Chilling Requirement: A Main Step to Get Productive Response in Walnut and Pecan Cultivars in Catamarca (Argentina)

The thermal requirements of deciduous fruit trees are crucial for expanding walnut and pecan cultivation in Catamarca, a warm region in northwestern Argentina. This study evaluated the chilling requirements of two Persian walnut cultivars (‘Chandler’ and ‘Trompito INTA’) and three pecan cultivars (‘Stuart’, ‘Pawnee’, and ‘Western’). Well-lignified budsticks, one-year-old branches of ۴۰ cm, were removed from trees twice, in the autumns of ۲۰۱۸ and ۲۰۱۹, without damaging any apical (TB) or lateral buds (LT). They were stored at ۵ ± ۰.۵°C to accumulate chilling hours (CH) across ten treatments (۰-۱۰۰۰ CH in ۱۰۰ CH intervals) before sprouting in greenhouse conditions. Results were quantified as the mean time (days) to reach budbreak (MTB) and as the percentage of budbreak. The ‘Western’ pecan required the least chilling (۳۰۰-۴۰۰ CH), followed by ‘Pawnee’ (۴۰۰-۵۰۰ CH) and ‘Stuart’ (۶۰۰-۸۰۰ CH). It should be noted that the pecan tree in cvs 'Pawnee' and 'Western' sprouted without cold in the first-year trials. Considering walnut, ‘Trompito INTA’ and ‘Chandler’, showed a chilling requirement of ۵۰۰ and ۸۰۰ CH, respectively. Persian walnuts needed at least ۲۰۰ CH to budbreak. The study shows that pecan requires less cold to reach ۵۰% sprouting than to stabilize MTB. ‘Trompito INTA’ stands out as a Persian walnut cultivar with low chilling requirements. This cultivar may be better adapted to milder winters and could contribute to climate change adaptation in walnut-growing regions. These results are valuable for cultivar selection and planning expansion of nut orchards in warm regions of Argentina

کلیدواژه ها:

J. regia L ، C. illinoinensis Koch ، Chill requirement ، Heat requirement ، Budbreak ، dormancy