The main objective of this WP is to develop new tools to be used in the pre-harvest production process. Attention will be focused in particular on: a) Fruit load control: alternative thinning practices and genetic surveys on self-thinning characters;b) Water management to control fruit quality: assessment of ABA efficacy; c) Fruit growth, build up of nutrients and ripening process evolution: innovative measuring tools.
WP3a1 Alternatives to conventional thinning methods.
The new cultivars recently released by the breeding programmes are characterized by a very high fertility and do require intense thinning to allow high fruit quality and size, and avoid alternate bearing. In some areas the traditional plant bioregulators (auxin, NAAm, and BA) used as thinners do not always give satisfactory results, because of the climatic conditions favouring fruit set and retention, typical of hill and mountain production areas. In such environmental conditions, new fruit thinning strategies must be set up and tested, such as the use of metamitron, a chemical available in a new formulation and extremely effective on cultivars difficult to thin. However, since sustainability must be taken into consideration, new environment-friendly chemicals must be experimented, such as vegetal oil, lime sulphur, and fertilizers (ATS) to enlarge the range of thinners potentially used in different situations and cultivars. An alternative approach, the mechanical thinning, must be also tested. Darwin machine, lately assessed by Creso, is characterized by high efficiency. Use conditions, such as tractor speed, spindle rotation speed and string length will be further analyzed for different cultivars and orchard management. The interaction between orchard training system and mechanical thinning devices will also be studied. In the Fruit Research Centre of CReSO, dedicated systems, such as close multiple axis (bibaum®, etc.), have been set up for testing tree architecture suitability to mechanical thinning devices and assessing field efficacy (yield and average fruit weight, alternate bearing). Potential constrains (i.e. induction of fire blight) will eventually be investigated.
WP3a2 Molecular genetics and functional genomics of fruit load control and self-thinning.
An experimental cross population of 192 F1 plants, segregating for self-thinning has been produced at FEM-IASMA and is now at the second year of fruiting. Preliminary analysis showed a clear segregation for self-thinning (both at the levels of flowers within corymb and corymbs). Two linkage maps (one for each of the two parental meiosis) based on ca. 300 SNP and ca. 100 SSR markers (for a total of at least 20 informative markers per chromosome) will be produced. A number of self-thinning related phenotypes (number of corymbs per branch, number of flowers per corymb, number of fruitlets per corymb and branch) at several time points during the growing season will be collected during the three years of the project, and utilized for QTL analysis. The Golden delicious genome sequence (available at FEM-IASMA) will be searched for candidate genes subtending the major self-thinning QTLs.
The identification of candidate genes potentially involved in the regulation of fruit drop will finally provide useful markers for chemical responsiveness of genotypes. This will be undertaken by microarray-based analyses of the transcriptomes of abscising and non-abscising fruits. To this purpose, cultivars sensitive or recalcitrant to thinning chemicals as well as genotypes with different self-thinning aptitude will be evaluated for their molecular responses to different chemical treatments. Preliminary data obtained at DAAPV have enabled to reliably differentiate between abscising and non-abscising fruits by exploiting targeted approaches, on the basis of hormonal responses (ethylene) and physiological parameters. The diagnostic power of these approaches will be exploited to dissect and identify the molecular determinants of fruit drop in a robust way. Particular attention will be devoted to the contribution of different tissues (seed or cortex) to the destiny of fruits. The genes identified by these approaches will be assessed for their potential usage as markers for the early identification of the self- or chemical-thinning aptitude of apple cultivars. (UNIPD)
WP3b Water management to control fruit quality.
This task aims to evaluate the efficacy of a recent innovative formulation of ABA which allows the application in field conditions. ABA treatments will be performed in trials concerning the irrigation study as well as in those specifically related to fruit quality enhancement. In the first case, an analysis of the apple “physiological water demand” will be performed by precision probing and the effect of ABA-based chemical on stomata functioning will be considered. In addition, the effect on fruit quality will be studied, taking into account that endogenous ABA is involved in the fruit ripening syndrome and assimilate accumulation and maintain its physiological role also in limited water availability conditions. In addition, the effect of the hormone formulation on sugar signalling pathways will be studied by means of a molecular approach. In detail, the transcriptional profiles of genes involved in ABA biosynthesis and carbohydrate metabolisms will be analyzed in apple fruit during development.
WP3c1Real time management of crop load and fruit growth based on the geo-spatial analytical method.
The existing know-how on modeling of apple fruit growth will be implemented. Fruit diameter data will be collected on selected trees within the experimental plot according to a protocol specified by DCA-UniBO. The data will be processed via proprietary algorithms and a diagnosis will be released as to the appropriateness of crop load on the monitored trees.
The reliability of real time site monitoring of fruit size will be verified. Data will be collected adopting state of the art geo-spatial analytical methods (Manfrini et al. 2009).
In this approach the following assessments of the evolution of crop quality traits will be provided in real-time: fruits size at harvest (forecast released every week), fruit size class distribution at harvest (released on average one month before harvest).
WP3c2 Innovative measuring tools for monitoring the build up of nutrients and the fruit ripening process.
The Department of Fruit Tree and Woody Plant Sciences of the University of Bologna developed a simple device (DA-Meter) which allows to define the ripening stage reached by the fruits in a more simple and rapid way. The DA-Meter is a portable, user-friendly vis/NIRs device capable of measuring an Index of Absorbance Difference (IAD) which do express with accuracy the ripening stage of the fruit. The DA-Meter is formed by 6 diode LEDs, all positioned around the photodiode detector, 3 diode LEDs emit at 670 nm wavelength and the other 3 emit at 720 nm. Based on fruit absorbance spectra, the IAD is calculated as IAD = A670 – A720 where A670 and A720, near the chlorophyll-a absorbance peak, were the A values at the wavelengths of 670 and 720 nm, respectively. The use of the DAmeter aims to evaluate under field conditions the difference in the fruit maturation/growth evolution according to the position within the canopy (light exposed or shaded), and type of bearing shoot (1 year old shoot , spur, etc). According to the differences detected, a decision will be taken to properly prune to increase the homogeneity of the ripening of the fruits at harvest. If this objective will be achieved, the batch of fruits harvested will be characterized by a uniform ripening stage and all the subsequent operations, such as harvest time definition, storage strategy choice, the type of market, the eventuality to apply chemical tools (such as 1-MCP to prolong storage and shelf-life), etc. will be precisely established. All these data will be collectively used to generate density maps of the experimental orchard and previous year data will be used to refine the experimental protocol of the subsequent year.