Friday, 21 August 2015

Putting the culture back into horticulture

Breeding for biodiversity and sustainability with the help of the public.
The case of Oxalis tuberosa.
Part of the coursework for my RHS Special Option Certificate in Fruit and Vegetable Cultivation took the form of a dissertation, so I made use of the opportunity to explore a topic that I had at heart.

For the last year I have been supporting the launch of a collaborative breeding project for oca (Oxalis tuberosa) in the UK: the Guild of Oca Breeders. Oca is an Andean tuber crop which starts tuberising when days get shorter at the end of the summer. However, in temperate climates, the underground growth of the tuber is checked by frost, which kills the leaves above the ground. The same happened to the potato when it was first introduced in Europe, before day-neutral varieties were bred. The Guild aims to do the same with oca, which is a delicious tuber and an alternative to potato. Because breeding is a resource-intensive process, and since there is little or no commercial interest in sponsoring it, the project wants to mobilise the help of voluteers.

As I explored the various aspects of the project, I realised that a great deal of interesting topics had to be touched upon:
  • the relationship between culture and agriculture: people plants and the land; 
  • the breeding requirements for small and sustainable growers: resilient, locally adapted varieties, rather than uniform crops suitable for shipping around the world (which are favoured by "conventional", industrial agriculture)
  • the intricacies and costs related to plant breeding rights and their impact on access to seeds;  
  • issues of financial viability for small breeders and the opportunities from the "citizen science" movement.

With limited time on top of a full time job and plenty of other coursework, I could only scratch the surface, but I think my dissertation works as a very high level introduction to the topics above, referencing some rather interesting articles - so I decided to publish it here.

The table of contents goes as follows:

Putting the culture back into horticulture

  • Edible crops for the future
  • Sustainability, knowledge and culture
  • Biodiversity for resilience
Plant breeding and participatory models
  • Issues with current breeding methods and legislation
  • Breeding for low input and marginal lands
  • Participatory Plant Breeding
  • Citizen science, open source, open data
Oca breeding and the Guild of Oca Breeders
  • Oca a crop for the future
  • Small scale oca breeding
  • The Guild of Oca Breeders

Tuesday, 18 August 2015

PD&D: pests, diseases and disorders

As part of my coursework for the certificate, I had to write a Pest and Disease project. I researched 15 of the most common pests (vertebrates and invertebrates that feed, inhabit or otherwise live off plants, damaging or killing them) and diseases (caused by microorganisms such as fungi, viruses and bacteria), ones that I had the opportunity to see in person at Wisley.

We were not required to study disorders, which usually go together with the other two categories in the acronym "PD&D"; disorders are physiological conditions that cause the plant to behave abnormally, for whatever reason except pest and diseases (i.e. nutrient deficiencies, drought, heat, physical damage etc.) - they are very difficult to identify, as this excellent guide from Michigan State University explains.

One such disorders I encountered at Wisley was on 'Conference' pears. In some years more than others (maybe due to some nutrient deficiency and possibly facilitated by dry weather), some pears develop corky lesions on their skin, which may on occasion be mistaken for fungal disease scab (Venturia pirina) but have been identified as a likely disorder. 'Conference' pears are particularly prone to them: I had it on my tree at home and receveid a good few questions from visitors that spotted it in the Fruit Garden. Dealing with it means simply removing the worst affected fruitlets so they do not take up the plant's energy; most fruit grows out of it to be happy pears anyway.

Disorder, unspecified (badly affected fruitlets, left; mildly affected, right)
Pear scab (Venturia pirina) damage
But back to my project, on pests and diseaseses... knowledge is for sharing, so here it goes:

The table of contents:


Apple (Malus domestica) and pear (Pyrus communis)
Brown rot of apple and pears (Monilinia fructigena, M. laxa)
Apple and pear canker (Neonectria galligena
Apple powdery mildew (Podosphaera leucotricha)
Rosy apple aphid (Dysaphis plantaginea)
Codling moth (Cydia pomonella)
Apple and pear scab (Venturia inaequalis, V. pirina)

Blackcurrant (Ribes nigrum)
Big bud mite (Cecidophyopsis ribis)

Gooseberries (Ribes uva-crispa)
Gooseberry sawfly (Nematus ribesii)

Grapes (Vitis spp)
Grey mould (Botrytis cinerea)

Raspberry (Rubus idaeus)
Raspberry beetle (Byturus tomentosus)
Cane blight (Leptosphaeria coniothyrium)


Cabbage (Brassica oleracea)
Cabbage root fly (Delia radicum)
Mealy cabbage aphid (Brevicoryne brassicae)

Leek (Allium porrum)
Leek rust (Puccinia allii)

Pea (Pisum sativum)
Wood pigeons (Columba palumbus)