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JAN TOERIEN
South African Avocado Pioneer
An Extract from His Memoirs
Jan graduated in 1965 and started his career in the South African office
of Chesterford Park Research based in Cambridge UK. In 1971 he joined
Ciba-Geigy and in 1973 he started his career with Westfalia in Tzaneen,
South Africa.
He was immediately confronted by Phytophthora cinnamomi, a huge problem,
both in the nursery and in the field. He wrote in his memoirs “The
California Avocado Yearbooks became the ‘avocado bible’ to me and I
studied it in depth.” In 1976 he undertook a study tour to Israel and
California where he was well received by a large number of researchers.
A breakthrough came when Prof. George Zentmyer showed him some
Phytophthora cultures. He observed a dramatic inhibition in one culture
treated with a Ciba-Geigy product.
Back home he shared this observation with Ciba-Geigy who formulated a
wettable powder based on the coded fungicide in Prof. Zentmyer’s
collection. This resulted in the registration and commercial application
of Ridomil. Jan states “the trees recovered fantastic” but soon Jan and
his team observed a progressive Phytophthora resistance to Ridomil.
This prompted Jan to look for a Phytophthora resistant rootstock and
thus was instrumental in laying the foundation for the current
successful rootstock selection program at Westfalia. Under his
leadership there were a large number of rootstocks showing potential and
Jan exchanged 10 of the most promising ones with Dr. Mike Coffey at UC
Riverside. Further, Jan initiated a selection program on Westfalia
Estate aimed at identifying so called escape trees (i.e. avocado trees
on unknown seedling rootstock growing remarkably healthy in orchards
with high Phytophthora pressure). Among the most successful rootstocks
to date coming from this program is the Dusa (Merensky 2), now grown
worldwide.
In the meantime he and the Westfalia team developed the phosphorous acid
tree injection treatment. This treatment was met with much skepticism,
but proved to be the long term commercial solution. Soon the Westfalia
avocado trees were saved from Phytophthora.
Jan writes in his memoirs “Now we had healthy trees and were confident
that we could produce good quality fruit. This however was not the case
and we looked at every possible cause, from mineral nutrition to cooling
rates, to air circulation through pallets and cold storage conditions.”
This work resulted in two postharvest treatment protocols for South
African avocado.
First, he looked into high carbon dioxide shock treatments prior to
shipping. This approach was followed because CA shipping containers were
not yet developed. This technique drastically reduced chilling injury
and reduced quality losses but was difficult to implement. All these
problems were however solved with the advent of CA containers.
Secondly, he proved that too fast cooling induced chilling injury and he
and his team developed a step-down temperature regime from picking to
marketing. This in itself resulted in a dramatic improvement in market
quality of Westfalia avocados in the European market.
Jan also contributed to the world avocado knowledge by frequently
sharing information with the worldwide community through publications of
articles in both the South African Avocado Growers’ Association Yearbook
and the California Avocado Society Yearbook. In 2007 he prepared two
articles reviewing the development of the phosphorous acid tree
injection technology and a tribute to its developer, Dr. Joe Darvas for
the California Avocado Society Yearbook.
Jan Toerien laid a sound technical foundation for super plant material,
for modern production procedures and for practical postharvest protocols
benefitting the international avocado industry. Jan made many friends
all over the world; he was instrumental in creating the first
International Avocado Congress in 1987 and served as the first President
of the International Avocado Society. He will be honored as the
cornerstone of the South African avocado industry and a motivator of the
quadrennial World Avocado Congress. He shared all his knowledge and
experience with his friends and colleagues in the global avocado
village.
Gawie Eksteen, Kleinmond, South Africa
10/19/2010
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