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Carrot (Daucus carota L.) root cracking and breakage during harvest and handling operations result in serious losses. The environmental and management factors affecting carrot cracking and breakage susceptibility were investigated in a survey of fields and a series of trials conducted in California from 2000–02. Roots, leaves and soil were collected from a total of 31 commercial fields of `Sugar Snax' carrot, and soil texture and plant and soil fertility status were determined. Soil moisture was monitored in 10 fields to determine whether irrigation management was correlated with root cracking susceptibility; in 4 of these fields roots were harvested both before 0800 hr and at 1300 hr on the same day to directly compare the effects of root water status on cracking. The effect of N fertilization on cracking and breakage was investigated in 5 field trials. The relative susceptibility of 10 cultivars to cracking and breakage was also compared. Cracking susceptibility was determined with an impact test, and breakage with a loading test. Roots were selected by size (18 to 24 mm diameter) and cooled to 5 °C before testing. The percentage of roots cracked in the impact test varied from 7% to 75% among survey fields. Initial root water potential was not correlated with cracking incidence. However, after hydrating roots to minimize differences in water potential among fields, cracking incidence was correlated with turgor potential (r = 0.41). Soil sand content and mean air temperature in the 30 days preceding harvest were also correlated with cracking (r = –0.48 and 0.36, respectively), suggesting that cracking susceptibility may be minimized in cool weather and in light-textured soil. Irrigation management in the final 30 days preceding harvest had no consistent effect on root cracking. Time of day of harvest had a small but significant effect, with roots harvested before 0800 hr being more crack-susceptible. N fertilization in excess of that required to maximize root yield significantly increased cracking susceptibility. Cultivars varied widely in cracking susceptibility, with less variation in tissue strength and stiffness. Removal of the periderm dramatically decreased susceptibility to both cracking and breakage.
Cracking of carrot (Daucus carota L.) roots during harvest and handling is a serious problem for the commercial industry, particularly for `cut and peeled' products. Thirty commercial fields of cv. `Sugar Snax' in California were surveyed over the period 2000-03. Soil texture was determined, and soil and crop nutrient status, air temperature and soil moisture were monitored. In 10 fields the effect of excessive N fertilization was investigated; 90-180 kg·ha-1 N was sidedressed in addition to the growers' N regime. At one site a comparison of 10 cultivars was conducted to determine the root cracking sensitivity of commercial cultivars suitable for the cut and peeled market. In all fields roots were hand harvested, with undamaged roots 18-24 mm in diameter selected for study. Roots were cooled to 5 °C and subjected to an impact test to rate cracking sensitivity. Fields varied widely in root cracking sensitivity, with 4% to76% of roots cracked in the impact test. Cracking sensitivity was positively correlated with the % silt and clay in soil, and with air temperature in the final month of growth. Irrigation management had no consistent effect on cracking sensitivity. N application in excess of the growers' N regime did not increase carrot yield, but increased root cracking sensitivity by an average of 30%. Root cracking varied among cultivars from 10% to 49%. However, when the periderm was peeled from roots before impact testing, incidence of cracking declined to 2% or less in all cultivars. Periderm strength or flexibility is apparently the dominant factor in carrot cracking sensitivity, and environmental and management variables that affect cracking sensitivity must do so by affecting the periderm structure.
Two levels of natural sunlight attenuation and three levels of fertilizer were evaluated on five-year-old cocoa trees growing under field conditions. Sunlight effect was evaluated by comparing two densities of shade trees, Gliricidia sepium: 4×4 m and 8×4 m, allowing aproximately 25% and 50% of full sunlight (2000 μmol-2 s-1), respectively. The amount of soil-applied, fertilizer was 0 (control), 700, and 1000 g tree-1 year-1 17-17-17 (N-P-K) applied twice a year. Treatments were replicated 3 times in a split-plot design.Shade density of 8×4 m yielded the best dry cocoa bean production per ha. Production increased proportionally with the amount of fertilizer. We conclude that as the amount of light reaching tree canopy increases, the need for fertilizer also increases, and consequently yields improve. However, cocoa growers have to manage this characteristic carefully because tree life is diminished under more sunlight.
