Cold acclimation improves regrowth of cryopreserved apple shoot tips

Area of Science:

• Plant Science
• Cryobiology
• Horticulture

Background:

• Kazakhstan is the center of origin for apples, making its genetic resources vital.
• Safeguarding apple germplasm through cryopreservation is crucial for biodiversity and future breeding efforts.

Purpose of the Study:

• To determine the cold hardiness of apple genotypes.
• To evaluate the impact of cold acclimation on shoot tip recovery after cryopreservation using two methods.

Main Methods:

• Five apple genotypes (Malus domestica and Malus sieversii) were subjected to cold acclimation (CA) for 0-6 weeks.
• Shoot tips were cryopreserved using PVS2 vitrification and encapsulation dehydration (ED).
• Cold hardiness was assessed by lethal temperature 50 (LT50), and shoot tip regrowth was measured.

Main Results:

• Non-acclimated shoot tips had LT50 values between -6.7°C and -9.3°C, with 10-12% regrowth.
• Cold acclimation for 1-3 weeks increased hardiness (LT50: -12°C to -15°C) and resulted in up to 65% regrowth.
• No significant difference in regrowth was observed between PVS2 vitrification and encapsulation dehydration.

Conclusions:

• 2-5 weeks of cold acclimation significantly enhances cryopreservation recovery rates for Malus germplasm.
• A standard protocol of three weeks of alternating temperature cold acclimation is recommended for apple germplasm cryopreservation.
• This protocol yields moderate to high recovery (60-80%) across tested genotypes using both cryopreservation techniques.