No abstract

-Introduction. Canada is an important avocado importer from Mexico. For most of the harvest season, fruit reach adequate pulp dry matter content, ripen properly and, consequently, quality and shelf life are excellent. However, after January, fruit dry matter content increases and blackened skin occurs. Shipments to Canada containing blackened fruit are rejected because this characteristic is wrongly associated with low pulp firmness and short shelf life. The objective of our research was to determine the effect of harvest time and ripening degree on initial quality and shelf life of Hass avocado. Materials and methods. Fruit were harvested from October 2007 to April 2008, and grouped into five ripening categories according to the degree of blackened skin. Fruit were then refrigerated for 7 d to simulate shipment to Canada. Thereafter, fruit were stored under simulated market conditions until they reached the edible ripening stage. Dry matter content was calculated only at the beginning of the storage period while quantification of weight loss, fruit with blackened skin, pulp firmness, and pulp color was done at the beginning of the storage period, at the end of the refrigeration period, and every three days during market conditions. Results and discussion. Dry matter content, skin color and pulp hue angle significantly increased with harvest date and ripening degree. Weight loss decreased with harvest date but increased with ripening degree, while firmness was affected by harvest date but was not associated with ripening degree. Conclusion. There is no reason to reject or downgrade blackened fruit, since quality and shelf life are not affected.Mexico / Persea americana / fruits / ripening / dry matter content / weight losses / color / peel / firmness Effet de la date de récolte et du degré de maturation sur la qualité et la durée de vie de l'avocat Hass au Mexique.Résumé -Introduction. Le Canada est un important importateur d'avocats en provenance du Mexique. Pour la plupart des saisons de récolte, les fruits atteignent une teneur adéquate en matière sèche de la pulpe, mûrissent correctement et, par conséquent, leur qualité et leur durée de vie sont excellentes. Toutefois, après janvier, la teneur en matière sèche des fruits augmente et un noircissement de la peau se produit. Les expéditions vers le Canada contenant des fruits noircis sont rejetées parce que cette caractéristique est faussement associée à une faible fermeté de la pulpe et une courte durée de conservation. L'objectif de notre recherche a été de déterminer l'effet de la date de récolte et du degré de maturation sur la qualité initiale et la durée de vie de l'avocat Hass. Matériel et méthodes. Des fruits ont été récoltés d'octobre 2007 à avril 2008 et regroupés en cinq catégories de maturation en fonction du degré de noircissement de la peau. Ces fruits ont été ensuite mis au réfri-gérateur pendant 7 jours pour simuler une expédition au Canada. Ensuite, les fruits ont été entreposés dans des conditions simulant leur mise en marché jusqu'à ...

Several studies were undertaken in commercial nonirrigated `Hass' avocado orchards under the subhumid semiwarm subtropical climate of the state of Nayarit, Mexico, with the following objectives: 1) to determine the frequency and intensity of vegetative shoot flushes and their contribution to the production of floral shoots, 2) to quantify the effect of tree fruit load on the occurrence of vegetative shoot flushes during the year and the relationship between vegetative and reproductive shoot number during flowering, and 3) to determine the time when apical buds borne on the major vegetative shoot flushes reached irreversible commitment to flowering (floral determination) through the use of shoot defoliation and girdling. Data trees were selected in two orchards based on their current crop load. Four to five branches per tree were tagged, and the number and intensity of vegetative flushes that developed during 2 years, as well as the type of growth produced by apical buds of shoots of different ages, were recorded at the end of the winter bloom periods for two separate years, 1999 and 2001. In a separate experiment using a different set of trees, winter and summer flush shoots were defoliated (year 1) or defoliated and girdled (year 2) at different stages of bud development from September to January in each case. Four vegetative flushes occurred each year. The winter flush that emerged in Feb. 1998 made the greatest contribution to the 1999 winter bloom—76.5% of the shoots produced floral shoots. Contributions of the summer 1 (late July 1998), summer 2 (early Aug. 1998), and summer 3 (late Aug. 1998) flushes to flowering were intermediate. A total of 30.6%, 36.4%, and 19% of the shoots produced floral shoots respectively. All four vegetative flushes produced a similar number of vegetative shoots during winter bloom. Evaluation of the 2001 winter bloom for trees with high (>95 kg fruit/tree) and low (<70 kg fruit/tree) crops showed no effect of tree fruit load on the production of vegetative or floral shoots by winter or summer vegetative flushes. Irrespective of time of treatment (shoot defoliation and girdling) or shoot age, irreversible commitment to flowering of apical buds occurred by 15 Oct., and this stage was associated with an average of 27.5 chilling days (temperature, ≤19 °C) for both years. Buds irreversibly committed to flowering were closed and pointed, with partial senescence of bud scales. Anatomically, the buds showed a convex primary axis meristem and four secondary axis floral shoot meristems.

No abstract

No abstract