Differential acclimation capacity to frost in sugarcane varieties grown under field conditions

In certain sugarcane (Saccharum spp. hybrids) production regions of the world, including South Africa, frost frequently occurs. Great demand exists for frost tolerant sugarcane varieties as production in these areas could become more profitable. Two Louisiana (USA) varieties, known to yield high sugar even when immature (LCP 85-384 and HOCP 96-540), and two South African varieties (N21 and N36) were evaluated in a field trial for frost tolerance. O–J–I–P chlorophyll a fluorescence transients were recorded in youngest fully-expanded leaves of these varieties on several occasions before and following exposure to frost. Analysis of these transients revealed that varieties N36 and LCP 85-384 were capable of cold acclimation following the first frost, while N21 and HOCP 96-540 lacked similar capability. Exposure to further frosts altered the fluorescence transients in a variety-specific fashion, with recovery in N36 and LCP 85-384 towards baseline kinetics, but with further deterioration in N21 and HOCP 96-540. Between the first frost and harvest, estimated recoverable crystal (ERC) content values in cane stalks of N36 and LCP 85-384 increased by 26 and 20 % respectively, while in N21 and HOCP 96-540 ERC content values only increased by 8 and 11 % respectively. Consequently, N36 and LCP 85-384 ultimately achieved the highest ERC yields (tons/hectare). The ability to maintain high ERC accumulation capacity for longer following frost could be an important factor determining sugarcane yield performance in frost-prone areas. In addition, O–J–I–P fluorescence rise kinetics show promise as a rapid screening tool for assessment of cold acclimation potential in sugarcane.