A method of measuring differences between bean varieties in tolerance to sub‐optimal temperatures

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Abstract
SUMMARY: Bean (Phaseolus vulgaris and P. coccineus) plants were grown in controlled environments at (day/night) temperatures of either 25°/20 °C or 20°/15 °C. The lower temperatures tended to reduce the weight of stem relative to the weight of leaf. An interpolation procedure was devised for estimating the magnitude of this effect, which varied between cultivars. It is suggested that the interpolation parameter can be used as an indication of varietal cold tolerance. Thus estimated values of the parameter (h), normalised so that 1 unit = 1 S.E.D, were large and positive in a cv. Seafarer previously characterised as cold intolerant (h = 4–19), large and negative in the relatively cold tolerant P. coccineus cv. Hammond's Dwarf Scarlet (h = ‐3.03), and near to zero (h = 1–11) in the standard commercial variety of P. vulgaris cv. Prelude.The experiment with cvs Seafarer and Prelude was repeated three times and similar values of h were obtained on each occasion. There was only a small variation of h with harvest date; over a period in which plant weight increased at least 3.5 and up to 9 times. In the third experiment a modification of the harvesting procedure was adopted so that plants could be tested for cold tolerance and then grown on for seed production. This semi‐destructive test was applied to, and the results are reported for, nine cultivars which are of interest as potential dry‐bean cultivars for the United Kingdom.