RIPENING PHYSIOLOGY IN 'NAVAHO' THORNLESS BLACKBERRY FRUIT: COLOR, RESPIRATION, ETHYLENE PRODUCTION, SOFTENING, AND COMPOSITIONAL CHANGES

Authors: Perkins Veazie, Penelope; CLARK, J.R. - UNIVERSITY OF ARKANSAS; HUBER, D.J. - UNIVERSITY OF FLORIDA; Baldwin, Elizabeth - Liz

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Little is known about the ripening process of North American blackberry species. A knowledge of berry growth, sweetening, and softening is needed for quality maintenance as the commercial importance of fresh market blackberries increases. The 'Navaho' blackberry, a variety which has an excellent shelf life, was selected to study changes in respiration, ethylene and volatile production, softening, and compositional changes. Most changes in 'Navaho' blackberries occurred in the last week of berry growth and coincided with development of black fruit color. Ethylene production was very low and increased only in the last stages of ripening. Results indicate that a series of ripening events occur at a similar time in blackberries and appear to be regulated by a factor other than ethylene; removal of fruit when only partially black in color will not improve shelf life or quality.

Technical Abstract: Fruit were harvested from an erect, thornless blackberry (Rubus sp., cv Navaho) to study ripening changes. Soluble solids content increased between the red (unripe) and dull-black (overripe) stages of ripening while titratable acidity decreased sharply between the mottled and shiny-black ripeness stages. Anthocyanin content increased sharply between the mottle and shiny-black stages. Firmness of drupelet and receptacle tissues decreased between the mottled and shiny-black stages of ripeness. In whole blackberries, total uronic acids decreased, and water soluble uronic acids increased between the green-red and shiny-black ripeness stages. Volatile production paralleled ripening changes, and was highest in dull- black fruit, with alcohols and aldehydes predominating. Respiration of intact fruit maintained in water decreased between the green and red ripeness stages and increased at the mottled (part-black) and black ripeness stages. Ethylene production remained below 10 nmol.kg**-1#h **-1 until the dull-black (overripe) stage of maturity. Free 1- aminocyclopropane-1-carboxylic acid (ACC) and ACC oxidase did not increase in berries until the shiny-black stage, corresponding with the onset of detectable ethylene production. ACC oxidase activity decreased in the drupelet tissue (0.5 to 0.01 nmol kg**-1 h** -1) and increased in the receptacle tissue (2 to 3.8 nmol kg**-1.h**-1) as fruit changed from red to dull-black. These results indicate that ripening in blackberry fruit may be initiated in the receptacle tissue. Ripening in blackberry fruit is likely independent of ethylene, but ethylene may regulate berry detachment from pedicels, thus controlling timing of fruit harvests.