Using line x tester interaction for the formation of yellow maize synthetics tolerant to acid soils

Breeders need more information on selecting testers to identify fines for formation of synthetics and need more user-friendly methods to study general combining ability (GCA) and specific combining ability (SCA) of genotypes. Forty-three lines were crossed to two narrow-based ($3 line and S3 x S3 hybrid) and two broad-based testers, which were open-pollinated varieties (OPVs). Topcrosses (line x tester, L x T) were evaluated in eight acid soil environments. The additive main effect and multiplirative interaction (AMMI) and the site regression (SREG) models were used to study the GCA of the testers and fines and the SCA of the L x T interaction. The SREG biplot conlains the effect of the lines plus the L x T interaction and displays both GCA and SCA, whereas the AMMI biplot contains the effect of the L x T interaction and displays only the SCA. One synthetic was developed by recombining six lines identified as superior by each tester. The four synthetics were evaluated in 12 acid and nine nonacid soil environments. The synthetic developed with the S3 line as tester yielded the highest and the one developed with an OPV as tester yielded the lowest. The AMMI and SREG models seem to provide an effective tool to visualize and study GCA and SCA of genotypes.
MAIZE is planted on 140 million hectares worldwide, of which 97 million hectares are in developing countries. The area planted with OPVs in developing countries is 54 million hectares, and [...]