The quest for sterile seed in black wattle

Introduction to our ‘Guest Blog’ below (by Marnie Light)

Shelagh and I thought that an article by Dr Sascha Beck-Pay would be an interesting addition to the blog. Sascha, one of my colleagues, worked on a project for several years with the aim of developing a sterile black wattle tree in order to reduce the seed load of this commercially important, yet invasive species, in South Africa. So, in one sense this research does fly in the face of seed scientists (we love to see seeds germinate!), but it does highlight some interesting research…

Guest Blog by Sascha Beck-Pay (Senior Research Scientist at the Institute for Commercial Forestry Research, South Africa)

In South Africa, black wattle (Acacia mearnsii) is a leading commercially grown forestry tree species. However, it is also considered to be an exotic invader of indigenous vegetation. This ‘alien invader’ status adds pressure on the forestry industry, making future afforestation to black wattle difficult, particularly for small-scale growers. Thus, the production of a sterile or seedless variety of black wattle was considered a favourable solution to help reduce the contribution of seed to the existing seedbank, thereby potentially removing the invasive status of black wattle whilst allowing the forestry industry to continue as a thriving contributor to the South African economy.

A project was conducted within the Acacia Breeding Programme at the Institute for Commercial Forestry Research (ICFR) in South Africa to try and produce a sterile or seedless tree using the following two approaches:

  • The production of a triploid variety; and
  • The use of gamma irradiation techniques to produce sterile trees.

With the first approach, tetraploids were successfully induced and controlled-crosses were made with diploids. Due to the fact that no triploids were produced from the controlled-crosses, reproductive biology studies were conducted to investigate possible barriers that could be preventing this. Fluorescent microscopy revealed that, in the cross between diploids and tetraploids, the pollen tubes were reaching the ovary and ovules indicating that fertilisation was possible and that the barrier preventing seed maturation was located within the ovary. Embryo rescue, using tissue culture techniques, was then attempted at varying stages of pod development post-fertilisation. Due to the small size of the pods, however, it was impossible to identify and isolate a clean embryo, devoid of maternal tissue, until 11 months post-fertilisation, at which stage embryo abortion would have occurred.

The second approach tested the use of gamma irradiation to induce sterility in seeds. Samples of seed were irradiated, the seedlings raised in a nursery, and then established in a field trial. It was apparent that reductions in flowering and seed production occurred at doses of 350, 400, 450 and 520 Gy. Although seed production was not completely eliminated, reductions of up to 50 % were recorded. Where seed was produced, the seed was determined to be viable, leading to the conclusion that, although seed production can be reduced, the viability of the seed is not affected and thus gamma irradiation does not affect the female reproductive structures of the plant. This suggested that reduced flowering and resultant lower seed production could be as a result of male sterility, although this still needs further investigation. At the doses tested, there was no detrimental effect on the growth of the trees, which makes this approach to reducing seed production quite promising.

The project was conducted over a period of 12 years from 2000 to 2012 and, although a number of advancements were achieved in trying to produce a sterile or seedless variety of black wattle, the project was closed due to funding constraints. For more information contact Sascha Beck-Pay, or for click here for further reading.

Black wattle inflorescences Diploid and tetraloid polyadsStigma with multiple polyads attached

In memory of Prof. Berjak (South Africa)

It is with much sadness that we recently learned of the death of Prof. Patricia Berjak on the 21st January 2015. Prof. Berjak was a world-renowned seed scientist, with a particular interest and expertise in recalcitrant seed biology. She served as the President of the International Society for Seed Science from 2008 until 2011, and has presented many interesting research papers around the world. Indeed, Prof. Berjak made a remarkable contribution to botanical research, especially concerning our understanding of seed physiology and technology. She will be missed.

Click here for an obituary on Prof. Patricia Berjak.

Small spores, but potentially big impact!

Introduction to our ‘Guest Blog’ below (by Shelagh McCartan)

During December, I was routinely assessing seeds that had failed to germinate during a germination test. Sometimes, ungerminated seeds can be overwhelmed by various moulds, particularly when incubated at warm temperatures for a few weeks.  On this occasion, I spotted an unusual-looking mould, which I passed onto Caroline Gorton for identification. She identified it as an Aspergillus mould – from which a person can develop health problems. It is, therefore, important to be aware of this, and take the necessary precautions. The bottom line is to ‘work smart and stay safe’!

Guest Blog by Caroline Gorton (Diagnostician in the Tree Health Advisory and Diagnostic Service, Forest Research, Britain)

Aspergillus is a ubiquitous mould found in air and soil.  Aspergillus, like other moulds, thrives in humid environments and spores can reach high levels in damp housing and compost.  Most people are immune to infection; however, people with damaged lungs, allergies or a compromised immune system may develop aspergillosis.  The type of disease can vary from an ‘allergy’ type response to life threatening invasive infections.

These images were taken of Aspergillus which had grown in a germination box containing seeds of European silver fir (Abies alba).  As Aspergillus is a common member of the microbial flora, it may well be present on seeds which are incubated and the moist conditions are perfect for its growth.  It is, therefore, worth being aware of when assessing seeds as the spores can cause significant health problems.  It is advisable to work in a well-ventilated environment or to wear a HEPA filter face mask if moulds are present.  Further information is available here.

