Melon fresh fruit quality from field to fork: a quality-oriented breeding and multivariate perspective

En Varsovia, invitado por la organización de este congreso sobre nuestras investigaciones en melón este mes de Septiembre dentro de los proyectos financiados por el Ministerio de Economía e Innovación y los fondos regionales EU-FEDER y la Fundación Séneca de la Región de Murcia. La conferencia claro es en inglés, pero podéis aprovechar las herramientas de Google Translator.

Esta es la referencia del congreso que os menciono:

Fernández-Trujillo, J.P. Dos-Santos, N., Bueso, M.C. Esteva, J., Martínez, J.A., Monforte, A.J. 2013. Melon fresh fruit quality from field to fork: A quality-oriented breeding and multivariate perspective. En: Quality of fresh produce, herbs and vegetables – from field to fork; September 18-19, 2013. Warsaw University of Life Sciences – SGGW. Warsaw, Poland. Conferencia invitada. Book of abstracts p.39-40.  

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A conference entitled: "Melon fresh fruit quality from field to fork: A quality-oriented breeding and multivariate perspective" was delivered on Thursday 19 September in a international mini-Workshop entitled "Quality of fresh produce, herbs and vegetables – from field to fork" organized in Warsaw (Poland) by Prof. Marek Gjewski, the lider of the Pakeltu Horticulture Warsaw Plant Heatlh Initiative during September 18-19. Warsaw University of Life Sciences – SGGW. Warsaw, Poland. I was invited to participate in this mini-workshop together with other colleagues from different part of Europe. This is the  link of the content of the mini-workshop..

http://f2f.woiak.sggw.pl/index.php?option=com_content&view=category&layout=blog&id=59&Itemid=148&lang=en

And this is a copy of the book of abstracts.

Melon fresh fruit quality from field to fork: A quality-oriented breeding and multivariate perspective

JUAN PABLO FERNÁNDEZ TRUJILLO^1,*, NOELIA DOS-SANTOS¹, MARíA C. BUESO², JUAN ESTEVA³, juan antonio martínez³, ANTONIO J. MONFORTE⁴

¹ Department of Agricultural and Food Engineering. Technical University of Cartagena (UPCT). Paseo Alfonso XIII, 48. ETSIA and Institute of Plant Biotechnology. E-30203 Cartagena (Murcia), Spain.

² Department of Applied Mathematics and Statistics. UPCT. Campus Muralla del Mar, Doctor Fleming s/n. ETSII. E-30202 Cartagena (Murcia), Spain.

³ Department of Plant Production. UPCT. Paseo Alfonso XIII, 48. ETSIA and Institute of Plant Biotechnology. 30203 Cartagena (Murcia), Spain

⁴ Instituto de Biología Molecular y Celular de Plantas (IBMCP). CSIC/UPV. Ciudad Politécnica de la Innovación - Edificio 8E Ingeniero Fausto Elio s/n,  46022 Valencia, Spain.

* e-mail: juanp.fdez@upct.es

Melon quality is a multivariate character with critical importance for melon consumers. Quality of horticultural crops can be measured instrumentally qualitatively or quantitatively but the sensory perception is the key trait for consumers. Fruit properties measured instrumentally may help us to verify proper fruit quality depending on the link of the postharvest chain involved. This conference summarizes results particularly from a quality-oriented breeding perspective that could contribute to improve or keep melon fruit quality. Examples of identification of quantitative trait loci (QTLs) associated with pre and postharvest factors affecting final fruit quality are reported.

            Preharvest factors and/or postharvest manipulation (storage, transport) may induce several fruit disorders as melon cracking that we have reviewed recently. A combination of different preharvest and postharvest factors contributes to the development of this disorder. In greenhouse production, environmental effects can be minimized but in open-field production uncontrolled factors as excessive rain and sun exposure together with inappropriate fertigation and lack of preharvest treatments contribute to a sudden development of the disorder as soon as two weeks before harvest and during the harvest season. Inadequate harvest and postharvest practices and genetic factors have also been identified as critical with some commercial cultivars, accessions and near-isogenic lines (NILs) of melon more prone to suffer cracking than others. Particularly QTLs associated with climacteric ripening or non-climacteric ripening have been identified for example in chromosomes III, VI and X of melon.

