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R. Porat, B. Weiss, I. Zipori and A. Dag

The local guava (Psidium guajava) variety cultivated in Israel, named Ben Dov, emits a strong odor and suffers from a short postharvest life. To address these problems, we initiated a guava breeding program, and identified two new varieties, the pink-flesh King and the white/yellowish-flesh Omri, that have much better storage lives and emit fewer odors. Physiological characterization of their ripening process revealed that the traditional variety Ben Dov exhibited a classic climacteric behavior, whereas the new variety King had a suppressed-climacteric phenotype, and Omri was apparently nonclimacteric and did not exhibit any increases in respiration and ethylene production rates during ripening. Furthermore, differing concentrations of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were required to inhibit ripening in the various varieties: a high 1-MCP concentration of 500 nL·L−1 was required to delay ripening and to prolong postharvest storage life of the climacteric variety Ben Dov; a moderate concentration of 250 nL·L−1 inhibited ripening of the suppressed-climacteric variety King; and a low concentration of just 100 nL·L−1 was sufficient to inhibit ripening of the nonclimacteric variety Omri. The results of this study indicate that different guava varieties may pursue distinctive climacteric behaviors: the suppressed-climacteric variety and, to a greater extent, the nonclimacteric variety, have longer storage lives and are more sensitive to 1-MCP than the traditional variety.

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A. Dag, D. Eisenstein, S. Gazit, R. El-Batsri and C. Degani

Postzygotic self-incompatibility has been reported in several Indian mango (Mangifera indica L.) commercial cultivars. Floridian cultivars, on the other hand, have been planted in solid blocks and seem to be self-fertile. Isozyme analysis enabled us to determine outcrossings rates at the fruitlet and fruit stages in the Floridian `Tommy Atkins' (`Tommy'). Two commercial mango orchards consisting of adjacent solid blocks of `Maya' and `Tommy' were studied. This combination offered a unique opportunity to identify each individual fruitlet or fruit as selfed or outcrossed by TPI isozyme analysis. A consistent and significant increase in outcrossing rate during fruit development was found: the average outcrossing rate increased from 10% and 13% in fruitlets to 66% and 73% in mature fruit in the two `Tommy' blocks surveyed. This 6-fold increase is the result of selective abscission of selfed progeny. A significant inverse correlation was found between the distance of `Tommy' trees from the `Maya' block and the outcrossing rate in mature fruit. No significant correlation between distance from `Maya', or outcrossing rate, and yield was observed, suggesting that the practice of planting `Tommy' in solid blocks is sound.