A method to identify lupin species tolerant of alkaline soils

Narrow-leafed lupins (Lupinus angustifolius L.) grow poorly on alkaline soils. In contrast, L. pilosus Murr. and L. atlanticus Glad. grow well on such soils. This study aimed to develop a solution culture method to screen lupin species for their ability to grow well on alkaline soils.Sixteen lupin genotypes from 6 species, including introduced cultivars and wild types, were grown in high pH solutions with varying concentrations of buffers and bicarbonate. Relative taproot elongation, shoot growth and iron chlorosis were compared with iron chlorosis, relative shoot growth and seed yield for the same genotypes on an alkaline soil in the field. The results suggested that root elongation rate at pH 7 in solution buffered with a mixture of 1 mmol MES/L and 1 mmol TES/L (plus 10 mmol CaCl2/L), and shoot weight at 5 mmol bicarbonate/L at pH 8.7 are good indicators of tolerance to an alkaline soil among the lupin species.