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Tracie K. Matsumoto, Mike A. Nagao and Bruce Mackey

Flower induction of longan (Dimocarpus longan) with potassium chlorate has improved the availability of longan fruit, but potassium chlorate is potentially explosive and often difficult to purchase, transport, and store. Previous reports suggested that hypochlorite enhances natural longan flower induction. This study is the first to demonstrate that chlorite- and hypochlorite- (bleach) induced off-season longan flowering is similar to chlorate-treated trees. Hypochlorite induction of flowering with bleach was likely the result of chlorate in the bleach solution. Chlorate was present in the leachate from potted longan trees treated with bleach and was detected in bleach before soil application. The quantity of chlorate found in bleach induced flowering to the same or greater extent as equivalent quantities of potassium chlorate, suggesting chlorate is an a.i. responsible for longan flowering.

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Laurie G. Houck, Joel F. Jenner and Bruce E. Mackey

Commercially packed lemons (Citrus limon (L.) Burm.), grapefruit (C. paradisi Macfayden) and oranges (C. sinensis (L.) Osbeck) from CA and AZ were fumigated in corrugated fiberboard shipping boxes with methyl bromide (MB) at doses efficacious for controlling various postharvest insect pests. Fruit developed no rind injury when fumigated at 24 or 32 g MB/m3 for 2 hr at 21C. At 40 g MB fruit developed slight to moderate peel injury, and sometimes there were more decayed fruit. More rind injury developed at 48 gm MB, the injury was more severe, and there were more decays. Curing fruit for 3-4 days at 15-20C before fumigation, and extending the aeration period after fumigation from a few hours to 1 or 3 days reduced fruit injury. Early-season fruit were not injured as severely as late-season fruit. Lemons picked with green-colored peel but fumigated after they turned yellow (by holding at 13C for 4-10 weeks to degreen) were not injured as much as silver or yellow lemons.

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David Obenland, Paul Neipp, Bruce Mackey and Lisa Neven

Yellow- and white-fleshed peach [Prunus persica (L.) Batsch] and nectarine [Prunus persica (L.) Batsch var. nectarina (Ait) Maxim.] cultivars of mid- and late-season maturity classes were subjected to combined controlled atmosphere–temperature treatment system (CATTS) using heating rates of either 12 °C/hour (slow rate) or 24 °C/hour (fast rate) with a final chamber temperature of 46 °C, while maintaining a controlled atmosphere (CA) of 1 kPa oxygen and 15 kPa carbon dioxide. Fruit seed surface temperatures generally reached 45 °C within 160 minutes and 135 minutes for the slow and fast heating rate, respectively. The total duration of the slow heating rate treatment was 3 hours, while 2.5 h was required for the fast heating rate treatment. Following treatment the fruit were stored at 1 °C for either 1, 2, or 3 weeks followed by a ripening period of 2 to 4 d at 23 °C and subsequent evaluation of fruit quality. Fruit quality was similar for both heating rate treatments. Compared with the untreated controls, CATTS fruit displayed higher amounts of surface injury, although increased injury was only an important factor to marketability in cultivars that had high amounts of surface injury before treatment. The percentage of free juice in the flesh was slightly less in CATTS fruit early in storage but was often greater in treated fruit toward the end of the storage period. Slower rates of softening during fruit ripening were apparent in CATTS fruit. Soluble solids, acidity, weight loss and color all were either not affected or changed to a very small degree as a result of CATTS. Members of a trained sensory panel preferred the taste of untreated fruit over fruit that had been CATTS but the ratings of treated and nontreated fruit were generally similar and it is unclear whether an average consumer could detect the difference. Although further work needs to be done regarding the influence of CATTS on taste, it otherwise appears that CATTS does not adversely affect the marketability of good quality fruit and therefore shows promise as a nonchemical quarantine treatment for peaches and nectarines.

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David Obenland, Dennis Margosan, Joseph L. Smilanick and Bruce Mackey

Navel oranges (Citrus sinensis) were sorted into four groups under ultraviolet illumination in commercial packinghouse black light rooms based upon the amount of fluorescence visible on each fruit to determine if fluorescence was predictive of peel quality. The groups corresponded to fruit with 1) little or no fluorescence (group 0), 2) low fluorescence (group 1), 3) moderate fluorescence (group 2), and 4) large fluorescent areas (group 3) that were indicative of developing decay lesions. Identification and elimination of group 3 fruit in black light rooms is a common practice now, but the other groups pass through these rooms. Six tests were conducted over a 2-year period during different times in the mid to late navel orange season. Fruit were visually evaluated for peel quality within 24 hours of their initial segregation into fluorescence groups and again following 3 weeks of storage at 15 °C. Peel quality assessment was based upon commercial grading practices, and the fruit were placed into fancy, choice, juice, or decay classes. Fruit with low to no peel fluorescence (groups 0 and 1) had numerous fancy-grade fruit and few juice- and decay-grade fruit in comparison with the other two groups. In contrast, fruit with moderate fluorescence (group 2) were of poor peel quality. In the initial evaluation, this group had 28% fewer fancy fruit and 19% more juice fruit than did group 0. During storage, group 2 fruit declined markedly in quality and numerous fruit of group 2 in the choice and juice classes decayed; the percentage of decayed fruit increased from 1% initially to 29% after 3 weeks of storage. Navel oranges in group 3, with numerous and obvious fluorescent decay lesions, mainly consisted of either juice grade or decayed fruit; 70% of group 3 decayed after 3 weeks. In addition to removing fluorescing fruit that have obvious indications of decay (group 3), it would be advantageous to remove or otherwise recognize that fruit with moderate levels of fluorescence (group 2) are also of lower quality and that they should not be selected for long storage or distant transport. Their identification may be most practical with an automated system using machine vision and ultraviolet illumination.

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Tracie K. Matsumoto, Francis T.P. Zee, Jon Y. Suzuki, Savarni Tripathi, James Carr and Bruce Mackey

Papaya ringspot virus (PRSV) is a devastating disease that has a detrimental impact on both commercial papaya production and Caricaceae germplasm conservation. In 1998, the PRSV coat protein transgenic line 55-1 and derived progeny were released to growers in Hawaii. The transgenic varieties have provided durable and practical control of the disease that have saved the papaya industry. However, like with transgenic crops throughout the world, there is public concern about the possibility of cross-contamination of these transgenic materials into nontransgenic lines. As the designated germplasm repository for Caricaceae, we are responsible for maintaining the genetic integrity of each accession. Therefore, we have developed a protocol using polymerase chain reaction for detection of the adventitious presence of the 55-1 transgene insertion event in both parental plants and their progeny seed populations. This protocol assures a 99.9% confidence level of obtaining seeds that are 99.5% transgene-free. The protocol developed in this study is not typical for most seed validation techniques because there is a higher than normal producer risk resulting from the potential of large numbers of seeds not meeting the stringent criteria. However, we believe this is necessary to ensure the genetic integrity of seeds stored in the repository.