Eight-year-old cocoa trees growing under shade of different tree species were treated during three years with foliar and soil fertilizers and compared to non fertilized trees. We hypothesize that non fertilized trees under shade condition recycle their own nutrients by using fallen foliage from the shade trees and, in a fertile soil, they do not need addition of chemical fertilizers. Eight treatments, selected from growers' technology were evaluated under a randomized complete block design with 4 replications and 12 trees per experimental unit. Fertilized treatments did not differ from the non fertilized treatment in dry bean production and tree growth. This indicates that shaded cocoa plantations established in good fertile soils sustain their own nutrient requirements. The results also showed that foliar urea (1%) reduced cherelle wilt (yellowing and subsequent shriveling of young fruits).
Embryo abortion and empty seeds after self-pollination occur in some transgenic (ACO antisense) `Galia' male parental lines. An embryo-rescue system in this melon was developed to save potential viable embryos. To obtain the best and reliable embryo-rescue technique, several parameters were used including an improved (five new supplements) nutrient medium (named E-21) from the E-20A basic medium (Sauton and Dumax de Vaulx, 1987), an inoculation system (removing the embryo from the seed or intact seed), and the use of different fruit harvesting dates of the wild type and a transgenic `Galia' male parental line. Fruits of wild type (WT) and transgenic (ACO gene in antisense orientation) `Galia' male parental line were harvested at 4, 10, 17, 24, and 30 days after pollination (DAP). Fruits were surface sterilized by dipping in a 20% commercial bleach solution for 30 minutes. Subsequently, seeds were removed from fruit under sterile conditions. These seeds were either used to dissect the embryos or placed directly with the hilum facing E-20A or E-21 medium. Seedlings from all treatments were transferred to E-21 elongation medium, incubated 4 weeks, and transferred to soil to evaluate growth. The efficiency of this technique was greater when the time after pollination (4, 10, 17, 24, and 30 DAP) to rescue the embryos was increased. Thus, 30 DAP was the best time to rescue the embryos. The number of rescued embryos using E-21 medium was greater than with E-20A. We did not find any significant differences in survival efficiency rate between WT and transgenic embryos. We have obtained a competent embryo-rescue technique for WT and transgenic `Galia' male parental line, which can be applied to rescue valuable GMO hybrid-melon embryos.
Pollen germination timing has a paramount role in fertilization of a flower. Rapid germination and outgrowth of a pollen tube that penetrates the stigma is required. Physical and biological factors can affect pollen germination timing. The objective of this study was to determine if ACC oxidase antisense gene expression could influence in vitro pollen germination and in vitro pollen tube length growth. A transgenic (ACC oxidase antisense) `Galia' male parental line had a reduced fruit set compared to its wild type. Likewise, embryo abortion and empty seeds after self-pollination in a `Galia' male parental line were observed. Wild type and transgenic `Galia' male parental line melon plants were grown in a greenhouse according to the practices of Rodriguez (2003). Male flowers were collected from these plants between 10 to 12 am; pollen was obtained by dipping the anther in germination medium (10.25% sucrose, 0.031% calcium nitrate, 0.015% boric acid, 0.0075% KNO3, and 0.016% MgSO4) at 25 °C and analyzed immediately, either for total percentage of germination after 5 minutes of incubation or to measure pollen tube growth rate every 5 minutes during 1 hour. Each flower provided an average of 250 pollen grains. Assays were conducted by using the “Hanging Drop Method” (Okay and Ayfer, 1994). Percentage of pollen germination in WT `Galia' male parental line was greater than the transgenic line. Likewise, in vitro pollen tube growth in wild type `Galia' melon was greater than pollen from the transgenic line. Possibly the ACC oxidase antisense gene expression in `Galia' male parental line may have had an influence on the reduced fruit set observed.
