A Thermosensitivity Index for Lupinus albus L

Abstract

Phenology and plant architecture of spring lupin Lupinus albus L. vary with early thermal environment, which dramatically affects seed maturation and production. This study was conducted to develop and evaluate an index to quantify the relative differences among a selection of genotypes to “warm” and “cold” temperatures during early development. Seedlings of 27 lupin accessions and cultivars were incubated at 5 and 24°C for 3 wk and then grown to maturity in the greenhouse. The number of mainstem vegetative nodes at maturity were counted and used as the basis for developing an index of thermosensitivity. The simple difference between mainstem vegetative node numbers from seedlings incubated at 24 and 5°C provided a means for quantifying thermosensitivity and identifying thermoneutral genotypes. Significant simple difference values ranged from 4.69 to 20.33 and were not significant for cv ‘start’. An alternative standardized index was developed that allowed for comparisons within genotypes among years.