COMBINING ABILITY EFFECTS FOR P-EFFICIENCY CHARACTERS IN MAIZE CROWN IN LOW-P NUTRIENT SOLUTION

This study aimed at obtaining preliminary information on gene effects of P-efficiency traits in maize grown under low-P concentration nutrie nt solution, using genotypes from a diallel mating system. An experime nt with 36 entries (eight parental lines and 28 single crosses) was co nducted in the greenhouse, at the Experimental Center of Campinas, Ins titute Agronomico (IAC), State of Sao Paulo, Brazil. Young plants (26 days of age) were evaluated for the P-efficiency characteristics, usin g a randomized complete block design with five replications. The gener al combining ability (GCA) and specific combining ability (SCA) inform ation on crosses were obtained by using the method 4, model I analysis of Griffing, for the variables: total (whole plant) dry matter (Tdm), root dry matter (Rdm), total P content in the plant (Total-P) and the P-use efficiency index (EI). In the average, the higher GCA estimates for Tdm, Total-P and EI were obtained for the inbred L39, evidencing the positive contribution of this parental to enhance these characters in their Fl hybrids. For the Rdm character, the major contribution ca me from L42. The most expressive estimates of SCA for the characters T dm, Rdm and EI were detected for the crosses L42xL29, L40xL34, and L11 xL39; and, for Total-P, were the crosses L40xL34, L11xL39 and L39xL42. L39 and L42 may be considered promissor inbred lines in maize breedin g programs aimed at selecting and improving more efficient maize genot ypes under low P conditions. The characters related to P-efficiency in maize seedlings grown in low P nutrient solution were mainly controll ed by additive effects, although the non-additive effects have also sh own to be important. In a breeding program, plant selection in low-P n utrient solution may be useful and successful when a large number of p lants are tb be evaluated and when cycles of selection are alternated with field evaluations.