Genome wide association mapping for agronomic, fruit quality, and root architectural traits in tomato under organic farming conditions

[EN] Background Opportunity and challenges of the agriculture scenario of the next decades will face increasing demand for secure food through approaches able to minimize the input to cultivations. Large panels of tomato varieties represent a valuable resource of traits of interest under sustainable cultivation systems and for genome-wide association studies (GWAS). For mapping loci controlling the variation of agronomic, fruit quality, and root architecture traits, we used a heterogeneous set of 244 traditional and improved tomato accessions grown under organic field trials. Here we report comprehensive phenotyping and GWAS using over 37,300 SNPs obtained through double digest restriction-site associated DNA (dd-RADseq). Results A wide range of phenotypic diversity was observed in the studied collection, with highly significant differences encountered for most traits. A variable level of heritability was observed with values up to 69% for morphological traits while, among agronomic ones, fruit weight showed values above 80%. Genotype by environment analysis highlighted the strongest genotypic effect for aboveground traits compared to root architecture, suggesting that the hypogeal part of tomato plants has been a minor objective for breeding activities. GWAS was performed by a compressed mixed linear model leading to 59 significantly associated loci, allowing the identification of novel genes related to flower and fruit characteristics. Most genomic associations fell into the region surrounding SUN, OVATE, and MYB gene families. Six flower and fruit traits were associated with a single member of the SUN family (SLSUN31) on chromosome 11, in a region involved in the increase of fruit weight, locules number, and fruit fasciation. Furthermore, additional candidate genes for soluble solids content, fruit colour and shape were found near previously reported chromosomal regions, indicating the presence of synergic and multiple linked genes underlying the variation of these traits. Conclusions Results of this study give new hints on the genetic basis of traits in underexplored germplasm grown under organic conditions, providing a framework for the development of markers linked to candidate genes of interest to be used in genomics-assisted breeding in tomato, in particular under low-input and organic cultivation conditions.This research was supported by the European Union Horizon 2020 Research and Innovation program for funding this research under grant agreement No 774244 (Breeding for Resilient, Efficient and Sustainable Organic Vegetable Production; BRESOV) and by 'RGV-FAO'project funded by the Italian Ministry of Agriculture, Food and Forestry. The funding bodies were not involved in the design of the study, collection, analysis, and interpretation of data, and in writing the manuscript.Tripodi, P.; Soler Aleixandre, S.; Campanelli, G.; Díez Niclós, MJTDJ.; Esposito, S.; Sestili, S.; Figás-Moreno, MDR.... (2021). Genome wide association mapping for agronomic, fruit quality, and root architectural traits in tomato under organic farming conditions. BMC Plant Biology. 21(1):1-22. https://doi.org/10.1186/s12870-021-03271-412221

Adaptive Responses to Nitrogen and Light Supplies of a Local Varieties of Sweet Pepper from the Abruzzo Region, Southern Italy

Local varieties represent a heritage for plant biodiversity and, thanks to their resilience, are characterized by a better adaptation and rusticity to environmental variables. This work reports the morphological and physiological responses of a local ecotype of sweet pepper grown in Southern Italy, i.e., Altino, to N and light supplied at optimal and sub-optimal levels. In 2017, two open-field experiments were set up, comparing increasing N rates (0, 100 and 200 kg N ha−1, 0_N, 100_N and 200_N, respectively) and different percentages of shading and/or manipulations of the transmitted solar radiation, obtained through photoselective nets (red net, RN; black net, BN; unshaded Control). The unfertilized plants reduced growth (by 32% on average, at 83 days after transplanting, DAT), especially in terms of number of leaves, leaf area and effectiveness (chlorophyll content) of photosynthetic apparatus; no differences were recorded among fertilization treatments. On the other hand, the shading avoidance mechanisms resulted in higher biomass partitioned to leaves at the expense of sink organs, the building of more expanse (higher total leaf area) and thinner (higher specific leaf area and lower leaf-cuticular waxes) photosynthetic apparatus, and in a greater concentration of leaf pigments. The effects on yield and fruit quality of Altino ecotype deserve to be further explored

EFFECT OF SALINITY STRESS ON PHYSIOLOGICAL FACTORS AND PHYTOCHEMICAL COMPOUNDS IN LETTUCE (LACTUCA SATIVA L.)

moderate salinity induced the highest phytochemical content in lettuce tissues without affecting yield. Spectra vis region can discriminate between salinity treatment

Modulation of Light and Nitrogen for Quality-Traits Improvement: A Case Study of Altino Sweet Pepper

Local varieties are known to cope more efficiently with stressful and/or low-input conditions than cultivated ones by activating secondary metabolisms and, hence, are supposed to have higher nutraceutical potential. In this work, we investigate the effects of N and light, supplied at optimal and sub-optimal levels, on the fruit yield and quality of a local ecotype of sweet pepper, Altino, grown in the Abruzzo Region (Southern Italy). In 2017, two open-field experiments were carried out, comparing increasing N rates (0, 100 and 200 kg N ha−1, 0_N, 100_N and 200_N, respectively) and different percentages of shading and/or manipulations of the transmitted solar radiation, obtained through photoselective nets (red net, RN; black net, BN; unshaded Control). Both N and light were preconditions to obtain stable yields in terms of both fruit number and fruit weights. However, BN significantly reduced the number of sunscalded fruits (0.39 vs. 3.38 and 2.59 fruit plant−1 for BN, Control and RN, respectively), leading to lower waste. N deficiency favoured higher total polyphenol (TPC) and flavonoid (TFC) contents in ripened fruits; on the other hand, shading significantly reduced TPC (−12.4%) in immature and TFC (−18.2%) in red fruits. The variations in nutraceuticals were also evaluated in terms of the variations of the single phenolic acids in fruits during ripening; the most interesting results were associated with light treatments. Further research should be directed to the in-depth study of nutrition regimes, in combination with other photoselective nets applications (i.e., pearl nets), that could be suitable for the Altino genotype to enhance the yield and nutraceutical potentials of its fruits

Nitrate Content Assessment in Spinach: Exploring the Potential of Spectral Reflectance in Open Field Experiments

A rapid, non-destructive method for nitrate content assessment is essential for a rational wide-scale application of nitrogen in sustainable growing spinach. The method should be effective in facing environmental, genotype, and management variability. The results from three field experiments carried out in Teramo (Italy), during the 2021 and 2022 growing seasons, and by combining nitrogen supply with spinach genotypes, are presented. The spectral canopy reflectance was collected to find out the spectral band relationship with nitrate concentration. Preliminary PCA and mixed linear model analysis showed that nitrate content is among the less detectable features. Unexpected chlorosis onset in one experiment added more variability; nevertheless, spectral regions of blue-cyan and early NIR when combined into Vegetation Indexes were able to correlate to nitrate content with R2 up to 0.65 in all experiments. This study demonstrates that focusing on just a few spectral regions facilitates the acquisition of suitable and robust information on nitrate content in spinach