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  • Author or Editor: Zhentu Ying x
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Floral induction of mango is determined by interaction of a short-lived, florigenic promoter that is up-regulated in leaves during exposure to cool temperatures and an age-dependent vegetative promoter at the time that initiation of shoot growth occurs. Research conducted during the past flowering season demonstrated that 1/4 of a leaf per stem was sufficient to stimulate flowering in 100% of the tested stems. Three or more leaves on a donor stem of an isolated branch also bearing five defoliated stems induced flowering on all six stems. One leaf on the donor stem was sufficient to induce flowering in all of the donor stems and most of the five defoliated stems, and 1/2 leaf on the donor stem stimulated flowering in that stem and in less than 1/2 of the defoliated stems. Stems that did not flower initiated vegetative shoots instead. Flowering occurred on those stems that were inserted into main branches in the same phylotaxic position as the leaf. Evidence suggests that leaves are capable of producing far greater amounts of florigenic promoter during floral inductive conditions than needed for induction of buds and that the promoter can move great distances in phloem aligned in the same phylotaxic position as the source leaf.

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The synchronously dichogamous flowering behavior of avocado has historically been assumed to promote cross-pollination. Preliminary studies in southern California have revealed that self-pollination is more typical. The primary objective of the California research is to determine the paternity of individual fruit sampled during early and late fruit development using SSR markers. Cultivars included Hass as the primary cultivar and Bacon, Ettinger, Fuerte, Harvest, Lamb Hass, Marvel, Nobel, SirPrize, and Zutano serving as cross-pollinizing cultivars. We were able to: 1) estimate proportions of self- and cross-pollinated `Hass' fruit with cultivars planted in rows of varying proximity to the `Hass' rows; determine if the proportion of outcrossed fruit increased during maturity due to preferential abscission of self-pollinated fruit; and 2) determine if there is preferential retention of fruit cross-pollinated by a specific cultivar during maturation. On average, cross-pollination by any individual cultivar in 2004 was 6% or less in marble-sized fruit. Over 70% of the fruit were self-pollinated. This is greater than the proportion of self-pollination (about 30%) observed in near-mature fruit harvested in the previous year, 2003. Proportions of marble-sized fruit pollinated by each cultivar within each row were compared to the proportions of self or cross-pollinations in fruit harvested from the same trees at near-maturity. We observed about a 10% increase in proportion of self-pollinated fruit and a concomitant decrease in retained fruit derived from cross-pollination. Self-pollination appears to be the dominant mode of pollination. These preliminary results indicate that trees benefit from it, perhaps in preference over cross-pollination.

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