Julia Hagenguth

Fresh market tomatoes are often characterized by poor flavour. Flavour is a quantitative trait difficult to assess and often neglected in breeding. Classical sensory methods are not suitable for the evaluation of early segregating generations; simple physicochemical measurements are not sufficient to predict perceived aroma. Alternative selection methods are needed, such as the recently introduced Breeders' Sensory Test or marker‐assisted selection (MAS). Two unrelated crosses were chosen to evaluate the efficiency of phenotypic selection with the Breeders' Sensory Test (breeders' sensory selection, BS) and MAS for five quantitative trait loci for sweetness, sourness and tomato aroma (mapped in ‘Resi’ × ‘Auriga’) in organic low‐input and hydroponic cultivation. Selection for sensory attributes reduced fruit weight, emphasizing the challenge of breeding flavourful, large‐fruited tomatoes. Both selection methods were more effective in ‘Roterno F₁‘× ‘Black Cherry’ derived from more distant parents. A trend towards higher efficiency of MAS in early segregating generations was observed for sweetness and tomato aroma. However, a major advantage of BS is its universal applicability. To improve flavour, combining both methods is recommended.

Human sensory analysis is the most appropriate method for assessing the flavour of fresh market tomatoes, but it is very labour and time consuming. Therefore, sensory attributes are often neglected in early generations of breeding programmes and genetic studies, although there is a demand for tomatoes with improved flavour. In this study, the recently developed Breeders' Sensory Test was applied to an F₂mapping population derived from two parents with superior flavour. Sensory attributes, physicochemical measurements, volatiles and fruit weight were assessed in organic low‐input and hydroponic cultivation. A linkage map spanning 1070 cM was developed. In total, 71 quantitative trait loci (QTL) were detected for the means of both cultivation systems, 61 for organic and 46 for hydroponic cultivation. A proportion of 27% of the loci were co‐localized between both cultivation systems. Nine distinct QTL clusters for flavour‐related traits were identified, including a large cluster on chromosome 6 comprising five sensory and nine volatile QTL. The sensory QTL on chromosomes 2, 5, 6, 10 and 11, partly within clusters, are recommended for marker‐assisted selection.

For several decades, improved flavour has not been a main focus in tomato breeding because it is difficult and expensive to evaluate. Sensory panels are designed to assess flavour, but they are not able to evaluate large sample numbers typical for early breeding generations. Selection in the first segregating generation could enhance breeding for flavour by preventing the loss of favourable alleles. The efficiency of early selection is unknown due to the polygenetic inheritance of flavour. To address these issues, F₂ plants from 32 crosses and their parents (910 individuals) were evaluated for aroma, sweetness and sourness with the Breeders' Sensory Test (small team and large number of small samples from individuals), as well as for physicochemical traits (total soluble solids, titratable acidity and dry matter), and volatile compounds in low‐input organic and hydroponic cultivation. Corresponding physicochemical and sensory traits were significantly correlated. For most of the studied traits, it was possible to select between single plants in the F₂ generation. Thus, the Breeders' Sensory Test can be used as a new tool in breeding for flavour.

The yield and fruit quality parameters of tomatoes are influenced by environmental conditions, and cultivation systems play an important role in improving quality, apart from breeding. We examined five breeding lines and one cultivar in five cultivation systems for yield and fruit quality parameters. The cultivation systems include a single-glazed greenhouse with and without supplementary LED interlighting; a double-glazed greenhouse with and without supplementary LED interlighting; and an organic cultivation system on the field with a rainout shelter. Plants and fruits grown in the double glazing system showed significantly lower values for plant height, yield, DM, TSS, fructose, glucose, antioxidant capacity (DPPH, TEAC), TPC, calcium, phosphorus, and manganese content than in the single-glazed greenhouse, which can be explained by the lower light transmittance. However, it could be seen that the additional LED interlighting could lower the negative effect on yield and quality traits due to double glazing.