Effect of recurrent selection for aluminum tolerance on shoot morphology and chemical content of white clover

Abstract

This study compares the effect of aluminum (Al) on the shoot morphology, root distribution and plant chemical content of selections made for Al tolerance and an unselected population of Huia white clover (Trifolium repens L.). Seedlings from the two seed sources were sown into trays of soil to which had been added 400 μg Al/g soil as aluminum sulphate. The two seed sources were, (1) progeny from a polycross of genotypes previously selected for Al tolerance from the cultivar Huia and, (2) a previously unselected accession of Huia. After selection of genotypes capable of producing large shoots when grown in soil containing 400 μg g^‐1 added Al, plants were grown in artificial soil profiles where soil Al content increased with depth. Selections from first generation Al‐tolerant germplasm were smaller leaved, with more leaves per unit length of stolon, with larger stolons, heavier shoots and a slightly deeper root distribution, but lower root/shoot ratio than selections from previously unselected germplasm. The proportion of root weight below 100 mm (i.e., the proportion of root growing in Al‐toxic soil) was poorly related to other characters measured. From an analysis over all 100 genotypes tested, proportion of root weight below 100 mm was significantly (P <0.05) but weakly (r=0.19) correlated with shoot [potassium/(calcium + magnesium) (K/(Ca + Mg))] ratio. Selection for Al tolerance in white clover can cause associated changes in other plant characters.