Selection and breeding for insect and disease resistance

Pest and disease resistance has been an essential part of crop breeding for many years, but has only had marginal impact in tree breeding to date. Crop varieties are domesticated and their continued cultivation depends on continuous breeding programmes for insect, disease and virus resistance, since large-scale monocultures are generally more susceptible to variable pathogens. Forest trees are mainly wild, undomesticated, outbred organisms and their natural populations retain a wide genetic diversity that helps them resist insect pests and pathogens. In addition, the genetic control of insect pest and disease resistance is sophisticated and probably more complex than for annual crops. Moreover, conventional tree selection and breeding for insect and disease resistance requires complex and lengthy laboratory and field tests, especially since resistance patterns may change from young to adult trees.

Over the past 20 years, tree breeding programmes have been reduced worldwide and now focus on a limited number of species and traits. However, since the risk of introducing new pests is likely to increase in the future, insect and disease resistant breeding programmes may be particularly important for several large-scale or valuable commercial plantations.

Pest resistance breeding may be a technical option in large-scale or valuable commercial plantations if there:

  • are few silvicultural options to mitigate losses to insect pests and diseases;
  • are no alternative species;
  • is an increasing risk of introductions of exotic pests.
In order to determine the global status of research and applications regarding breeding for resistance in the forest sector, in 2006 the FAO Forestry Department, in collaboration with Alvin Yanchuk of the Tree Improvement Branch, British Columbia Ministry of Forests, Canada and Nicholas Wheeler of the Molecular Tree Breeding Services, US, conducted an informal yet comprehensive review of the topic. This 2006 review has been updated based primarily on information gathered from the recent 4th International Workshop on the Genetics of Host-Parasite Interactions in Forestry: Disease and Insect Resistance in Forest Trees, held in Eugene, Oregon, July 31 to August 5, 2011. For more details of some of the more recent research activities in pest and disease resistant breeding, see the proceedings of the meeting. 

It is hoped that the proceedings and these web resources will give practitioners and reporting agencies a snapshot of the level of activity in pest resistant breeding around the world, and help to focus it where future efforts would be best applied.

last updated:  Thursday, January 24, 2013