A reliable screening system for aluminium tolerance in barley cultivars

Aluminium (Al) toxicity in the soil is an important factor that limits the production of barley in areas with acid soil. Selection and breeding of barley cultivars tolerant to Al toxicity is one of the most useful approaches to increase productivity. A reliable screening system is very important for selecting Al-tolerant plants in a breeding program. Using a hydroponic culture technique in which all the treatments were isolated in order to minimise complex interaction between genotypes, experiments were conducted to distinguish between susceptible and tolerant cultivars. Three different methods were investigated. Two previously reported methods could not provide consistent results or detect the difference between tolerant and susceptible cultivars. A new method was developed as follows: pre-germinated seedlings (2 days at 22°C) were cultured for 3 days in nutrient solution (Al free) followed by 24 h growing in a solution with 50 or 100 µm Al, and then 48 h regrowth in Al free nutrient solution. Following this method, seminal root regrowth length (SRRL) and relative seminal root regrowth length (RSRRL) showed significant differences between tolerant and sensitive cultivars. The SRRL of the most tolerant cultivar, Dayton, was 4–8 times greater than of the sensitive cultivars and about twice as long as of the other tolerant cultivars, FM404 and Brindabella. All the sensitive cultivars showed significantly shorter SRRL or RSRRL. Both SRRL and RSRRL were found to be closely correlated with plant height, plant dry weight, and grain weight in a soil-based experiment. This method was also used to evaluate F2 populations from crosses between tolerant and susceptible cultivars. Both SRRL and RSRRL gave results consistent with the hypothesis that the tolerance was controlled by a single dominant gene.