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  • Author or Editor: J. Siller-Cepeda x
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The scarce chilling accumulation during autumn and the high variability among years under desert conditions demands a high priority to study the interaction of chilling accumulated and hydrogen cyanamide rate to improve budbreak. Canes were collected at the onset of dormancy on 31 Oct, 1991 and stored at 4°C from 0 to 300 hours (CH). Additionally, cyanamide at 0.0, 0.025, 0.050, 0.100, 0.200, and 0.400M was sprayed to run-off every 50 CH and placed in a growth chamber (23±1°C) with additional light for budbreak evaluations. Final budbreak of control plants improved significantly with chilling accumulated from 12% on the controls up to 96% on 300 CH. Sixty percent budbreak occurred after the control plants reach 250 CH. Cyanamide rates ≤ to 0.2M increased budbreak above the control when chilling was ≤250 CH. After 300 CH, final budbreak was alike on all treatments, but cyanamide delayed budbreak. The most consistent treatments were 0.1 and 0.2M cyanamide rates (2 and 4% a.i. on adult vines). No significant differences were found among this treatments on final budbreak at all chilling levels; however, between 100 and 200 CH, cyanamide induced early budbreak.

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On-tree storage of Citrus has been a common practice to prolong marketing season, even for those fruits reaching legal maturity. Under this situation, fruit quality losses are dependent upon the length of stored period. On this work, we evaluated the effect mat on-tree storage had over the level and form of ascorbic acid, as well as, the quality of fruit harvested at different intervals after legal maturity. Treatments consisted on harvesting fruits at seven different dates beginning on 18 March (legal maturity) and on 6 May, 21 May, 23 June, 17 July, 28 August and 14 September, 1992. Quality variables evaluated were: diameter, ring thickness, weight, color (chroma, hue and value), firmness, pH, soluble solids, tritatable acidity, juice content, and ascorbic acid content and form. Fruit weight fruit and pH increased with harvesting date. Color in its three aspects decreased, indicative of value loss, change from yellow to green, and defined chroma colors. Citric acid drop drastically, and although degree Brix was almost constant, the Citric acid/Brix increased from 15 to 38, representing fruit taste loss. Ascorbic acid decreased, while its oxidized form increased with successive harvesting dates.

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On Sinaloa State, tomato growers test new varieties every year looking high yield, better quality and long shelf life. However, few studies are done to know the resistance to postharvest diseases. The objective was to identify postharvest pathogens that infect this new tomato varieties with characteristics rin, nor or normals (BR84, S211, S69, and S121). Fruits in two stages of maturity (pink and red) were harvested and stored under simulated marketing conditions (20°C and 80% RH). Pathogens found were aisled on PDA and identified under microscope. Different chemicals were tested to control pathogens [NaOCl; Ca(OCl)2; Supersana; iodine; Citrucidal; Captan; and water]. Six fungus species—Alternaria alternata, Fusarium oxysporium, Rhizopus stolonifer, Colletotrichum sp., Rhyzoctonia sp, and Phomopsis sp—were found on all varieties. BR84 fruit (rin type) harvested on pink stage were more resistant than red ones. S69 fruit (nor type) were more susceptible at the pink than at the red stage. S121 fruits (normal type) were equally susceptible at both stages of maturity. Least resistant variety to fungus infection at both stages of maturity was S211 (rin type). Citrucidal and Ca(OCl)2 gave the best control.

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Sinaloa tomato growers continuously evaluate new varieties, looking for better quality and long shelf life. Mutant fruit with the genes rin and nor offers both possibilities when crossed with normal fruit. Our study presents results of 16 tomato hybrid lines harvested from the field at the “turning” stage and stored under simulated marketing conditions (20°C and 80% RH). Twelve experimental hybrids were from the rin type, one from the nor type, two commercial hybrids were normal, and one commercial line from the rin type. Sampling was done every 2 days up to 16 days. Evaluations done included physical, chemical, and physiological determinations. Line S69 (nor type) had higher firmness compared to the others, while normal lines (S121 and S123) were the softest. S69 was the only hybrid that did not completed a red external color development. Experimental lines of the rin type presented acceptable development of red color, however, only normal lines (S121 and S123) reached the characteristic red color of tomato. Lines of the rin type (S172 and S200) lost more weight during marketing than normal ones. Pulp pH was higher on the experimental rin lines than on the commercial ones (BR84, S121 and S123). Not difference on the sugar: acid ratio among the lines was found. Only normal lines showed a climateric CO2 and C2H4 peak.

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México is an important mango producer. During its marketing is necessary to maintain fruit quality for long periods to access distant markets. Modified (MA) and controlled (CA) atmospheres are used in some tropical fruits to attain these goals. In this work, we evaluated Keitt mangoes quality under CA (low O2 ≤0.3%) and MA with three low density polyethylene (LDP) films (100, 200 and 300 mils) during six days. CA fruit treated and LDP packed were stored for 30 days at 10C. Every three days, samples from CA and MA were evaluated, and every ten days a lot of treated fruits were transferred to 20C to determine fruit quality changes. We found that both, CA and MA (using LDP) delayed weight and firmness losses. Fruits kept a good appearance with a significative delay of the maturity process. However, fruit packed with 200 and 300 mils LDP developed a fermented taste after 10 days at 10C. Our conclusions suggest that these treatments prolong marketing and storage life of “Keitt” mangoes.

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The nature of yield and quality losses for many fruits is dependent upon the time when water deficits occur in relation to fruit development. We evaluated the water stress effect applied at different stages of development on the quality and harvest date of 'Perlette' table grapes. Nine treatments based on amount of water applied by the grower (100%, 80% and 60%) and their combinations at two growth stages, fruit set to vérasion (F-V) and vérasion to harvest (V-H) were compared. Weekly samples of fruit were analyzed for diameter, weight, volume, soluble solids, tritatable acidity, pH, and pectin content. Harvest percentage at each date was used as precocity index. Significant differences were found on diameter and weight among treatments at various stages of development. The earliest and highest harvest percentage was for (F-V 80% and V-H 100%) treatment. High °Brix were obtained when the water volume was reduced after vérasion, but quality was poor. Chelator soluble pectins represented > 90% of total soluble pectins and was higher on the treatment (F-V 60% and V-H 60%) at harvest.

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