Mechanisms of cultivar- and race-based disease resistance in avocado (AV09024)

What was it all about?

Phytophthora root rot caused by Phytophthora cinnamomi is a serious problem in avocado trees resulting in low productivity and small, poor quality fruit. If left untreated, Phytophthora root rot will eventually kill affected trees. Rootstocks with high levels of resistance to Phytophthora root rot are not available in avocado, yet differences in tolerance to the disease have been observed among commonly used rootstock varieties.

This project set out to understand the mechanisms underlying tolerance and resistance to this pathogen, and to identify less susceptible rootstock varieties. Researchers tested a number of physiological characteristics of trees to see if they provided protection.

Glasshouse root growth studies found no relationship between inherent root growth and susceptibility to the disease among nine seedling varieties. Researchers also found no correlation between susceptibility and stored starch, tree health, yield or tree growth parameters in field trials at two sites. Root regenerative ability was also not a factor.

Further research will be needed to identify differences that improve resistance.