Development of simple in-vitro protocol for screening low soil nitrogen-efficient maize lines

In order to fast track and compliment conventional maize breeding programme designed for low nitrogen (N) environments, seeds of eight low soil N-tolerant maize lines were sown in the field under no nitrogen and 40 kgN/ha for in vivo evaluation with a view to develop simple protocols for screening maize lines for low nitrogen-efficient through tissue culture technique. Maize plants used for tissue culture (in vitro) were selfed, cobs were harvested fourteen days after pollination before the kernels were disinfected. The immature embryos were excised and cultured on modified Murashige and Skoog basal medium (MS) containing 100% Nitrogen (1650 mg/l), 50% Nitrogen (825 mg/l), 25% Nitrogen (412.5 mg/l), 0% Nitrogen of normal ammonium nitrate in MS salt formulation. Results obtained revealed three lines (LNTP-YC6, TZPB Prol C3 and SW5-OB-BPR-1) had higher grain yield than other maize lines under no fertilizer (0 kgN/ha) and 40 kgN/ha fertilizer applications (P = 0.01) while two lines (TZPB Prol C3 and LAPOSTA SEQUIA C6) performed better than others with or without ammonium nitrate under in-vitro condition (P = 0.01). TZPB Prol C3 was consistent in both in-vitro and in-vivo conditions. Also, MS medium without ammonium nitrate appeared to be more suitable for screening for low N-tolerant maize genotypes.