Medium- to large-size fruit are preferred and are the most profitable. For example, apple cultivars that have the majority of fruit in the 7 to 8 centimeter size category are favored in the marketplace (Hampson and Quamme, 2000). Cultivars that are genetically inclined to produce fruit in the smaller size categories are less profitable, since additional expense will be required to adjust culture to produce larger fruit. Fruit can be too large, however. Cultural adjustments to reduce size on large-fruited cultivars add expense and may reduce quality and increase the possibility of biennial bearing.
32 CONCISE ENCYCLOPEDIA OF TEMPERATE TREE FRUIT Appearance
The initial selection of a pome or stone fruit for further evaluation is usually due to attractive appearance. Color is a principle attribute. Apples that have a clear, glossy yellow or a bright red or green color will have an advantage. Peaches are preferred that have a bright red blush over a large portion of the surface. Cherries with a deep red color are generally more desirable. Fruit shape is another consideration. Generally, an apple with a moderate to high length to diameter (L/D) ratio is preferred to a very flat fruit. A round peach is usually more desirable than an oblong or very flat one. Surface blemishes, such as russet or scarf-skin on apples, detract from appearance and customer appeal.
Flavor is emerging as being the most important attribute that a fruit must have to become commercially successful. Aroma and complex flavors are favored and sought after by many consumers. A recent survey of customers in three major cities in the United States reveals that over 90 percent of consumers consider taste to be the most important factor when making apple purchasing decisions (Ricks, Heinze, and Beggs, 1995). Consumers have become accustomed to having a number of alternative flavors available in the produce section, and a fruit that lacks the flavor component will not sell and will not be commercially viable for growers to plant.
Flavor has two aspects: sweet/tart ratio and aromatics. Distinct preferences exist among people. These differences can manifest themselves as national, regional, or local preferences. Fruit that are predominately sweet and have relatively low acids are favored by Asian populations in the Pacific Rim area. Apple cultivars such as 'Fuji' or 'Tsugaru' are preferred and grown in that region. Individuals who live in northern Europe generally prefer fruit that are more tart and have higher acid levels. Apples grown there include 'Jonagold', 'Cox's Orange Pippin', and 'Elstar'. New peach cultivars offer consumers more flavor choices than in the past. Some of the recent selections have low acid contents. The majority of consumers in the world favor an appropriate balance between sweet and tart.
Identification of eating quality of fruit using analytical methods such as firmness, soluble solids, or titrateable acidity is relatively un reliable and therefore of limited use in a screening process (Watada etal., 1981). Increasingly, sensory evaluation offruit is being used as a method to identify and select promising new cultivars. Taste panels have proven to be quite reliable predictors of preferences consumers have for different cultivars and strains of cultivars.
Texture, Firmness, and Juiciness
Texture, firmness, and juiciness are attributes that are intimately associated with, but distinctly different from, flavor. Barritt (2001) suggests that crispness is the most sought after trait with apples. Flesh should literally crack, and upon chewing, the apple should melt and disappear quickly. Ricks, Heinze, and Beggs (1995) also report that crispness is a key factor consumers identify as being important in making apple purchase decisions. Peaches are preferred that have smooth, melting flesh. Cherries should be crisp yet mellow. Associated with texture is juiciness. This is a highly sought after trait that is equated with freshness. A fruit must be firm, but, above all, it must be juicy and crisp or melting to be appealing enough to purchase in preference to other cultivars or produce. These attributes must remain relatively unchanged for a number of days after the consumer takes the fruit home.
A new cultivar must have characteristics that will allow the grower to make a fair profit. It should have attributes that will allow high annual yields with substantial percentage packouts in the highest fruit grades. Some favorable cultural characteristics include annual flowering, ease of thinning, high productivity, absence of physiological problems or nutrient disorders, and desirable tree growth.
Bruising is one of the most common reasons that temperate fruit are downgraded or culled. Cultivars that do not bruise easily are preferred. Customers consistently select pome or stone fruit that maintain firmness and texture for an extended period of time and are not subject to storage disorders. Therefore, handling and storage characteristics are important criteria used to identify exceptional selections.
34 CONCISE ENCYCLOPEDIA OF TEMPERATE TREE FRUIT Disease Resistance
Tree fruit traditionally have required many sprays to produce commercial, blemish-free crops. Many of these sprays are applied to control diseases. Resistance to the most common and devastating diseases can be found in a number of apple cultivars. Apple scab (Venturia inaequalis) is the most serious disease of apples worldwide. Popular cultivars such as 'Liberty', 'Enterprise', and 'Gold Rush' are scab resistant. Bacterial spot is considered a serious disease on peaches, and its control requires multiple fungicide sprays. Peach and nectarine cultivars are selected for reduced susceptibility to this disease.
In areas that have severe winters, production is limited by winter injury or even death of trees. Cultivar selection is based on the ability of trees not only to withstand extremely cold temperatures but also to survive under fluctuating temperature conditions. The newly introduced apple cultivars from the University of Minnesota, 'Honey-crisp' and 'Zestar', illustrate that selection for cold hardiness does not necessarily come at the expense of selection for high quality. 'Madison', 'Harcrest', and 'Canadian Harmony' are examples of peaches that were selected for both quality and winter hardiness.
Production of temperate fruit in warm, subtropical areas is limited because most of the cultivars available require too many hours of chilling. In areas where production is limited due to low chilling, early leafing is a screening condition used to identify selections that may grow with little or no chilling.
Selection criteria vary by region, based on local conditions. For example, a grower-sanctioned program in Ohio selects mainly for lateness in bloom, a trait that may help avoid spring frosts prevalent in that area. Other selection and evaluation factors include flesh color, flesh oxidation, tree growth habit, tree vigor, and season of ripening.
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