Induction of rhizogenesis in Prunus dulcis (Mill.) D.A. Webb by nutritional and hormonal determinants

Almond (Prunus dulcis) is one of the promising nut-bearing crops capable of mitigating climate risks to achieve sustainable development goals and prevent threats to agroecological and food security. For the rapid propagation of high-quality planting material, microclonal propagation is the most suitable method, carried out under controlled conditions in four stages. The success of rhizogenesis (one of the stages) determines further survival of regenerants during the adaptation phase. The study was carried out under standard conditions in the interdepartmental plant biotechnology laboratory of BNAU. Explants of four domestic sweet almond cultivars («E5 Borozan», «M 41 Alex», «Georgia», «Louise») were used in the research. We studied the influence of nutritional and hormonal determinants on sweet almond rhizogenesis. The results demonstrate varietal specificity of almond reactions to auxin type, phytohormones ratio, and other technological determinants. The study of the effect of synthetic auxin analogues (indolebutyric, indoleacetic, naphthylacetic acids) on the induction of rhizogenesis has established that the optimal conditions for root formation are the use of indolebutyric acid at a concentration of 0.75 mg/l in combination with 0.125 mg/l BAP. The concentration of sucrose (1–2 %) promotes the formation of a developed root system and improves the biometric indicators of regenerants. Higher sucrose concentrations led to tissue hyperhydration and callus formation, complicating plant adaptation. The effect of mesoinositol and activated charcoal was also studied, revealing that moderate concentrations improved root formation. The optimal conditions were determined to be the addition of 2% sucrose and 1.0–1.5 g/L of activated charcoal. Therefore, the research results showed that the effectiveness of sweet almond rhizogenesis in vitro depends on many factors, among which the type of explant, the hormonal ratio in the medium, and its trophic composition. Optimization of these parameters at the stage of rhizogenesis is key to increasing productivity in microclonal propagation of this crop.