STUDY OF BIOCHEMICAL AND MOLECULAR MECHANISMS INVOLVED IN THE REGULATION OF RIPENING IN THE CLIMACTERIC PEACH (PRUNUS PERSICA L. BATSCH) FRUIT
Tesi di Dottorato
Data di Pubblicazione:
2010
Citazione:
STUDY OF BIOCHEMICAL AND MOLECULAR MECHANISMS INVOLVED IN THE REGULATION OF RIPENING IN THE CLIMACTERIC PEACH (PRUNUS PERSICA L. BATSCH) FRUIT / F. Baldin ; Tutor: Maurizio Cocucci ; Co-tutor: Noemi Negrini, Silvia Morgutti ; Coordinatore: Daniele Bassi. Università degli Studi di Milano, 2010 Dec 16. 23. ciclo, Anno Accademico 2010. [10.13130/baldin-federica_phd2010-12-16].
Abstract:
Abstract
Peach (Prunus persica[L.] Batsch) is temperate fruit species of economic importance, it ranks second in fruit production in Europe after apple. Peach fruit are classified by different flesh firmness, which strongly influences fruit shelf-life and storage, and ethylene evolution, which determinates the organoleptic quality of the ripening fruit.
Concerning flesh texture, three main distinct peach fruit phenotypes are known, even if not all is understood in terms of their genetic determination and differences in biochemical pathways activated during the final stages of ripening which lead to the definition of phenotypic-specific characteristics. The first two phenotypes, described by Bailey and French, 1932, are the melting (M) and non-melting (NM) flesh. The M texture shows a prominent softening in the final stage of ripening. Variability of firmness is found within this phenotype and Yoshida (1976) distinguished between soft, medium and firm. The NM phenotype (the so called ‘canning peach’) shows a firm texture when fully ripe that never becomes soft. Rather, it becomes rubbery (for the loss of water from the tissues) during the senescence stage, when most cultivars could also display the development of peculiar off-flavours (Sherman et al., 1990). The third flesh texture phenotype was described by Yoshida (1976). He firstly classified a very firm and crispy, ‘stony hard’ (SH) flesh phenotype as belonging to the M family. However, these fruit never soften and resemble a NM phenotype, becoming rubbery when senescent. A possible fourth flesh texture trait resembles very much the SH flesh in firmness and crispiness, but when fully ripe becomes melting. This flesh texture is found in many recently developed new cultivars (nectarines, as ‘Big Top’, and standard peaches, e.g. ‘Rich Lady’ and ‘Diamond Princess’; Monet and Bassi, 2008).
Availability of newly established peach cultivars with optimal organoleptic (as for M phenotypes) and durability [as for NM, SH and Slow Melting (‘Big Top’) phenotypes] characteristics would represent an economic advantage improving shelf-life and economic value of the produce. To do this, and in order to plan proper breeding programmes, a possible strategy may consist in the identification of molecular markers linked to the “flesh texture” phenotype.
In this work, particular attention has been devoted to the development of different characteristics of flesh texture as a function of the structure of the endo-PG gene and of fruit ethylene evolution and response. The research work was articulated in four main topics:
1. Chapter I reports the results of some physiological, biochemical and molecular aspects of the Melting of the ‘Big Top’ Nectarine Fruit. We have characterized the postharvest behavior of ‘Big Top’ fruit, treated or not with ethylene for five days after harvest (DAH), and compared it with that of ‘193 Q XXVII 111’, a SH peach selection (‘Ghiaccio’), and with that of an accession with very firm flesh, ‘D41-62’. Pp-ACS1 expression, ethylene evolution, endo-PG production and softening characteristics have been evaluated in fruit of the three genotypes and referred to those of ripe melting flesh (M) ‘Bolero’ at harvest. Like ‘Bolero’, ‘Big Top’ fruit did express Pp-ACS1 and evolve ethylene, but with a 5-d delay during postharvest. Pp-endo-PG expression, production of an active endo-PG isoform typical of ripe peach fruits and fruit melting showed a parallel behavior; ethylene treatment further enhanced all the above features. In SH ‘Ghiaccio’ Pp-ACS1 expression, ethylene evolution, endo-PG production and softening were virtually absent during the first five DAH in air. ‘Ghiaccio’ neither expressed Pp-ACS1 nor evolv
Tipologia IRIS:
Tesi di dottorato
Keywords:
Pp-EndoPG ; ripening ; flesh texture ; peach ; Prunus persica
Elenco autori:
F. Baldin
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