Euphytica DOI 10.1007/s10681-011-0572-1 Influence of year and genetic factors on chilling injury susceptibility in peach (Prunus persica (L.) Batsch) Pedro J. Martı´nez-Garcı´a • Cameron P. Peace • Dan E. Parfitt • Ebenezer A. Ogundiwin • Jonathan Fresnedo-Ramı´rez • Abhaya M. Dandekar • Thomas M. Gradziel • Carlos H. Crisosto Received: 30 August 2011 / Accepted: 29 October 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Chilling injury (CI) is a major physiolog- susceptibility factors and/or experiences inducing ical problem limiting consumption and export of peach conditions. The F-M locus also greatly influences and nectarine (Prunus persica (L.) Batsch). To clarify susceptibility to flesh bleeding, although the physio- the genetic basis for chilling injury, inheritance of the logical mechanism for this disorder is unclear and may major CI symptoms mealiness, flesh browning, flesh be controlled by a different gene closely linked to bleeding, and flesh leatheriness were examined over endoPG. Unlike mealiness, flesh bleeding occurred three years in two related peach progenies. In addition, primarily in non-melting flesh fruit, particularly when genetic relationships among traits and the year-to-year the fruit is white-fleshed. Flesh browning incidence variation in trait performance in these progenies were was greater in mealy fruit and was not associated with tracked. Both populations also segregated for Free- flesh bleeding. Breeding for CI resistance is thus a stone-Melting flesh (F-M) and yellow flesh. There viable long-term strategy to reduce losses in the fresh were significant differences in CI symptoms among and processed peach and nectarine industries. This years. The major gene endoPG, which controls the study is an important first step to understanding genetic F-M locus, provides resistance to mealiness in non- control of CI symptoms in peach. melting flesh fruit. Only fruit with melting flesh can develop mealiness if the tree possesses other genetic Keywords Breeding strategy Á Chilling injury Á Flesh bleeding Á Flesh browning Á Genetic factor Á Heritability Á Leatheriness Á Mealiness Pedro J. Martı´nez-Garcı´a and Cameron P. Peace contributed equally to the preparation of this paper. Introduction P. J. Martı´nez-Garcı´a(&) Á D. E. Parfitt Á J. Fresnedo-Ramı´rez Á A. M. Dandekar Á T. M. Gradziel Á C. H. Crisosto Many peach (Prunus persica (L.) Batsch) accessions Department of Plant Sciences, University of California, can develop a physiological disorder called chilling Davis, One Shields Ave, Davis, CA 95616, USA injury (CI) or internal breakdown (IB). This disorder, e-mail: [email protected] triggered by exposure to cold storage temperatures, C. P. Peace affects several organoleptic attributes such as texture, Department of Horticulture and Landscape Architecture, flesh color, and juiciness (Anderson 1979;Harding Washington State University, Pullman, WA 99164, USA and Haller 1934; Hartmann 1985;Smith1934; E. A. Ogundiwin Vonmollendorff and Devilliers 1988). The presence of Nunhems USA, Inc, Davis, CA 95618, USA chilling injury is a frequent source of complaints by 123 Euphytica consumers and wholesalers of peach (Crisosto et al. injury (flavor loss) rather than later aspects such as FB 1999). Externally, fruits with chilling injury appear development. sound, so the problem is usually not noticed until the Several treatments have been attempted as a short- fruit reaches retailers and consumers (Crisosto et al. term solution. Controlled atmosphere (Anderson 1999). A high frequency of affected fruit reduces 1979; Crisosto et al. 2009; Zhou et al. 2001), warming consumer satisfaction, limits development of long exposures (Anderson 1979; Lill 1985; O’Reilly 1947; distance markets, and reduces peach consumption. Zhou et al. 2001), and preconditioning (Crisosto et al. The major symptoms of CI are flesh mealiness (M), 2004; Guelfat-Reich and Ben Arie 1966) have been flesh leatheriness (FL), flesh browning (FB), flesh used commercially to mitigate CI in peach fruit (Lurie bleeding (FBL), loss of flavor, and development of and Crisosto 2005). Among these treatments, precon- off-flavors (Crisosto et al. 1999). Mealiness (M) is a fruit ditioning is widely used commercially and, when flesh textural disorder, where affected ripe fruit have a properly applied, delays CI symptom expression for dry, grainy feel when chewed. In simple terms, mealy 10 to 12 days, enough to improve the quality of some fruit are dry and soft when ripe, while leathery fruit are peach cultivars on arrival (Crisosto et al. 2009; either dry and firm when ripe or remain firm because of a Crisosto and Valero 2008). Unfortunately, the benefits failure to ripen (Luza et al. 1992;Juetal.2000). of these treatments have been erratic, and when Desirable, non-mealy fruit are juicy with a soft, melting postharvest life has been extended, the time of texture, or are juicy and firm (Crisosto et al. 1999). extension has been too short to have a commercial On a cellular level, metabolism of the pectin impact. An