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- Author or Editor: Jorge B. Retamales x
Bitter pit is the most important physiological disorders for apples in Chile. During the 1995–96 season, the predictive capacity of bitter pit through magnesium infiltration of the fruit in commercial orchards of three locations in South Central Chile: San Fernando (SF), Curico (CU), and San Javier (SJ) was established. Three orchards were chosen in each location and for each cultivar; fruit were collected 60, 40, and 20 days before commercial harvest. Fruit were infiltrated for 2 min with magnesium chloride at 0.05 M using vacuum levels of 500 or 100 mm Hg for `Granny Smith' and `Braeburn', respectively. The predictive capacity (correlation between predicted and effective bitter pit—after 90 days at 2°C + 10 days at 18°C) increased closer to harvest; with regards to location: SF > CU > SJ. Bitter pit-like symptoms, caused by Mg infiltration stabilized 16 days after infiltration. Bitter pit incidence was better predicted than severity. Bitter pit was better predicted for `Granny Smith' than for `Braeburn'.
`Bluecrop' highbush blueberries (Vaccinium corymbosum L.) received various N fertilizer treatments for 5 years. Treatments were evaluated by measuring berry yields and leaf N levels annually and bush size after 5 years. Nitrogen fertilizers increased yields and leaf N levels compared with nonfertilized controls. Split applications of urea (half applied at budbreak, half at petal fall) resulted in 10% higher yields than the same amount in a single application at budbreak. Urea and two controlled-release fertilizers (CRF) with different dissolution rates (3 to 4 months, 8 to 9 months) resulted in similar yields and leaf N levels when compared at the same rate of N. The dissolution rate of the CRF materials did not affect yields or leaf N levels.
AC 94377 (alone and in combination with an auxin), GA3, and BA were evaluated for induction of parthenocarpy and subsequent retention of sour cherry (Prunus cerasus L. ‘Montmorency’) fruit. The persistence of AC 94377-treated fruit was enhanced by addition of CFPA or NAA, persistence and growth being greatest with AC 94377 (3.0 × 10−3 m) + CFPA (7.5 × 10−5 m). CFPA alone (7.5 × 10−5 m) often prevented abscission of flowers, but failed to induce significant fruit growth. Parthenocarpic fruit weighed 30-40% less than seeded fruit. Abscission of parthenocarpic fruit occurred primarily during June drop, and was reduced by an additional application of AC 94377 + CFPA with or without GA3 3 weeks after bloom. AC 94377 and NAA sprayed 2 and 3 weeks after full bloom did not affect the magnitude of June drop of open-pollinated fruit. The rate of fruit abscission was related to time after application, presence or absence of seeds, and relative position between seeded and parthenocarpic fruit. When AC 94377, GA3, and CFPA were applied in lanolin paste to defruited pedicels, only mixtures including CFPA reduced the abscission rate significantly. Chemical names used: l-(3-chlorophthalimido)-cyclohexanecarboxamide (AC 94377); 2-chloro,4-fluorophenoxyacetie acid (CFPA); N-(phenylmethyl)-lH-purin-6-amine (BA); gibberellic acid (GA3); 1-naphthaleneacetic acid (NAA).
Calcium gradients were established in firm (`Bluecrop' and `Blueray') and soft (`Ivanhoe') highbush blueberry (Vaccinium corymbosum L.) fruits from a 7-year-old planting at La Union, southern Chile. Manual firmness measurements established that `Ivanhoe' fruit was softer than either `Bluecrop' or `Blueray'. In all varieties, Ca concentrations were: seed > pulp > epidermis; opposite trends were found for K+Mg/Ca ratios. Seed number and Ca concentration in the pulp were negatively correlated in `Bluecrop' and `Ivanhoe', but not in `Blueray'. In a related experiment, the response of `Bluecrop' to preharvest sprays of two calcium sources (chloride and nitrate) in four doses (0, 47.5, 35, or 190 g Ca/100 liters of water) was studied; dose and source interactions were not significant. Both calcium sources affected fruit Ca concentrations similarly;l calcium applications, either as nitrate or chloride, increased Ca significantly in epidermis and seed; the highest dose was required to raise significantly Ca concentrations in the pulp. K+Mg/Ca ratios in nitrate- or chloride-treated fruit were: pulp > seed > epidermis.
To study the efficiency of fertilizer use by highbush blueberry (Vaccinium corymbosum L.), four mature ‘Bluecrop’ plants were treated before budbreak (21 Apr.) with soil applications of 15N-enriched urea at a rate equivalent to 40 kg N/ha. Leaf samples were collected at 1- to 4-week intervals during the season and whole plants were harvested at the end of the growing season (22 Sept.). Different plant components were separated, dried, weighed, and analyzed by mass spectrometry. Fertilizer-derived N was observed in leaves 2 weeks after application. The percentage of N from the fertilizer peaked 3 weeks after application (16.5%) and declined to ≈11% shortly thereafter. Plants recovered 32% of applied N by the end of the growing season. Leaves accounted for 32% of this total. Shoot tissue also accounted for 32% of fertilizer-derived N in the plant, with the highest percentage accumulating in young shoots. Less than 15% of fertilizer N remained in the soil at the end of the season.
Bitter pit (BP) is the main physiological disorder of apples in Chile. Its incidence affects pre- and postharvest handling of the fruit and the profitability of this species. Since 1991, its control and prediction have been studied by this research team through field and laboratory trials. The BP incidence is linked to the fruit Ca concentration; however, fruit Ca analysis has not adequately predicted BP incidence in postharvest. Several authors have proposed Ca/Mg antagonism, which has been the basis to develop a predictive method through fruit Mg infiltration (IMG) 40 days before harvest. IMG has been massively used for two seasons in Chile, with 375 samples processed in 1997 and 1170 in 1998. The industry has been increasing its proportion of the samples processed, from 22% in 1997 to 71% in 1998. The most prominent varieties are `Granny Smith' (GS) > `Braeburn' (BR) > `Royal Gala' (RG) > `Red King Oregon' (RKO). The massive use of IMG has obtained predictive capacities (r 2 between BP predicted and BP after 3 months regular cold storage) of 0.8 for `Fuji'; 0.7 for GS, BR, and RG; and 0.58 for RKO. (This reduction in the predictive capacity with regards to the previous research under controlled conditions would, in part, be due to problems in obtaining fruit samples: non-uniform fruit size, inadequate sampling dates, diverse fruit numbers, etc.) Developments are underway to increase the geographical coverage of the service, the predictive capacity of the method for certain cultivars and productive areas and the number of samples processed.
Parthenocarpic fruit development was induced in ‘Montmorency’ sour cherry (Prunus cerasus L.) with AC 94377. The biological activity of AC 94377 was increased significantly by NAA. The development (Stages I, II, III, “June drop”, ripening) of parthenocarpic fruit was similar to that of open pollinated controls except for smaller fruit size. Ovules enlarged during Stage I in AC 94377-induced parthenocarpic fruit, but lacked embryos; all ovules aborted during Stage II or III of fruit development. The primary action of NAA appeared to reduce abscission of AC 94377-treated ovaries with no significant effect on fruit size. Chemical names used: 1-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (6-BA); 1-(3-chlorophthalimido)-cy-clohexanecarboximide (AC 94377); polyoxyethylene sorbitan monooleate (Atlox BI).