## 2 Materials and Methods  
### Plant Material  
From September to October 2021, chestnuts were collected from the germplasm repository (_Castanetum_) of the Chestnut R&D Center--Piemonte, located in Chiusa di Pesio (CN) in Piedmont (North-Western Italy) (44\({}^{\circ}\)19\({}^{\prime}\) N, 7\({}^{\circ}\)40\({}^{\prime}\) E; elevation 575 m above sea level). The area is characterized by a temperate climate, with an average annual rainfall of approximately 1350 mm, very important for the high-water requirements of _Castanae_ spp. (Figure 1). The soil is classified as a well-draining Entisol with a sandy-loam texture, abundant in the skeleton (>35%), but with limited depth (<25 cm). Despite this limitation, moderate summer temperatures and high rainfall in the area enable a balanced growth of the trees. Additionally, the soil is favorable for the growth of chestnut trees because of its very low levels of carbonates and a pH range between 4.5 and 6.5. In the _Castanetum_, the plants grow up in the same pedoclimatic conditions and they are grafted on the same clonal rootstock, significantly reducing their variability due to environmental factors, and highlighting the differences derived from the genotype. The orchard layout is 8.0 m \(\times\) 11.5 m and each cultivar is represented by 3 individuals. The inter-row is grassed and the row is covered with mulch; irrigation is only for emergency purposes. The fruits were grouped in accordance with their genotype in four groups: Japanese chestnuts (_C. crentata_), Euro-Japanese hybrids (_C. sativa_\(\times\)_C. crentata_), and European chestnuts (_C. sativa_ sweet chestnuts and _C. sativa_ \"marrone-type\"), as shown in Table 1.  
Figure 1: Meteorological data recorded in 2021 by the weather station located in the _Castanetum_; the numbers above the columns indicate the number of rainy days in the corresponding month. Source: ARPA Piedmont. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Species** & **Cultivar** & **Origin** & **ID Sample** \\ \hline
1 & & Ginyose & & D18 \\ \hline
2 & & Ishizuki & & F23 \\ \hline
3 & _C. crenata_ & Ishizuki Precoce & Japan, Korea, North-East China, Taiwan & O15 \\ \hline
4 & & Ishizuki Tardiva & & E17 \\ \hline
5 & & Tsukuba & & G14 \\ \hline
6 & & Bouche de Bétizac & France & I10 \\ \hline
7 & & Colossal & East USA & M22 \\ \hline
8 & & Lusenta & Italy (Piemonte) & M15 \\ \hline
9 & & Maridonne & & J14 \\ \hline
10 & & Marigoule & & J13 \\ \hline
11 & & Marissard & & N14 \\ \hline
12 & & Marlhac & France & K05 \\ \hline
13 & & Marsol & & F06 \\ \hline
14 & & Precoce Migoule & & G18 \\ \hline
15 & & [PERSON] & & I17 \\ \hline
16 & & Biancole della Garfagnana & Italy (Toscana) & B03 \\ \hline
17 & & Bouche Rouge & France (Ardéche) & I18 \\ \hline
18 & & Castagna della Madonna & & G01 \\ \hline
19 & & Ciapastra & Italy (Piemonte) & T02 \\ \hline
20 & & Contessa & & L02 \\ \hline
21 & & Dore de Lyon & Central-West France & H23 \\ \hline
22 & & Epinerere & Italy (Valle d’Aosta) & M16 \\ \hline
23 & & Gabiana & & O03 \\ \hline
24 & & Garrone Rosso & Italy (Piemonte) & I03 \\ \hline
25 & & [PERSON] & & P12 \\ \hline
26 & & [PERSON] & Portugal (Padrela) & F21 \\ \hline
27 & & Laguepie & France & H24 \\ \hline
28 & & Longal & Portugal (Terra Fria) & E16 \\ \hline
29 & & Marrubia & Italy (Piemonte) & Q13 \\ \hline
30 & & Neirana & Italy (Piemonte) & U09 \\ \hline
31 & & Nerone & Italy (Toscana) & H08 \\ \hline
32 & & Primemura & Italy (Piemonte) & X05 \\ \hline
33 & & Primitiva di Roccamonfina & Italy (Campania) & I07 \\ \hline
34 & & Pugnenga & Italy (Piemonte) & P04 \\ \hline
35 & & Rossane & & N13 \\ \hline
36 & & Ruffinette & Italy (Valle d’Aosta) & N13 \\ \hline
37 & & Ruiana & Italy (Piemonte) & M11 \\ \hline
38 & & Savoye & France (Dordogne, Lot, Cantal) & J16 \\ \hline
39 & & Tarvisó & & U06 \\ \hline
40 & & Tempuriva & & O12 \\ \hline
41 & & Toumive & France (Cantal-Mourjou) & D11 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of _Castanene_ species and respective cultivars subject to analysis.