Quality fruit

Weibel, F P, Bickel, R, Leuthold, S and Alfoldi, T (2000) Are organically grown apple tastier and healthier A comparative field study using conventional and alternative methods to measure fruit quality , in Acta Horticulturae, 517, 417-427. 

Reasons for varying fruit quality interactions between site conditions and management factors... 

The choice of rootstocks was until recently thought to primarily affect the growth and vigour of the tree and to only have a minor effect on intrinsic fruit quality. However, recent research has shown that, under low input organic production practice, the choice of rootstock can have a significant influence on tree fitness and tree nutrient acquisition, and thereby also on fruit quality (Weibel et al., 2006a). 

To achieve a good intrinsic visible fruit quality, biotic and abiotic stress to the trees has to be controlled. Therefore, conventional fruit orchards are often fitted with relatively expensive installations such as wind break hedges, hail nets, irrigation systems and wind machines for frost prevention, irrigation and liquid fertilisation facilities and wild animal fences. Apart from liquid fertilisation systems, most of these installations can also be installed in organic orchards and help to assure yield and quality security. 

Most dynamic factors that affect fruit quality are agronomic practices that can be changed by farmers over relatively short time spans. They are mainly related to fertility management and crop protection and other husbandry interventions and inputs such as pesticides, fertilisers, herbicides, thinning agents and so on. The permitted tools for these activities, however, differ greatly between conventional and organic fruit production. The consequences... 

In comparative studies of organic and conventional fruit quality it is important that the fruit samples compared originate from trees with an optimum or equivalent fruit load (e.g. see Weibel et al., 2000), to avoid the confounding effects of fruit load on quality. Unfortunately, in most comparative studies on fruit quality this factor was not addressed (Bourn and Prescott, 2002 Harker, 2004). 

The level of plant mineral nutrients available to trees is known to affect fruit quality, but its relative effect is often overestimated compared to other factors such as fruit load and light (and associated assimilate supply to fruit) (see sections above) (for review see Neilsen and Neilsen, 2003). The mineral nutrition of trees and fruits is complex. Uptake of the macronutrients nitrogen... 

Fig. 16.2 A 3-year on-farm comparison study in Switzerland where microbial activity in orchard soils (expressed as the ratio of microbial bound carbonmitrogen) was higher (low values indicate higher bacterial presence and activity) in organic (filled symbols) than in integrated (open symbols) managed orchards (same symbol shape = orchards in the same village), (a) A clear correlation between the Cmic Nmic ratio to phosphorus content of the fruit flesh was found which (b) in turn was correlated with the fruit quality index (including sugar and acidity content and fruit flesh firmness) P = phosphorus content of the fruit fresh in mg/kg dry matter.

These results clearly indicate that fruit growers should not lower fertility inputs below the level required for satisfactory tree performance and intrinsic fruit quality, and also content of polyphenols. Thus, balanced nutrition without over or under supply of nutrients should be targeted in organic fruit production. 

Weed competition for water and nutrients can have similar effects on fruit quality as described above for fertilisation. For example, if weed competition is completely prevented by chemosynthetic herbicides in conventional production, this can lead to excess supply of certain mineral nutrients, in particular nitrogen and potassium, which in turn results in reduced sensory quality and shelf-life (Section 16.2.2). On the other hand, excessive weed competition, in particular, during the pre-bloom phase and the end of the first shoot growth period (Gut and Weibel, 2005), can induce nutrient and/or water deficiency and a risk of quality loss. 

As a result, organic fruit growers have to make maximum use of preventative or indirect plant protection measures, some of which were already described in terms of their effect on fruit quality (e.g. lower planting densities, see sections above). However, there remains an increased risk for pests and diseases causing stress, decreased photosynthetic activity and capacity. Also in certain sensitive cultivars, the application of permitted plant protection products (such as lime sulphur) can result in phytotoxic effects or latent stress in trees (Palmer et al, 2002). The decrease in photosynthetic activity by both pest/disease attack and pesticides may, in turn, result in reduced fruit quality. Both long-term latent and short-term acute side effects of organic plant protection products have not yet been sufficiently investigated. 

Table 16.3 Standard fruit quality parameters measured at the beginning (December) and towards the end (February) of storage period over three years. Means are of five organic orchards (bio, upper figure) and five conventional orchards (IP, lower figure) working to integrated farming standards ( = P < 0.05)...

Fig. 16.7 Correlations between the vitality quality index (based on data from picture forming methods and the index of technical quality (based on classical fruit quality tests, see text) in the first year (left) and the second year (right) of the study (filled symbols = organic, open symbols = conventional same symbol form = same village).

In this chapter we have explained several system-inherent factors of organic fruit growing that can improve fruit quality. However, with the intensification of organic fruit production currently under way worldwide (e.g. more intensive nitrogen application on horticultural crops), there is a risk of quality decrease. Therefore, technical progress in organic farming should be closely and scientifically monitored for (side) effects on food quality, possibly in a holistic view that also includes environmental, social and human health criteria. 

Palmer, J.W., S.B., D., Shaw, P. and Wunsche, J.N. (2002). Growth and fruit quality of Braeburn apple (Malus domestica) trees as influenced by fungicide programmes suitable for organic production , New Zealand Journal of Crop and Horticultural Science, 31, 169-177. 

Dorais M, Papadopoulos AP and Gosselin A. 2001a. Greenhouse tomato fruit quality. Hort Rev 26 239-319. 

Rapisarda P, Bellomo SE and Intelisano S. 2001. Storage temperature effects on blood orange fruit quality. 

Watercore in durian is usually associated with a bitter taste and unacceptable fruit quality so the ability of MRI to detect this condition is significant. The watercore disorder shows up as a bright region of increased free water near the central core of the fruit " not a dissimilar observation to that of Wang and co-workers with watercore in apples. 

S. Pathaveerat, M. J. McCarthy and P. Chen, Abstracts of the Potsdam Symposium on Fruit Quality, ATB, Potsdam, 2001. 

Cultivated plums can be sweet, melting dessert fruits or tangy, firm cooking fruits, in shades from yellow to blue to nearly black. In all but the most extreme climates, there is a plum tree for every yard. Wild American plums grow in Zones 4-8, European and damson plums thrive in Zones 5-9, and Japanese plums do best in Zones 6-10. Hybrids between American and Japanese plums combine the cold hardiness of the former with the fruit quality of the latter. 

The three key fruit quality traits, color, heat, and flavor, are independent characteristics. The color of a fruit does not predict the hotness, despite many consumers associating green peppers with no-heat bell peppers and red powder with hot cayenne chile. Hence in New Mexico, the state question is Red or Green to determine which version of the host s salsa or enchilada is hotter. From a phytochemical perspective the independence of these traits relates to the biosynthetic pathways for these compounds and the genes for both the structural and regulatory genes for those pathways. This review describes some of the recent advances in the analyses of the compounds, enzymes, and genes associated with color and flavor in Capsicum. 

Shorrocks, V.M. and D.D. Nicholson. 1980. The influence of boron deficiency on fruit quality. Acta Hortic. 92 103-108. 

PGR potential has been limited largely to root inducing-chemicals and applications to control fruit quality. 

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