Physiological and molecular analysis of aluminum tolerance in selected Kenyan maize lines
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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.
KeywordsAluminum toxicity Aluminum tolerance Root apex aluminum concentration Root citrate exudation
The authors wishes to acknowledge the Generation Challenge Program (GCP) and McKnight Foundation for funding, Moi University for facilities and technical support, the USDA-ARS Robert Holley Center for Agriculture and Health for the mentoring of the first author and the provision of laboratory and technical support. We also wish to thank Drs. Lyza Maron and Michael Rutzke for their technical expertise and to Eric Craft for having worked tirelessly to ensure all the resources were available for use in the testing laboratory. Special thanks go to KARI–Kitale for providing some of the seed for Kenyan accessions.
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