ARS | Publication request: In Situ Seasonal Study of the Volatile Production of Almonds (Prunus dulcis), var. 'Nonpareil' and Relationship to Navel Orangeworm

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 2009
Publication Date: April 3, 2009
Citation: Beck, J.J., Merrill, G.B., Higbee, B.S., Light, D.M., Gee, W.S. 2009. In Situ Seasonal Study of the Volatile Production of Almonds (Prunus dulcis), var. 'Nonpareil' and Relationship to Navel Orangeworm. Journal of Agricultural and Food Chemistry, DOI:10.1021/jf9003187.

Interpretive Summary: The Nonpareil almond variety, Prunus dulcis, represents the most widely planted almond variety in the Sacramento and San Joaquin valleys of California and comprise ca. 37% of the total acres of varieties grown. California is the top producer of almonds, supplying 80% of the world¿s needs, and 100% of the U.S. market¿s supply. Approximately 5% of California¿s cropland is committed to almond. The navel orangeworm (NOW), Amyelois transitella, is an insect pest of California tree nuts. Its feeding damage lowers nut kernel quality resulting in extensive monetary loss to growers, producers, and shippers; thus, control of NOW has now become one of the top priorities of the California tree nut industry. There are numerous reports in the literature on both volatile and nonvolatile composition of various parts of some almond cultivars; nonetheless, the VOC emission of almonds of any one single cultivar has not been studied over the course of an entire growing season. This aspect is particularly relevant to research concerning NOW. Despite the continued presence of NOW, the identification of particular VOCs, or their relationship to NOW, has not been addressed. This study investigated the VOC emission of Nonpareil almonds in a single growing season from bloom to hull split. The VOC emission was measured in situ via an inert collection bag, and employing solid-phase microextraction (SPME) as the adsorbent medium. The collected VOCs were analyzed by gas chromatography-mass spectroscopy (GC-MS) and identified by their MS fragmentation patterns. The VOCs were subjected to electroantennogram (EAG) bioassays with both male and female NOW. This is the first report of the VOC emission from a single almond cultivar over the course of a growing season, and collected in situ. The report demonstrates the potential importance of these VOCs as background signaling volatiles to NOW and its attractants.

Technical Abstract: Nonpareil almonds, Prunus dulcis, account for the largest percentage of almond varieties grown in the Central Valley of California. Several studies have investigated the various nonvolatile and volatile components of various plant parts; however, the volatile organic compound (VOC) emission of almonds from a single cultivar has not been studied over the course of a growing season. This aspect is particularly relevant to research concerning the navel orangeworm (NOW), a major insect pest of almonds and other tree nuts. Despite the continued presence of NOW, the identification of particular VOCs, or their relationship to NOW, has not been addressed. The VOC emission of Nonpareil almonds was collected in situ over the course of a growing season by solid-phase microextraction (SPME). The VOCs (Z)-hex-3-enyl acetate, (Z)-hex-3-enyl butyrate, undecan-2-ol, '-bourbonene, and tetradecane were present for the majority of the days investigated. Several VOCs exhibited positive electroantennographic signals from male and/or female NOW moths.