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An efficient procedure for the conservation of mature American elm (Ulmus americana L.) trees that have survived the epidemics of Dutch elm disease and are potential sources of disease resistance is reported. The model utilizes in vitro proliferation of fresh and dormant buds from mature trees for cloning nearly 100 year old American elm trees. The key factors that influenced sustained growth and multiplication included optimization of culture process and auxin metabolism in the source tissue. Blocking the action of endogenous auxins through the addition of antiauxin in the proliferation medium was crucial for high multiplication rate and optimum shoot development. Addition of antiauxin also mitigated the decline in productivity observed with multiple subcultures, which will enable long-term conservation of selected germplasm. The most effective medium for long-term proliferation contained 5.0 umol/L p-chlorophenoxyisobutyric acid with 2.2 umol/L benzylaminopurine and 0.29 umol/L gibberellic acid. Medium with 2.5 umol/L indole-3-butyric acid was the best for rooting microshoots (89%). Rooted plantlets were readily acclimatized to the greenhouse environment with a 90% survival rate. The strategy developed for American elm will aid in increasing multiplication of resistant clones, facilitate long-term conservation of elite genotypes, and also provide an approach to improve conservation of other endangered tree species. Resume: Une methode efficace pour conserver les ormes d'Amerique (Ulmus americana L.) matures qui ont survecu aux epidemies de la maladie hollandaise de l'orme et qui constituent des sources potentielles de resistance a la maladie est rapportee. Le modele utilise la propagation in vitro de bourgeons frais et dormants provenant d'arbres matures pour cloner des ormes d'Amerique qui ont presque 100 ans. Les facteurs cles qui assurent une multiplication et une croissance soutenues incluent l'optimisation du processus de culture et du metabolisme des auxines dans les tissus souches. Il etait essentiel de bloquer l'action des auxines endogenes par l'addition d'antiauxine dans le milieu de propagation pour obtenir un taux eleve de multiplication et un developpement optimal des pousses. L'addition d'antiauxine a egalement attenue le declin de productivite observe a cause des multiples souscultures, ce qui rendra possible la conservation a long terme du germoplasme selectionne. Le milieu le plus efficace pour la propagation a long terme contenait 5,0 umol/L d'acide p-chlorophenoxyisobutyrique avec 2,2 umol/L de benzylaminopurine et 0,29 umol/L d'acide gibberellique. Le milieu contenant 2,5 umol/L d'acide indole 3-butyrique etait le meilleur milieu pour enraciner les micropousses (89 %). Les plantules enracinees s'acclimataient facilement en serre avec un taux de survie de 90 %. La strategie qui a ete developpee pour l'orme d'Amerique pourra contribuer a accro?tre la multiplication des clones resistants, a faciliter la conservation a long terme de genotypes elites et egalement a fournir une approche pour ameliorer la conservation d'autres especes d'arbre menacees. [Traduit par la Redaction], Introduction The American elm (Ulmus americana L.) is a North American species belonging to the family Ulmaceae and is highly prized as an urban landscaping tree admired for its arching [...]

The study objective was to determine the effects of field application of hexanal on pre-harvest market attributes of orange (Citrus sinensis L.) fruits. The first factor was hexanal concentration (0.01, 0.02, 0.04% and controls – untreated fruits), the second factor consisted of time of hexanal application prior to fruit harvest (7, 21, 42 and 60 days to harvest) and the third factor was season (1st and 2nd season). Tested orange varieties were Early Valencia ('Msasa'), Jaffa and Late Valencia varieties. A fruit tree for each orange variety constituted a treatment for hexanal application and time of its application prior to fruit harvest. The results show that hexanal application at 0.01, 0.02 and 0.04% equally improved fruit marketable yields by increasing fruit firmness and number of marketable fruit of Early Valencia, Jaffa and Late Valencia varieties. Number of marketable fruit increased by 34.89%, 34.04% and 42.48% over the controls for Early Valencia, Jaffa and Late Valencia, respectively. Similarly, fruit firmness increased by 11.38, 11.03 and 11.92 N/mm2 over the control for Early Valencia, Jaffa and Late Valencia, respectively. It is recommended that farmers should treat Early Valencia, Jaffa and Late Valencia with hexanal at 0.01% in order to increase marketable yield and fruit quality. [ABSTRACT FROM AUTHOR]

Experiments were conducted to assess the effects of hexanal, calcium chloride, and smoke on the post-harvest quality of oranges under ambient (room) temperature (28±2°C) and reduced temperature storage (18±2°C) conditions on two varieties of sweet orange (Citrus x sinensis (L.) Osbeck) cvs 'Msasa' and 'Jaffa'. Fruit were dipped in enhanced freshness formulation (EFF) containing hexanal as the key ingredient at 0.01%, 0.02%, and 0.04% (volume/volume), or calcium chloride solution at 1%, 2%, and 4% (weight/volume) for five minutes each, or subjected to a smoking regime, simulating a popular traditional practice, by burning 0.5 kg, 1.0 kg, and 1.5 kg of dried banana leaves, or left untreated (control). Various parameters including physiological weight loss, fruit firmness, total soluble solids (TSS), titratable acidity (TA), and the TSS/TA ratio were assessed to determine effects on post-harvest quality of fruit. Results indicate that hexanal and calcium chloride treatments significantly (p < 0.001) reduced physiological weight loss, maintained fruit firmness and significantly higher TSS in both varieties compared to smoke treatment and untreated controls. Reduced temperature storage also significantly (p < 0.001) lowered physiological weight loss of hexanal- and calcium chloride-treated oranges. Based on the results of this study, post-harvest dip treatments with hexanal solution at 0.02% or calcium chloride solution at 2% coupled with reduced temperature storage at 18°C are recommended to maintain the quality of fresh oranges in Tanzania. On the contrary, the application of smoke is highly discouraged as it reduces the quality of oranges. [ABSTRACT FROM AUTHOR]

A laboratory study was undertaken to determine the effects of a nano-emulsion carrying hexanal, an enhanced freshness formulation (EFF), as a post-harvest dip technology to minimize the post-harvest losses and to extend the shelf life of bananas. The banana fruits were harvested at three maturities (95%, 85%, and 75%), dipped or not dipped in the EFF, and studied under both ambient and reduced temperature storage conditions. During the experiments, the fruit's physical, physiological, and biochemical parameters were periodically evaluated. The treated fruit had lower physiological loss of weight and higher firmness throughout the study period, regardless of maturity level at the start. Treated fruit had higher total soluble solids and total sugars, and less acidity indicating improved fruit quality during storage, in addition to an extended shelf life. High resolution imaging using scanning electron microscopy showed that EFF-treated fruit exhibited well maintained structural lenticels on the fruit skin and deposition of starch granules in the fruit pulp, regardless of maturity level at the start. Overall, the results clearly indicated that the EFF-treated banana fruit were delayed in the ripening process and had an extended shelf life of up to six days in ambient conditions and nine days in cold storage conditions. Post-harvest dipping using hexanal formulation is a potential technology that could be adopted in pack houses for domestic and export markets. [ABSTRACT FROM AUTHOR]