Development of a novel aluminum tolerance phenotyping platform used for comparisons of cereal aluminum tolerance and investigations into rice aluminum tolerance mechanisms

Authors: FAMOSO, ADAM - Cornell University; SHAFF, JON - Cornell University; CLARK, RANDY - Cornell University; MCCOUCH, SUSAN - Cornell University; Kochian, Leon

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2010
Publication Date: 8/1/2010
Citation: Famoso, A., Shaff, J., Clark, R., Mccouch, S., Kochian, L.V. 2010. Development of a novel aluminum tolerance phenotyping platform used for comparisons of cereal aluminum tolerance and investigations into rice aluminum tolerance mechanisms. Plant Physiology. 153:1678-1691.

Interpretive Summary: Over 20% of the US land area and approximately 50% of the world’s arable lands are acidic (pH < 5). On these acid soils, aluminum (Al) toxicity is the primary factor limiting crop production as Al is toxic to plant roots, leading to a damaged and stunted root system. As a large proportion of the acid soils are in the tropics/subtropics where many developing countries are located, Al toxicity limits crop production in the very areas where food security is most tenuous. Because of the importance of this problem to agriculture worldwide, there is considerable interest and research effort by researchers at universities, government agencies, and international agriculture organizations in identifying genes that provide tolerance to Al toxicity in order to improve crop Al tolerance via molecular breeding and biotechnology. It has been suggested that rice is the most Al tolerant and all cereals and thus may be a unique genetic research for novel tolerance genes and mechanisms. However, very little is known about the physiology and molecular biology of rice Al tolerance. In this study, we report on the development of improved methods for the hydroponic growth of rice seedlings for Al tolerance research and also the development of an improved digital root imaging system that allowed us to quantify whole root growth, that we show is a more accurate predictor of rice Al tolerance than the longest root methods previously employed.

Technical Abstract: It has been suggested that rice is the most Al-tolerant cereal crop under field conditions, capable of withstanding significantly higher concentrations of Al compared to other major cereals. Therefore, rice may provide novel genetic and/or physiological mechanisms that confer significantly higher levels of Al tolerance than those found in other cereals. However, very little is known about the physiology and molecular biology of rice Al tolerance. Hence, in this paper, we describe the results from a new research project with the ultimate goals of elucidating the molecular and physiological bases of rice Al tolerance. The goals of this study were to 1) quantify Al tolerance in maize, sorghum, wheat, and rice, 2) evaluate the range of phenotypic variation for Al tolerance in diversity panels for rice (233 accessions) and maize (270 accessions)and evaluate the role of subpopulation structure in explaining the variation within each species; 3) develop and optimize a suitable nutrient solution and high-throughput Al tolerance screening method for rice. The findings presented here demonstrated that rice is indeed the most Al tolerant of the cereals. It was also found that the nutrient solutions previously employed for studying rice Al tolerance are flawed, resulting in precipitation of Al, Fe and phosphate. Here we report on improved methods to grow rice seedlings for Al tolerance research and also the development of an improved digital root imaging system that allowed us to quantify whole root growth, that we show is a more accurate predictor of rice Al tolerance than the longest root methods previously employed.