|MATONYEI, T. - Moi University
|CHEPROT, R. - Moi University
|SHAFF, J. - Cornell University
|GUDO, S. - Moi University
|WERE, B. - Moi University
|MAGALHAES, J. - Embrapa
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2013
Publication Date: 1/7/2014
Citation: Matonyei, T., Cheprot, R., Liu, J., Pineros, M., Shaff, J., Gudo, S., Were, B., Magalhaes, J., Kochian, L.V. 2014. Physiological and molecular analysis of selected Kenyan maize lines for aluminum tolerance. Plant Journal. 377:357-367.
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. In this study we screened a large number of maize lines adapted for agriculture in Kenya, to determine if locally adapted Kenyan germplasm harbors significant levels of Al tolerance to use in Kenyan breeding programs. From the project, a number of very Al tolerant maize lines were identified for use in future breeding programs. One of the most tolerant lines does not exhibit high expression of the maize Al tolerance gene we recently identified, and appears to employ novel genes for its tolerance to toxic Al on acid soils.
Technical Abstract: Aluminum (Al) toxicity is an important limitation to maize production in many tropical and sub-tropical acid soil areas. The aim of this study was to survey the variation in Al tolerance in a panel of maize lines adapted for Kenya and look for novel sources of Al tolerance. 112 Kenyan maize accessions were phenotyped for Al tolerance in solution culture. Several Al tolerance-related parameters including relative net root growth (RNRG), root apex Al accumulation, Al-activated root organic acid exudation, and expression of the maize Al tolerance gene, ZmMATE1, were used to classify Kenyan maize accessions. Based on RNRG, 42%, 28%, and 30% of the lines were classified as highly tolerant, moderately tolerant and sensitive, respectively. Tolerant accessions accumulated less Al in their root apices compared to sensitive lines. The Kenyan maize line, CON 5, and the Brazilian standard for tolerance, Cateto, exhibited the greatest Al tolerance based on RNRG, but CON 5 had only about 50% of ZmMATE1 gene expression relative to Cateto. CON 5 also had low root apex Al content and high citrate exudation, suggesting that it may employ a citrate transporter other than ZmMATE1. We identified a very Al tolerant Kenyan maize line whose Al tolerance may be based in part on a novel tolerance gene. The maize lines identified in this study are useful germplasm for the development of varieties suitable for agriculture on acid soils in Kenya.