Plūmju šķirņu ziedpumpuru un koksnes salcietības pārbaude kontrolēta klimata apstākļos = Evaluation of frost resistance of plums cultivars floral buds and wood in artificial climate conditions

The study of flower bud frost resistance at the Institute of Horticulture was started on 19.02.2024, when the deep dormancy period of plums had ended. The study includes the new plum cultivars ‘Laine’, ‘Zane’, the promising hybrids ZJ-110212, AJ-110207; AJ-110208 isolated during the Breeding Project, as well as the control cultivar ‘Victoria’, which has been grown in Latvia for a very long time and is found in all regions, both in commercial gardens and in home gardens. The winter hardiness of cultivars and hybrids was evaluated in artificial conditions using a climate chamber. The temperature was lowered by 2 degrees per hour. At the beginning of the study, the existing state of the wood of the buds and branches before freezing (control variant) was determined. Temperature regimes: -10, -15. -20, -25, -30°C. Plant parts under study: buds on annual branches, buds on fruit twigs, annual branches, perennial branch wood (2 or 3-year-old wood part for fruit branch). In the control variant, neither buds nor wood were damaged for the cultivar ‘Laine’, hybrids ZJ-110212 and AJ-110208; some buds were partially damaged, but the wood was intact for the cultivars ‘Zane’ and ‘Viktoria’; some buds were damaged and the fruit branch wood was slightly browned for the hybrid AJ-110207. When the temperature was lowered to - 25°C, only the cultivar ‘Laine’ retained 37% healthy flower buds on annual branches and 29% on fruit branches (according to scientific literature, 25% fertilized flower buds are sufficient to obtain a normal yield of stone fruit trees). This means that in adverse spring conditions, the cultivar ‘Laine’ could yield a crop in the garden. The wood of this cultivar is also slightly browned, but with a healthy cambium. Even at -30°C, the cultivar ‘Laine’ has preserved 14% healthy flower buds on annual branches and 9% on fruit branches, preserving live cambium, which can restore damaged wood tissue. According to the results obtained in 2024, the cultivar ‘Laine’ and the hybrid ZJ-110212 have the highest flower bud durability and the most winter-hardy wood, significantly exceeding the indicators of the control cultivar ‘Victoria’.