A Quantitative Method to Assess Freezing Resistance in Faba Beans

Abstract

Abstract In order to quantify freezing resistance (R 50 ) of winter faba beans from a limited number of plants, leaves were exposed to artificial freezing stresses with different test temperatures (TT i ). Injury (I i ) was assessed by rating (score: 0—8) and by conductivity measurements. The basic assumption that I i depends almost linearly on TT i over a sufficiently broad range with a constant ΔI/ΔTT could be verified and hence a formula is presented to compute freezing resistance R 50 = (I i —I 50 ) ×ΔTT/ΔI + TT i with I 50 being a medium injury. This formula allows to quantify resistance by assessing I i after freezing test(s) with definite TT i . About 25 leaves are required. Rating appeared preferable to conductivity measurements because of easier and quicker performance and a slightly better discrimination between samples of different resistance. Based on a standardized freezing test, ΔI/ΔTT was determined. Application of the formula with ΔI/ΔTT = 2.5 units/°C for unhardened and hardened leaves, restrictions and experiences are discussed.