            Another set of critical quality traits  for consumer choices  most of them having an important genetic component apart from environmental or environmental x genetic components are morphological traits (fruit size and shape), aspect, netting, sutures, spots, fruit color, aroma, texture, and nutrient content (sugars, organic acids and amino acids, carotenoids, vitamins, etc.). Other complex traits of interest are for example the potentiality of the cultivar for fresh-cut product or the expected shelf-life, or improved resistance to physiological disorders (mealiness, chilling injury during storage, etc.), weight loss or decay. Successful attempts to modify some characters associated with physical traits are in progress, whereas the manipulation of external fruit characteristics as perfect round-shape and reduced size, netted melons instead of non-netted ones, etc. is currently feasible by selecting QTLs mapped during the last 10 years and of the relatively high heritability of these characters.

            Melon aroma is a very complex trait that depends on the combination of multiple individual compounds that can be measured either destructively or nondestructively during melon ripening. Headspace solid phase microextraction (SPME) or stir-bar sorptive absorption (HSSE, SBSE) to extract and later characterize melon aroma by gas-chromatography mass-spectrometry allow obtaining a melon profile to optimize harvest and purchase experiences. Some aromas typical of recently harvested melons and senescent melons have been identified using NILs. Also, ethylene-dependent and independent aroma during ripening and the principal one from a quantitative and olfactory point of view are reported, mostly acetate, non-acetate and sulfur-derived ester compounds, alcohols and aldehydes in the flesh and also some characteristic terpenes in the skin. Aromatic precursors of these aroma volatiles include lipids but also aminoacids (phenylalanine, methionine, leucine, isoleucine, or valine) or carotenoids. The complexity of quality traits and especially melon aroma requires the application of statistical multivariate methods in order to represent the high-dimensional observed data sets into lower-dimensional spaces to extract the most discriminant features. Partial least squares discriminant analysis (PLS-DA) and random forest (RF) analysis together with some descriptive methods such as principal component analyses are very useful to correlate sensory and instrumental measurements. In addition, these methods have revealed useful to detect interesting QTL effects in near-isogenic lines of melon or to identify the main discriminant differences among melon cultivars. Finally, other statistical techniques such as hierarchical clustering are being tested in order to discern the main metabolic pathways and potential aroma precursors responsible of melon aroma.

            Melon texture is one of the traits more important in the development of the last melon cultivars, particularly because of the great link with “long-life” characters. Firm and crunchy texture seems to be one of the keys of successful new cultivars but having the same flavor than the traditional cultivars. Textural traits with double use such as flesh juiciness or undesirable traits such as mealy texture should be taken into account.

            Many traits reported above are ripening-dependent and particularly ethylene-dependent or ethylene-independent traits. Climacteric types have both kind of traits, but skin color, aroma, texture, or nutrient content are really important in some climacteric types.   Two introgressions of the melon accession PI 161375 into the ´Piel de sapo´ genetic background located in linkage groups III and VI interact epistatically and advances climacteric response due to advanced ethylene biosynthesis. These types of climacteric NILs obtained from non-climacteric parentals have been very useful for diverse quality and physiological studies.

            Mapping QTLs of complex sensory traits and changes in diverse situations of the postharvest chain is still underway. An important variability depending on ethnic and consumer attitude is critical but multivariate methodologies help to determine the main factors in order to determine global quality acceptance. Critical attributes are textural traits in non-climacteric types or retro-nasal aroma and off-flavors in climacteric and aromatic cultivars. However, companies are more prone to use new traits to differentiate new cultivars in the market such as exotic ones as the introduction of a QTL on LG VIII for high acidic-taste melons with increased citric acid content.

The new biotechnological and genomic tools useful for improving melon quality include the sequence of the melon genome, molecular markers, dense genetic maps, TILLING and ECOTILLING platforms, microarrays for gene expression, etc. The integration of this knowledge with cost-effective Next-Generation Sequencing approaches as RNAseq or Genotype by Sequence will speed up the design of new cultivars that will meet consumer expectations under different postharvest scenario.