9 WHY DO WE NEED CONTINUED EFFORTS IN AVOCADO SCION AND ROOTSTOCK IMPROVEMENT

The California avocado industry is dominated by a single variety, ‘Hass’. Although this va-riety has some excellent attributes such as good eating quality, relatively high yields under favorable conditions and reliable postharvest attributes the variety is also has a number of problems. Some of these problems include small fruit size (especially as the tree ages); intolerance to extreme climactic conditions, alternate bearing and sensitivity to certain in-sect pests (greenhouse thrips, Persea mite and avocado thrips). The introduction of more reliably producing varieties should help to stabilize production swings. Consistently heavier yields per acre can lower production costs per pound. The biodiversity resulting from a multi-variety industry should slow the spread of diseases and pests like Persea mite, avo-cado thrips and others that may well appear in the future. Two new avocado cultivars, ‘Lamb Hass ’ and ‘Sir Prize ’ have been recently patented and released by the University of California. The ‘Lamb Hass ’ in particular shows promise as a new variety for the California industry. The tree has an upright growth habit, possibly conducive to high density plantings and/or intensive canopy management. It has also demonstrated some apparent tolerance to the Persea mite. The fruit is ‘Hass’-like in appearance and matures later in the seaso