early review of orchard factors affecting component of the cell wall is altered in mealy fruit. A peach CI such as nitrogen fertilization, deficit irriga- gel is formed as pectins in intercellular spaces absorb tion regimes, maturity, canopy position, crop load, free water, intercellular adhesion is reduced, and cells fruit size, environmental conditions, season, and form loose clumps rather than rupturing to release juice genotypes concluded that genotype was the most (Brummell et al. 2004). Flesh browning (FB) is often important factor among them (Crisosto et al. 1997). In seen in mealy fruit, although it can also occur in the general, clingstone nectarine cultivars were less absence of mealiness (Crisosto et al. 1999; Brummell susceptible to CI than peach cultivars (Crisosto et al. et al. 2004). Flesh browning (FB) occurs when 1999; Brovelli et al. 1998) and non-melting flesh enzymes such as polyphenol oxidase act on phenolic cultivars have reduced endoPG activity and less CI substrates with which they come in contact (Kader than melting flesh cultivars (Lester et al. 1996). et al. 1984). Flesh bleeding (FBL) is caused by the The variation in CI susceptibility among commer- movement of water-soluble red pigments, probably cial cultivars and selections when stored at either 0 or anthocyanins, through the fruit flesh during cold 5°C (Crisosto et al. 2008, 1999; Mitchell 1987; Cantin storage or after subsequent ripening (Lurie and et al. 2010) indicated that CI is genetically controlled. Crisosto 2005). It can be present at harvest or develop Clingstone non-melting flesh (CNMF) peaches, which as fruit ripen and senesce on the tree. The progression are primarily used in canning but are also popular in of M and FB symptoms is associated with reduced the European and South African fresh markets, are perception of normal flavor and with development of largely free of CI, although the physiological basis for off-flavors (Crisosto 2002; Crisosto et al. 1999). this resistance has not been addressed (Brovelli et al. In most cultivars tested, flavor loss (‘‘hidden 1998; Crisosto et al. 1999). Melting flesh (MF) damage’’) is perceived prior to lack of juice or cultivars vary in susceptibility to CI, with some mealiness, and FB is generally the last visual symptom varieties exhibiting symptoms in all fruit after only of CI damage to develop (Crisosto and Labavitch one week of cold storage even at 0°C, while others 2002; Infante et al. 2009). The documented sensory appear resistant, withstanding six weeks of cold damage underscores the effect of CI complex damage storage before eventually ripening and senescing on consumer preference and fruit consumption, and (Crisosto et al. 1999). To provide a long-term solution thus, its commercial importance. In addition, more to CI, genetic resistance to this disorder is desirable for attention should be focused on obtaining cultivars with new MF peaches destined for the fresh market. This genetic tolerance/resistance or in developing posthar- may be achievable by phenotypic selection for resis- vest innovations to control early stages of chilling tance in breeding program progeny. However, the 123 Euphytica inheritance of symptoms has not been quantified, and Trait evaluation strategies for genetic improvement through breeding would be greatly aided by knowledge of the underly- Each parent and each individual genetic progeny were ing mechanisms of genetic control. monitored for three successive years. Fifteen sound The genetic basis for chilling injury has not been fruits per tree were harvested at commercial maturity described in stone fruits. The inheritance of the major and immediately taken to the postharvest evaluation CI symptoms M, FB, FBL, FL, and the phenotypic laboratory. Each fruit was treated with a fungicide dip, correlations between those symptoms, are described 1.2 g l-1 of iprodione, cold-stored under CI-inducing here using two related peach progenies. In addition, condition (5°C for two weeks), and then ripened at year effect was determined for the same symptoms. room temperature to assess CI symptom expression. The CI symptoms mealiness (M), flesh browning (FB), flesh bleeding (FBL) and flesh leatheriness (FL) were Materials and methods evaluated (details below). Each tree was classified as producing fruit that were either freestone or cling- Plant material stone, melting or non-melting flesh, and white or yellow flesh. Two peach progenies segregating for CI symptoms After two weeks storage, fruit exhibiting fungal were used in this study. The first, Pop-DG, was decay caused by brown rot (Monilinia fructicola) were composed of 70 F1 seedlings from a cross between removed. Sound fruit were sectioned into two halves the commercial cultivars ‘Dr. Davis’ and ‘Georgia and CI symptom severity determined. M and FL were Belle’. ‘Dr. Davis’ produces yellow, clingstone, non- assessed as described (Crisosto et al. 1999) and their melting flesh (NMF) fruit and is a major cultivar grown presence or absence in each fruit was recorded.