	Insect tunnels		= Wickerhamomyces sydowiorum
	Candida entomaea	Van der Walt, D.B. Scott & Klift	Insect tunnels		= Yamadazyma mexicana
	Candida insectamans	D.B. Scott, Van der Walt & Klift	Insect frass		Recognized
	Candida insectorum	D.B. Scott, Van der Walt & Klift	Insect frass		Recognized
	Candida silvicultrix	Van der Walt, D.B. Scott & Klift	Insect frass		Recognized
	Candida amylolenta	Van der Walt, D.B. Scott & Klift	Insect frass		= Cryptococcus amylolentus
1973	Wickerhamiella domercqiae	Van der Walt	Wine vat		Recognized
	Candida homilentoma	Van der Walt & Nakase	Insect frass		Recognized
	Candida naeodendra	Van der Walt, Johannsen & Nakase	Insect frass		Recognized
	Entelexis magnoliae	Van der Walt & Johannsen		Flower	= C. magnoliae
	Aessosporon dendrophilum	Van der Walt	Frass of larvae in galleries of Dichrostachys cinerea		= Bullera dendrophila
1975	Hansenula lynferdii	Van der Walt & Johannsen	Soil		= Wickerhamomyces lynferdii
	Pichia philogaea	Van der Walt & Johannsen	Soil		= Yamadazyma philogaea
	Trichosporon terrestre	Van der Walt & Johannsen	Soil		= Blastobotrys terrestris
1976	Stephanoascus ciferrii	M.T. Sm., Van der Walt & Johannsen	Mating type a from soil		= Trichomonascus ciferrii
1978	Pachytichospora transvaalensis	Van der Walt	Soil		= Kazachstania transvaalensis
	Torulopsis azyma	Van der Walt, Johannsen & Yarrow	Lichen		= C. azyma
	Torulopsis geochares	Van der Walt, Johannsen & Yarrow	Soil		= C. geochares
	Candida fermenticarens	Van der Walt	Lichen		Recognized
1980	Debaryozyma yamadae	Van der Walt & Johannsen	Soil		= Schwanniomyces yamadae
1982	Hansenula euphorbiaphila	Van der Walt	Flower		= Cyberlindnera euphorbiiphila
	Pichia meyerae	Van der Walt	Flower		= Cyberlindnera meyerae
	Pichia kodamae	Van der Walt & Yarrow	Insect infestations		= Ogataea kodamae
1983	Pichia euphorbiae	Van der Walt & Opperman	Flower		= Cyberlindnera euphorbiae
1986	Kluyveromyces yarrowii	Van der Walt, Johannsen, Opperman & Halland		Stable mutant of crossing auxothrophic subcultures of CBS 2684 and CBS 6070, both isolated from tanning liquors of bark tree, France	= Vanderwaltozyma yarrowii
	Sporobolomyces kluyveri-nielii	Van der Walt	Leaf		Recognized
1987	Zygozyma oligophaga	Van der Walt & Arx	Insect frass		= Lipomyces oligophaga
	Candida lyxosophila	Van der Walt, N.P. Ferreira & Steyn	Soil		Recognized
	Myxozyma geophila	Van der Walt, Y. Yamada & Nakase	Soil		Recognized
	Myxozyma lipomycoides	Van der Walt, Y. Yamada & Nakase	Lichen		Recognized
	Sterigmatomyces wingfieldii	Van der Walt, Y. Yamada & N.P. Ferreira	Insect frass		= Cryptococcus amylolentus
1988	Sporobolomyces phyllomatis	Van der Walt & Y. Yamada	Leaf		Recognized
1989	Debaryomyces udenii	Van der Walt, M.T. Sm. & Y. Yamada		Soil, Ontario, Canada	Recognized
	Zygozyma arxii	Van der Walt, M.T. Sm. & Y. Yamada	Soil		= Lipomyces arxii
	Lipomyces japonicus	Van der Walt, M.T. Sm., Y. Yamada & Nakase		Garden soil, Japan	Recognized
	Zygozyma suomiensis	M.T. Sm., Van der Walt & Y. Yamada		Skin lesion of a cow, Finland	= Lipomyces suomiensis
	Myxozyma kluyveri	Van der Walt, Spencer-Martins & Y. Yamada	Soil		Recognized
	Sporobolomyces phylladus	Van der Walt & Y. Yamada	Leaf		= Bensingtonia phyllada
1990	Zygozyma smithiae	Van der Walt, Wingfield & Y. Yamada	Insect frass		= Lipomyces smithiae
	Myxozyma udenii	Spaaij, Weber, Oberwinkler & van der Walt		Soil around Magnifera indica, Florida, USA	Recognized
1992	Kluyveromyces picaeae	Weber, Spaaij & Van der Walt		Rhizosphere of Picea abies, Germany	= Kazachstania picaeae
1997	Lipomyces spencer-martinsiae	(Van der Walt & M.T. Sm.) van der Walt & M.T. Sm.		Soil, Nigeria	Recognized
1998	Myxozyma neglecta	Spaaij, Van der Walt & Weber-Spaaij	Cactus		Recognized
1999	Lipomyces doorenjongii	Van der Walt & M.T. Sm.	Soil		Recognized
	Lipomyces kockii	M.T. Sm. & Van der Walt	Soil		Recognized
	Lipomyces mesembrius	Van der Walt & M.T. Sm.	Soil		Recognized
	Lipomyces yamadae	Van der Walt & M.T. Sm.	Soil		Recognized
	Lipomyces yarrowii	M.T. Sm. & Van der Walt		Soil, Mauritius	Recognized