Aspergillus 3 Aspergillus

Season’s Greeting from the Group Co-ordinators

It is really hard to believe that 2014 is almost at an end! Looking back over the year, we have ‘planted some small seeds’ that we hope will flourish into the future. We have made contact with some new members to the group and managed to get this blog started (although we did not publish as many posts as we would have liked to… it is a start). Even more exciting, is that we have also been in discussions around hosting a small conference next year, and plans to do so are underway – so look out for more information on that early in January 2015!!! We are really looking forward to it!

Wishing you all the very best over the Festive Season, and for the New Year ahead!

Shelagh and Marnie

Holly heavy with berries.Rose hips aca

Manufactured seed – Is this the future?

Introduction to our ‘Guest Blog’ below (by Shelagh McCartan)

During September, I was able to attend a very well-organised conference in Vitoria-Gasteiz, Spain (IUFRO Working Party 2.09.02 – Somatic Embryogenesis and Other Vegetative Propagation Technologies). For more information on the conference click here. I learned a great deal, particularly around the problems regarding ‘maturation of embryos’ and ‘conversion to plantlets’, and I believe that there is scope for input from seed scientists. I was particularly fascinated by the presentation by Jeff Hartle and his colleagues from Weyerhaeuser on ‘manufactured seeds’, and requested Jeff to send us some more information on this interesting topic.

Guest Blog by Jeff Hartle (MSeed Development Scientist, Weyerhaeuser Co.)

Modern agriculture often requires the planting of large numbers of genetically identical plants that have been selected to have advantageous properties. Production of new plants by sexual reproduction, which yields botanic seeds, is usually not feasible. Asexual propagation, via several pathways has been used for many years to produce large numbers of genetically identical individuals. In many species these are called varieties. One method to produce varieties is to use somatic embryogenesis. At Weyerhaeuser, we have developed machinery, protocols and logistics for the large-scale automated production of conifer somatic embryos. We have also developed a synthetic seed technology we call ‘manufactured seed’ that are made on an automated assembly line. This system allows large quantities of manufactured seed to be produced with minimal labor. As compared to most clonal techniques, the use of somatic embryos with manufactured seed allows steady-state manufacturing. As manufactured seed are created, they can be stored allowing a large quantity to be produced over time. When conditions are right for planting, the manufactured seed can be pulled from storage and planted en-masse. Manufactured seed also allows for centralized manufacturing with shipping to various facilities for planting. We have tested manufactured seed with several conifer species, but also found good performance with dissected corn, wheat and soybean embryos.  For further information, click here.

JH1-r JH3-r JH2-r

It’s all happening in Salt Lake City, USA!

In 2010, I was very privileged to attend the IUFRO World Congress in Seoul, Korea. It was my first opportunity to attend such an enormous conference, with over 2500 delegates from around 90 countries – and what a fantastic experience it was! This year, a few of my South African colleagues have travelled across the Atlantic Ocean to attend the IUFRO 2014 World Congress in Salt Lake City, USA, and I am sure it will be another outstanding event (you can follow the current updates on the Congress here)! We would love to get some feedback on the Congress to put on this blog, so if you, or a colleague, have been fortunate enough to attend the IUFRO World Congress this year, then we’d love to hear from you!

You may be wondering… what events are happening in the world of ‘seed science’ in the near future?

Well, we are very excited about the upcoming International Society for Seed Science (ISSS) Seed Longevity Workshop which will be held in Wernigerode, Germany, from 5-8 July 2015. This promises to be a very interesting workshop with a great selection of keynote speakers that have been confirmed. The topic of the conference is “Seeds for future generations – Determinants of longevity”. For more information, click here.

And… we are also in the process of planning a small conference for 2015… so, ‘watch this space’ for more information!

Conferences – too few and too far?

The ISSS conference in China is less than three weeks away! Are you registered? If not, when last did you attend a seed science conference? Which factors do you consider critical when signing up for a conference?

Please take our short poll above so that we can get some feedback from you on whether there is sufficient demand and interest for a seed science conference early to mid 2015.

Thanks for you participation!






Introducing the Working Group Deputy, Dr Marnie Light


Marnie at a Pinus patula pot trial set up to investigate a nursery pathogen.

Dr Marnie Light (Working group deputy coordinator)

Programme Manager / Scientist at the Institute for Commercial Forestry Research, South Africa

What do I do?

Manage a small team of researchers and technicians to conduct research related to silvicultural management of commercial pine or eucalyptus plantations in South Africa. This programme covers research on:

  • Pine and eucalypt regeneration
  • Eucalypt coppice management
  • Vegetation management
  • Integrated pest management

Communicate research findings and practical applications to our stakeholders and relevant private growers.

Publish relevant reports and peer-reviewed papers.

Assist and mentor students.

Through an honorary appointment at the University of KwaZulu-Natal, I conduct some research related to smoke-stimulated seed germination.

For more information, Marnie can be contacted at

…a discussion forum for seed scientists world-wide.