Identification and QTLs Validation for Aluminum Tolerance in Maize

Al toxicity is one of the major constrictive factors of plant root growth in acid soils, leading to limitations in crop production. These soils are present in close to 50% of global arable land. In species such as sorghum, barley and Arabidopsis Al tolerance is due to action of genes that encodes transporters of organic acids. However, only organic acids exudation is not enough to explain Al tolerance in maize. In this study, we used the Relative Net Root Growth (RNRG) in nutrient solution with 39 µM of Al activity after five days as a phenotypic index for Al tolerance. QTL mapping was performed in 118 RILs from a cross between Cateto 237/67 (Al tolerant) and L53 (Al sensitive). The genetic linkage map was composed by 1200 molecular markers, including 204 SSR markers, 994 SNPs and candidate genes ZmMATE1 and ZmMATE2. Seven Al tolerance QTLs were mapped on maize chromosomes 3, 5, 6 and 8, explaining over 63% of the phenotype variation. The expression of ZmMATE1 and ZmMATE2 genes were also mapped in the population. One of the major Al tolerance QTL located at chromosome 6 was co-localized with the ZmMATE1 and with the expression of ZmMATE1. This QTL was responsible to improve Al tolerance in near isogenic lines (NIL). ZmMATE2 was co-localized with the second major QTL on chromosome 5, while its eQTL was mapped on chromosome 3. Indeed this QTL was not validated in NILs. Thus, the QTL6 can be used in breeding programs to improve Al tolerance in maize.

Financial support: CNPq, Fapemig, CAPES, Embrapa, ISF, McKnight, GCP.