Hail net cover, cultivar and pod size influence the chemical composition of dwarf French bean

• Hail net covering alter microclimatic conditions and chemical profile of bean pods.
• Microclimatic conditions under the net caused a lower content of monosaccharides.
• Net protection influenced the composition of sugars in yellow pod cultivars.
• Vitamin C was decreased under hail net protection more in green pod cultivars.
• Decrease in Total Phenolic Content was confirmed under protection, only with green pod cultivars.

Dwarf French bean is cultivated in the open field, where unpredictable extreme weather events decreased crop yield quality. Hail net protection is therefore desirable. The pods are a rich source of sugars, organic acids and phenolic compounds and, as such, are an important nutritional vegetable. Due to consumer demand for half-sized pods in some traditional cuisines, the chemical profile of both pod sizes are desired. The aim of the study was to determine the effect of hail net covering on microclimatic conditions, specifically on light interception and temperature modification and, consequently, on the chemical profile of bean pods harvested in two sizes. The experiment was treated as a split–split plot designed three factorial experiment in four randomized replications. The main factor ‘covering’, had two levels, (hail net covered and uncovered plots); the sub-factor ‘cultivar’ had four levels, (‘Berggold’, ‘Re dei burri’ ‘Paulista’, ‘Top crop’) and the sub–sub-factor ‘pod size’, had two levels (half-size and full-size pods). Individual sugars and organic acids were analyzed, using high-performance liquid chromatography (HPLC). Total phenolic content was determined by spectrometry. Lighting was measured as the amount of photosynthetic active radiation (PAR). PAR under the hail net was reduced by 30–75% and mean daily temperature by 2.4 °C in comparison with the control. Significant genotypic effect was confirmed for vitamin C, while sugars, organic acids and total phenolics are affected mostly by interaction of two or three factors. Higher vitamin C content was found in cultivars classified as anthracnose resistant (‘Berggold’ and ‘Paulista’) compared to not resistant cultivars (‘Re dei burri’ and ‘Top crop’). Covering decreased fructose, glucose and vitamin C contents. Total phenolics were decreased under hail net only in pods of green pod cultivar. Hail net also influenced the composition of individual sugars in yellow pod cultivars (‘Berggold’ and ‘Re dei burri’), with which sweeter pods were harvested, with a higher fructose/glucose ratio. Pod size also significantly affected all chemical compounds analyzed bean pods. Younger half-sized pods had higher fructose and glucose content, as well as malic and citric acids and also total phenolic content, compared to full-sized pods. On the other side, younger pods contain significant lower amount of vitamin C and sucrose compared to older pods. Significant genotypic variation connected with hail net covering observed within yellow pod cultivars, provides opportunities for the plant breeders to develop special genotypes for maximizing the nutraceutical value of bean pods under hail net production.