Background

This project aims to increase the understanding of olive varietal performance in Australia.  Growers will have greater confidence in choosing olive varieties to suit their particular requirements.  The project is jointly funded by the olive industry, RIRDC and PIRSA.

Objectives

To deliver informed and skilled olive orchard management through provision of:

1. A nationally coordinated technical and educational support network.
2. Comparative physiological information on the performance of all known olive varieties in Australia.
3. Survival, growth and management information from a range of olive varieties across a range of climatic/edaphic conditions in Australia.

Key Achievements

The following are some highlights from the project.

Yields:  The best performing varieties in terms of total fruit yield at Roseworthy were (in descending order): Picual, UC13A6, Barnea, Hojiblanca, Arbequina, Koroneiki, Group VII and Manzanilla de Sevilla.

Oil Content in Dry Flesh:  The varieties with highest percentage oil content in dry flesh at Roseworthy were (in descending order): Buchine, Group V, Gros Reddeneau, Manaiki, Group IV, Arbequina, FS17, Atro Rubens, Barnea, Regalise de Languedoc, Volos, Souri, Mission (WA), Frantoio, Coratina, Columella, Nevadillo Blanco, 177, Ascolano, Kalamata, Gordal Sevillana, Pigale, Verdale Aglandau, Verdale (Blackwood), Oblitza, Group I and Picual.  However, not all of these varieties yielded well at Roseworthy so would not produce a large total amount of oil.

Water in whole fruit:  Some of the varieties commonly used for oil in Australia have relatively high fruit moisture content such as: Verdale (SA), Manzanilla de Sevilla, Picual, Hojiblanca, FS17, Pendolino, Barnea, Arbequina and Leccino.  They may require careful irrigation management before harvest to avoid high fruit moisture content and may not be suitable for areas that commonly experience rainfall around harvest time.

Conversely, those varieties with naturally low fruit moisture content may be more suited for oil production in areas that commonly experience rainfall around harvest time.  Varieties with low inherent fruit moisture content are: 177, Manaiki, Group II, Amelon, Large Pickling, Nevadillo Blanco, Group IV, Kalamata, Volos, Dr Fiasci, Atroviolacea Brun Ribier, Pigale, Mission (Californian), Blanquette - Early, Gros Reddeneau, Verdale (Blackwood), Coratina, Black Italian, Mission (WA), Frantoio (including Bouteillon, Pueblana, Corregiola, Leccure and Paragon), Group V, Buchine and Koroneiki.

Oil Chemistry:  A number of varieties consistently recorded levels of linolenic acid higher than the IOOC allowable limit of 1%, both at Roseworthy and around Australia.  They were:  Verdale (SA), Group II (includes Wagga Verdale), Gordal Sevillana (includes Sevillano), Group VI, Rouget, Areccuzo, Group I, Benito, 177, FS17, Hardy's Mammoth, Oblitza and Katsourela.  Growers producing olive oil from these varieties should be aware of their susceptibility in producing levels of linolenic acid above the IOOC accepted limit, however there may be an opportunity to blend oils to reduce overall linolenic acid level.

A high level of oleic acid is desirable in olive oil.  Those varieties with high oleic acid levels in this study were:  Group IV, Black Italian (Blackwood), Katsouroniki, Group VI, Group V, Koroneiki, Buchine, Kalamata, Mission (Californian), Leccino, Regalise de Languedoc, 177, Picual, Coratina and Hojiblanca.

Similarly, a high ratio of monounsaturated:polyunsaturated fatty acides (MUFA:PUFA ratio) in the oil should confer stability to the oil.  Those varieties at Roseworthy, in 2004, with a ratio greater than Picual, noted for having highly stable oil in descending order are: Group V, Black Italian (Blackwood), Group IV, Leccino, Koroneiki, Group VI and Manzanilla de Sevilla.  Consequently their oil should be highly stable.

Variety recommendations: Koroneiki appears to be the outstanding performer for olive oil production in Australia, based on the criteria examined in this study.  It was a consistently high yielding variety at Roseworthy and it has high oleic acid levels and a high MUFA:PUFA ratio, conferring stability, and is less inclined than the seven other varieties evaluated in detail, to reduced oleic acid levels and increased linoleic levels with increasing temperatures during oil accumulation.  It also has inherently low fruit moisture content, facilitating oil extraction, making it more suitable than some other varieties for warmer, more humid environments.  Its oil has performed well in Australian extra virgin olive oil competitions (Gawel R, pers comm.).  Its fruit was taken by birds for some years at Roseworthy, indicating potential vulnerability to bird predation and risk of spread as a feral plant.  Also, being small fruited it may be difficult to harvest.

Picual also performed well in most of these criteria except for the tendency of its fruit to absorb moisture, making it less suitable for areas of high rainfall during harvest.  In drier areas with astute irrigation management it should perform well.

Kalamata, Coratina and Californian Mission did well in most of the criteria although their oil stability was not as high as other varieties in terms of the MUFA:PUFA ratio.  With Kalamata and Coratina there is concern regarding productivity in terms of fruit yield at Roseworthy.  They are still young trees but were certainly not yielding well in comparison to other varieties and may already be tending toward alternate bearing.  However, they were only evaluated in a few of the agro-climatic regions and more information is needed.

Buchine, and accessions in Group IV And Group V are not widely planted in Australia but look interesting as they have high oil content (particularly Buchine), oleic levels and MUFA:PUFA ratio (except Buchine), as well as low water percent.  However their yield performance at Roseworthy was poor and they need to be evaluated in other environments.

Hojiblanca and Leccino were starting to yield well at Roseworthy and had high oleic levels and Leccino had a high MUFA:PUFA ratio.  However their fruit water content was reasonably high and oil content only moderate.

Barnea and Arbequina are two widely planted varieties in Australia and both yielded well at Roseworthy with high oil content.  However fruit moisture content is high, particularly with Barnea, and similarly to Picual will need careful irrigation management close to harvest.  Their MUFA:PUFA ratios (and consequent stability) are lower than other varieties and Arbequina has a high palmitic acid value.

Frantoio yielded poorly at Roseworthy, but has high oil content and low fruit water content, no doubt contributing to its reputation as an easily processed variety.

In terms of yield, fruit weight and flesh:pit ratio, Jumbo Kalamata, UC13A6, Barouni, Volos, Azapa, Benito and Manzanilla de Sevilla were the best performing table fruit varieties studied.  However there are other characteristics important for table olives not evaluated in this study.

Project Leader: Susan Sweeney