Variation in Sharwil avocado maturity during the harvest season and resistance to fruit fly infestation.

Authors: CHEN, NANCY - UNIVERSITY OF HAWAII; Wall, Marisa; ROBOERT, PAULL - UNIVERSITY OF HAWAII; Follett, Peter

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2009
Publication Date: 10/1/2009
Citation: Chen, N.J., Wall, M.M., Roboert, P.E., Follett, P.A. 2009. Variation in Sharwil avocado maturity during the harvest season and resistance to fruit fly infestation. HortScience. 44(6):1655-1661.

Interpretive Summary: Interpretive Summary: Avocados cannot be exported from Hawaii without a quarantine treatment to prevent the spread of fruit flies. Research on the maturity and infestability of ‘Sharwil’ avocados was conducted to support development of a systems approach for quarantine security of exported fruit. The time of harvest within a production season impacted ‘Sharwil’ avocado quality. Late season fruit had higher dry matter and oil contents, were smaller in size, and had a shorter shelf life than early and mid-season fruit. Avocado was a poor fruit fly host immediately after harvest, but became an increasingly favorable host as fruit ripened. The rate of fruit fly infestation was similar among early, mid- and late season fruit. The results will be used to develop a maturity standard for 'Sharwil' avocados, and to develop guidelines for postharvest practices of a systems approach for quarantine security.

Technical Abstract: Technical Abstract: Avocados cannot be exported from Hawaii without a quarantine treatment to prevent the spread of fruit flies. Research on the maturity and infestability of ‘Sharwil’ avocados was conducted to support development of a systems approach for quarantine security of exported fruit. The relationship between fruit dry matter content and oil content throughout the harvest season was determined for ‘Sharwil’ avocados grown at three orchard elevations over two production seasons. Also, infestability by Mediterranean fruit fly and oriental fruit fly was measured throughout the harvest season and during fruit ripening. There were minor differences in fruit quality for ‘Sharwil’ avocados harvested in 2007 and 2008 from the three sites, suggesting that fruit quality can be consistent from one year to the next, regardless of orchard elevation. All harvested avocados ripened normally, regardless of year, orchard location, or harvest season. However, the time of harvest within a production season impacted ‘Sharwil’ avocado quality. Late season fruit had higher dry matter and oil contents, were smaller in size, and had a shorter shelf life than early and mid-season fruit. The dry matter and oil contents of individual avocados were highly correlated (r = 0.97). The increase in oil content had no effect on the flavor or texture of the fruit, which did not change throughout the season. The ‘Sharwil’ avocado typically had high oil content, averaging 22.3% of its fresh weight. Avocado was a poor fruit fly host immediately after harvest but became an increasingly favorable host as fruit ripened. In 2007, no fruit flies emerged from a total of 450 field-collected harvest mature fruit, nor did any fruit flies emerge from forced infestation tests. In 2008, when fruit were exposed to flies on the day of harvest, none were infested by Mediterranean fruit fly, and only 2 fruit out of 48 were infested by oriental fruit fly. Although fruit increased in oil content and dry matter as the season progressed, this did not correlate with fruit fly infestability, as attack rates were similar among early, mid- and late season fruit. The results could be used to develop a maturity standard for Sharwil avocados based on dry matter content at harvest, and to develop guidelines for postharvest practices of a systems approach for quarantine security.