Analysis

A total of 260 activities on breeding for insect and disease resistance in forest trees were recorded in this review. Note that these summary records were not intended to capture all publications of resistance on a particular species (e.g. the P. taeda fusiform resistance programme has hundreds of scientific publications in the literature), but to simply reflect on the activities relative to others around the world.

By forest tree species

Thirty-six tree genera were represented. Pines (Pinus spp.) and poplars (Populus spp.) were the two most commonly investigated genera representing 30% and 26% respectively of all activities recorded. Eucalypts were the focus of 5% of the activities; spruce (Picea spp.) and birch (Betula spp.) almost 4% each; larch (Larix spp.) and Douglas fir (Pseudotsuga spp.) almost 3% each; and chestnut (Castanea spp.), willows (Salix spp.) and elms (Ulmus spp.) at almost 2% each of all activities.

The most studied tree species included Pinus radiata (16 records), P. taeda (9), and P. monticola and P. ponderosa var ponderosa (six records each). Picea abies and Pinus contorta were the focus of five of the activities each, and Betula pendula, Cryptomeria japonica, Eucalyptus globulus, Hevea braesilensis, Pinus lambertiana and Populus deltoides were each the focus of four of the activities.

By pest type and species

Over 54% of all activities reported in this review investigated tree resistance to disease species, over 36% targeted forest insect pests and over 6% investigated both pest types. Resistance to mammals was the focus of six of the activities (over 2%) and one activity dealt with nematodes.

The most commonly investigated insect pest species included Chrysomela scripta (5 activities), Pissodes strobi (4) and Thecodiplosis japonensis (4). For diseases of forest trees, the most commonly investigated species included Cronartium ribicola (18 activities), Cronartium quercuum (7), Diplodia pinea (4), Heterobasidion annosum (4), Melampsora larici-populina (4) and Ophiostoma ulmi (4).

By country

The majority of research activities are published in developed countries, such as the United States (over 38% of all activities), Canada (over 6%), Japan and New Zealand (almost 6% each), and France and Australia (5% each), although some emerging developing countries, such as China (over 8%), India (3%) and Brazil (over 1%) are active or at least publish and disseminate their results.

By approach

The majority of activities, over 68%, focused on traditional plant breeding methods (Approach 1). Genetic engineering (Approach 3) was the focus of 38 (almost 15%) of the activities while molecular biology approaches (Approach 2) were investigated in 33 of the activities (almost 13%). Twelve of the activities used a combination of the three approaches.

By status

The majority of research activities, 163 representing almost 63% of all activities, have provided evidence of genetic variation in resistance in seedling or clonal screens (Status 4). In 57 of the activities, resistance has been detected in genetic/provenance trials (Status 3). Twenty-four of the recorded activities represent breeding programmes with deployed resistant material (Status 1) while 16 of the activities represent breeding for resistance programmes but with no deployed material (Status 2).