1 Present status in Kurtzman

One of the highlights of his career was the isolation of a strain that produced asci with more ascospores than the normal 1–4 ascospores which he described as Kluyveromyces multisporus (now Vanderwaltozyma polyspora; Fig. 2). One of his new species, Saccharomyces inusitatus, is now considered to have a hybrid genome on the basis of DNA/DNA reassociation experiments by A. Vaughan and A. Martini (Kurtzman ) with high levels of similarity to both S. bayanus (94 %) and S. pastorianus (91 %).

Fig. 2.

Three famous yeast taxonomists (left to right): Herman J. Phaff, Nico van Uden, and Johannes P. van der Walt. Photograph taken in 1987 at the international symposium “The expanding realm of yeast-like fungi”, Amersfoort, The Netherlands,

Van der Walt introduced 16 new combinations of species of which the basionyms were described previously by other yeast taxonomists. As these species are not seen as species first introduced by van der Walt we have not included them in Table 2. These species names, introduced by van der Walt on basis of basionyms of other yeast taxonomist and presently recognized, are listed below:

Ambrosiozyma monospora (Saito) Van der Walt 1972

Ambrosiozyma platypodis (J.M. Baker & Kreger) Van der Walt 1972

Cyniclomyces guttulatus (C.P. Robin) Van der Walt & D.B. Scott 1971

Hyphopichia burtonii (Boidin et al.) Arx & Van der Walt 1976

Kluyveromyces aestuarii (Fell) Van der Walt 1971

Kluyveromyces dobzhanskii (Shehataet al.) Van der Walt 1971

Kluyveromyces lactis (Dombrowski) Van der Walt 1986

Kluyveromyces marxianus (E.C. Hansen) Van der Walt 1971

Kluyveromyces wickerhamii (Phaff et al.) Van der Walt 1971

Lodderomyces elongisporus (Recca & Mrak) Van der Walt 1971

Myxozyma melibiosi (Shifrine & Phaff) Van der Walt et al. 1981

Myxozyma mucilagina (Phaff et al.) Van der Walt et. al. 1981

Saccharomycopsis vini (Kreger-van Rij) Van der Walt & D.B. Scott 1971

Torulaspora globosa (Klöcker) Van der Walt & Johannsen 1975

Torulaspora microellipsodes (Osterwalder) Van der Walt & E. Johannsen 1975

Yarrowia lipolytica (Wickerham et al.) Van der Walt & Arx 1980

CONCLUSIONS

Most of the species described early in his career by van der Walt were based on phenotypic features, and, as with genera, molecular data have led to the revision of the status of species described in the “pre-molecular era”. This is evident by comparing the initial status of the species with that in the present classification. From Table 2, it can be seen that 20 species were placed in synonymy with existing taxa, while 54 species were reassigned to different genera and are still recognized as well defined species. However, even after the addition of DNA sequence data, 34 species have retained their original status and stand as tribute to a great yeast taxonomist.

Even after his official retirement, van der Walt did not lose his passion for isolating interesting yeasts. For example, in 2010, over 20 years later, in collaboration with Teresa Coutinho, mating types of the presumed asexual species Candida deformans were isolated from lichens and soil (Groenewald & Smith, unpubl.). The last manuscript that he was actively involved with, resolving species within the Geotrichum/Galactomyces group (Groenewald ), was possible because South African strains he isolated in 2009 had been sent to CBS.

The yeast community is indebted to van der Walt for his contribution to the yeast biodiversity and taxonomy over 63 years. It is also likely that further novel taxa remain to be discovered among the strains that he has deposited over the years, supporting the quotation of Pliny (23–79 AD) “Ex Africa semper aliquid novi”, a quotation that Johannes van der Walt was fond of citing.

On a personal note, one of us, M. T. S., who collaborated with van der Walt for many years adds: “Those who may have had the privilege to meet Johannes van der Walt or to collaborate with him, as I have, will definitely remember him not only from his taxonomic work, but will also remember him as an amiable person full with stories to tell while enjoying a fine dinner with a good glass of wine.”