Citrus fruits are sensitive to low temperatures and this often results in the development of chilling injuries during postharvest storage. In order to gain more insight into the molecular mechanisms involved in the acquisition of fruit chilling tolerance, we initiated a grapefruit (Citrus paradisi, cv. Marsh Seedless) flavedo cDNA sequencing project and used it to identify a cDNA similar to other Poncirus trifoliata and Citrus unshiu dehydrin genes reported to be responsive to low temperatures. The grapefruit dehydrin cDNA, designated cor15, encodes a predicted polypeptide of 15.1 kDa, that is almost completely identical with other reported citrus dehydrin proteins, except that it contains two large amino acid repeats, whereas P. trifoliata COR11 has only one such repeat and P. trifoliata COR19 and C. unshiu COR19 have three repeats. Together, the various grapefruit, P. trifoliata and C. unshiu dehydrins form a closely related and unique dehydrin gene family that differs from most other plant dehydrins in having an unusual K-segment similar to that of gymnosperms and in having a serine cluster (S-segment) at an unusual position at the carboxy-terminus. The grapefruit cor15 gene is consistently expressed in the fruit peel tissue at harvest, but its message levels dramatically decrease during storage at 2 degrees C. However, a pre-storage hot water treatment, which enhances fruit chilling tolerance, elicited retention of the constant level of cor15 gene expression during cold storage and eliminated its decline. The hot water treatment had no inductive effect on cor15 gene expression when the fruit were held at non-chilling temperatures. The effects of other stresses, such as exposure to ethylene, UV irradiation and wounding, on cor15 gene expression, were temporary and persisted for 1-2 days after the treatments.

In this chapter, an overview of the general classifications of stored product insect pests (internal developers and external developers), and management of stored product insect pests through the application of fumigants and contact insecticides, and physical disinfestation methods is provided. Insect management through heat disinfestation of stored products and storage structures, effects of high temperatures on stored product insects, heat tolerance in stored product insects, and empirical methods and simulation models for obtaining thermal kinetic data for stored product insects are covered. The current status of research and development in heat disinfestation of stored products is described, focusing on convective heating, conductive heating, and electromagnetic energy. The heat disinfestation of structures, and the equipment used in the process are presented.

Two developmental stages of Ceratitis capitata (Wiedemann), 24-h-old eggs and third instars, 8 d after oviposition, were subjected to thermal exposures in a heating block system, at various temperatures of 46, 48, 50, and 52 degrees C to determine the thermal death kinetics of the insects. At these temperatures, 100% mortality was achieved by exposure of 300 C. capitata larvae for 60, 15, 4, and 1 min, respectively. The 0.5 order kinetic model had the best fit to the survival ratio for all the treatment temperatures, hence it was used for the prediction of the lethal times. The thermal death time (TDT) curves showed that the third instars were more heat-resistant than eggs, especially at the two low temperatures (46 and 48 degrees C). Under temperature-time combinations that did not result in complete kill, the thermal mortality for eggs was also significantly higher than that for third instars. The activation energy values calculated from the TDT curves were 490.6 and 551.9 kJ/mol, respectively, for thermal death of eggs and third instars.

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This chapter focuses on the following: commercially used quarantine heat treatments (vapour heat, forced hot air, and hot water immersion); quarantine treatment protocols; quarantine security statistics; factors that directly affect the research, development, approval and implementation of quarantine heat treatments (number of target species and their life stages, location of the target pest on or in the commodity, the host status of the commodity in nature, thermal diffusivity of the commodity, physiological or morphological characteristics of the commodity, treatment tolerance in pests, economic feasibility of the treatment under commercial conditions, the difficulty of commercial treatment applications or regulatory monitoring, and treatment tolerance in commodities); effects on heat treatments on the quality of the commodity; experimental heat treatment equipment and heat treatment research; and commercial heat treatment equipment and facilities. Fruit flies are largely covered.

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