Panicles of `Kohala' longan (Dimocarpus longan Lour.) trees often retain more than 250 fruit, which results in small fruit (<10 g) of reduced market value. During 1997 and 1998, we conducted experiments to increase fruit size in commercial groves. Trees flowered and fruited normally in 1997, but very scarcely and late in 1998. In 1997, treatments consisted of panicle pruning (clipping off half of the panicle) and/or removal of entire panicles (50% per tree) when young fruits were 5 or 10 mm in diameter. Control trees were left intact. The number of fruit per panicle varied greatly within trees. Panicles (pruned or intact) with <125 fruit generally developed fruit >15 g (32–33 mm equatorial diameter). Total soluble solid content of mature fruit generally decreased with increasing fruit size. Removing whole panicles did not increase average fruit size in remaining intact panicles, suggesting that panicles were fed primarily by leaves within the same branch. In 1998, treatments consisted of applications of GA3 and/or CPPU (a synthetic cytokinin) when fruits were 6 to 9 mm in diameter. Panicles were not pruned since they generally had <150 fruit. Control panicles were not sprayed. There was no consistent effect of treatments on average fruit weight, and no treatment significantly increased fruit size in relation to controls. These preliminary results indicate that other factors besides current fruit set, such as previous fruit load of a branch, branch position (exposure to sunlight and/or wind, and proximity to major limbs), and the amount/age of leaves, may influence the fruiting potential of individual branches.
Fruit soluble solids concentration (SSC) is an important quality factor for tomatoes (Lycopersicon esculentum Mill.) grown for processing. The use of drip irrigation often results in undesirably low SSC. The effects of late-season irrigation management on fruit yield and SSC was investigated in a series of drip-irrigated field trials in California from 2000–04. The effects of irrigation cutoff or deficit irrigation implemented 40 to 50 days preharvest (the period corresponding to the initiation of fruit ripening) were compared to a standard grower practice of irrigation cutoff 20 days preharvest. Irrigation cutoff 40 to 50 days preharvest increased SSC but resulted in substantial yield loss, with significantly reduced brix yield (Mg fruit solids ha-1). By contrast, deficit irrigation significantly increased SSC compared to the standard practice, with no significant loss of brix yield. In three commercial fields the effect of deficit irrigation on fruit SSC was investigated. Fruits were sampled on three dates: 1) 4 to 5 weeks preharvest, early-ripening, pink-stage fruit only, 2) about 1 week preharvest, both late-ripening, pink-stage fruit and early-ripening fruit now fully ripe, and 3) commercial harvest, composite of early- and late-maturing fruit. SSC increased in response to soil moisture stress induced by deficit irrigation, with late-maturing fruit as much as 1.6 °brix higher than fruit maturing before significant soil moisture stress. However, once a fruit reached the pink stage of maturity, its SSC was not affected by subsequent soil moisture stress. An additional five commercial field trials were conducted to compare growers' irrigation practices with greater degrees of deficit irrigation. In each field the grower's deficit irrigation regime was compared to a reduced treatment receiving 25% to 50% less water over the final 4 to 7 weeks before harvest. Across fields, applying 20% to 60% of reference evapotranspiration (ETo) over the fruit ripening period resulted in acceptable SSC without significant brix yield reduction. We conclude that deficit irrigation initiated during early fruit ripening provides a flexible tool for SSC management. Brix monitoring of earliest ripening fruit can help classify fields as to the severity of irrigation deficit required to reach desirable SSC at harvest.
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.
Soluble solids concentration (SSC) is a major quality factor for tomatoes (Lycopersicon esculentum Mill.) grown for processing. The effects of early irrigation cutback were investigated in a series of drip-irrigated field trials in California from 2000-03. Irrigation cutback was initiated from 4-7 weeks preharvest, with irrigation volume reduced to 30% to 70% of reference evapotranspiration. Early irrigation cutback was compared to full irrigation until cutoff 2-3 weeks preharvest. SSC was monitored from the initiation of deficit irrigation until harvest, with breaker-stage fruit sampled at approximately 10-day intervals; additionally, early-maturing fruits were tagged on the plant at breaker stage and retrieved at harvest for SSC analysis. Fruit yield, overall SSC, and brix yield (Mg·ha-1 fruit solids) were evaluated at commercial maturity. Fruit SSC increased in response to soil moisture stress, with late-maturing fruit as much as 2.0 °Brix higher than fruit maturing before significant moisture stress. However, once a fruit reached the breaker stage of maturity, its SSC did not increase regardless of subsequent soil moisture stress. Across field trials, yield decline resulting from early irrigation cutback was matched by a corresponding increase in overall SSC, resulting in equivalent brix yield in all test fields. We conclude that the early irrigation cutback provides a flexible tool for SSC management and that °Brix monitoring of breaker-stage fruit can augment soil moisture monitoring to tune irrigation management to field-specific conditions.