Knowledge of plant defence mechanisms provides a foundation for the development of novel biotechnology 

strategies to curb losses due to pests and pathogens. We are exploiting the knowledge gained from Eucalyptus

and pines to determine defence pathways and genes to confer resistance against the scores of pests and pathogens that

currently threaten productivity in these species.

 

Invasive pests have become major problems in plantation forestry and as global trade increases, it is apparent that curbing

the tide of new introductions is becoming more challenging. One invasive pest, Leptocybe invasa induces gall formation on

Eucalyptus trees. We are curious about the early mechanisms leading to gall formation in susceptible trees. To this end, we

are looking at transcriptional reprogramming induced by egg deposition. This will allow insight into host defences that are

overcome by the pathogen.

 

Pine species are among the world’s most widely grown tree species as both native and plantation forests. More

recently, genomic efforts for pine species have increased primarily due to the decrease in sequencing costs. We have invested in the sequencing of pine

transcriptomes for major species grown in South Africa. This provides the resources to determine the mechanisms underlying resistance and susceptibility

to various pine pests and pathogens. A major pathogen is Fusarium circinatum which causes pitch canker disease in the field. This pathogen produces a type of

wilt in young seedlings under nursery conditions, severely limiting the production of the susceptible species. Our research has focused on defence mechanisms

against the pathogen in young seedlings.

 

Two major avenues exist to produce superior genotypes with enhanced resistance to the pathogen. One is marker aided selection and the other, genetic

engineering. We have concentrated efforts in both avenues and have recently identified markers for tolerance against Leptocybe invasa. We are exploring

the CRISPR-Cas9 system for genome editing in Eucalyptus to test candidate genes related to resistance engineering. We are thus well-positioned to achieve

the goal of improving tree resistance against major pests and pathogens in future.