Acidity and sweetness in apple and pear

Abstract

Sweetness and acidity in apple and pear inherit independently and can be organoleptically evaluated separately, but less accurately in pear than in apple . For breeding purposes an analysis of fruits for acidity and sweetness with pH indicator paper and a hand refractometer is to be prefered to the organoleptic method .In apple, the acidity -decreasing with time -of the unripe fruit was already strongly indicative of that of the eating-ripe fruit ; sugar -increasing with time -not before the fruit was picking ripe . Sugar content in apple and pear, and the pH in pear, appeared to be normally distributed ; the pH in apple showed a segregation into an acid and a low-acid group, which occurred in both the unripe and ripe stage . The segregation ratio between these groups was found to be highly variable . On the whole, the mean acidity and sugar content of apple and pear progenies is significantly determined by that of the parents . Most of the observations made did not support the theory that low acidity in apple is determined by one recessive gene . The relationship between the pH of leaf juice and fruit juice in apple may offer a possibility for pre-selection .

Genetic characterization of the Ma locus with pH and titratable acidity in apple

“…Based on these data, it appeared to be sufficient to simply evaluate fruit pH using pH papers to screen large populations in genetic studies of Ma that only need to discriminate the lowacidity genotypes (pH [ 3.8) from the high/medium group. Discovery and genetic mapping of the Ma locus were largely accomplished by estimation of fruit pH with pH indicators (Nybom 1959;Visser et al 1968;Visser and Verhaegh 1978;Maliepaard et al 1998). However, for selection and breeding purposes, TA also should be determined in order to more comprehensively evaluate acid and taste, including its derivative, the fruit sugar to acid ratio.…”

“…As there is a relatively wide acidity spectrum in highand medium-acid fruits, the dominance of high and medium acidity over low acidity was considered to be quantitative (Brown and Harvey 1971). This additional variation within the dominance class is proposed to be explained by the additive gene action model (Visser et al 1968;Visser and Verhaegh 1978).…”

Determination of sugar and acid content in apple

“…In order to be able to compose a representative sample for analysis, several factors have to be taken into account. Of particular importance is the stage of maturity of the fruit (see VIssER et al ., 1968) . Furthermore, the position of the fruit on the tree (north, east, south or west side) has an effect, while there are also small differences in sugar content between the exposed and shaded sides of the fruit .…”

“…In the orchard a rapid evaluation of sugar and acid contents is possible by determining the refraction with a hand refractometer in the pressed juice of one fruit (chosen by an expert) and the pH with indicator paper (see VISSER et al, 1968) . The advantage of using pH indicator paper is that it evaluates acidity quantitatively, while the bromocresol green method, also used by NYBOM (1959), only divides the fruits into two groups ('acid' and `sweet') .…”

Inheritance of Chemical Constituents of Apple Fruit and Leaf in Two Sets of Diallel Crosses

“…Nybom (1959) and Brown and Harvey (1971) published genetic studies indicating the simple inheritance of acidity in apple, and on a quantitative pattern found by the latter and by Visser et al (1968) for sweetness. Spangelo et al (1956), breeding apples for resistance to scab, reported data supporting the findings of Hough et al (1953) Watkins and Spangelo (1970).…”