Aluminum Tolerance of 1BL.1RS and 1AL.1RS Near‐Isolines in Soft Red Winter Wheat

Abstract

Some cultivars containing the 1BL.1RS wheat (Triticum aestivum L.)‐rye (Secale cereale L.) translocation are presumed tolerant to aluminum (AI) toxicity, but whether this tolerance is due to genes 1RS or to genes in the wheat genome is not clear. A set of backcross‐six, F2‐derived F4 near‐isolines containing either the ‘Kavkaz’‐derived 1BL.1RS or ‘Amigo’‐derived 1AL.1RS translocation were developed in five soft red winter wheat backgrounds at Columbia, MO between 1988 and 1992. The presumed contribution of 1RS to Al tolerance expressed in solution culture was measured using a split‐plot design, replicated four times. Seedlings were grown for 4 d in an aerated, low‐ionic‐strength, hydroponic solution at pH 4.0 containing no phosphorus. Whole‐plot treatments included 1 mg L−1 Al as AlCl3 and a zero Al control. The longest seminal root of each seedling was measured and averaged across seven seedlings per isoline. Root tolerance index (RTI), calculated as the mean seminal root length in the Al treatment divided by the mean seminal root length in the control, provided a measure of Al tolerance. Higher RTI values indicated greater Al tolerance. Mean RT1 values for each background, averaged across 1AL.1RS and 1BL.1RS isolines, ranged from 0.63 in ‘MO 11728’ to 0.24 in ‘Caldwell’. 1AL.1RS significantly reduced Al tolerance in ‘Becker’, Caldwell and ‘MO 10501’, but had no effect on A1 tolerance in MO 11728 and ‘Pioneer 2551’. 1BL.1RS had no effect on Al tolerance in any genetic background. Neither the Kavkaz‐ nor the Amigo‐derived 1RS segment contained genes for AI tolerance when grown in solution culture, and improved AI tolerance previously reported in 1BL.1RS cuitivars was due to coincidental major genes on the wheat genome.