TY  - PRO
AU  - Lagarda Murrieta,R.
AU  - Edmeades,G.O.
AU  - Edmeades,G.O.|Banziger,M.|Mickelson,H.R.|Peña-Valdivia,C.B.
AU  - Banziger,M.
ED  - Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Mexico DF (Mexico)
TI  - Maize landraces:  Sources of tolerance to low soil nitrogen?
SN  - 968-6923-93-4
U1  - 633.153 
PY  - 1997///
CY  - Mexico, DF (Mexico)
PB  - CIMMYT
KW  - Nitrogen content
KW  - Nutrient uptake
KW  - Selection
KW  - Varieties
KW  - AGROVOC
KW  - Zea mays
KW  - Soil fertility
KW  - Genotypes
KW  - CIMMYT
N2  - A total of 209 tropical maize accessions from the CIMMYT germplasm bank were evaluated over the course of three experiments to identify sources of tolerance to N deficiency. We measured grain yield, plant height and maturity under both high and low soil nitrogen. Under low N we also measured N uptake, N harvest index, ear leaf area, and ear leaf chlorophyll concentration. Maturity and season of evaluation had large effects, so results were analyzed separately for early and late landraces in winter and summer experiments. Landraces could be grouped using cluster analysis. Accessions from certain locations tended to have similar maturities. Some Cuban accessions were characterized by superior performance under low N. We identified 54 accessions with high total N recovery, harvest index, and grain %N, from various regions. These were grouped by maturity and intercrossed to form early and late source populations. After three cycles of intercrossing as half-sibs in a low-N nursery with very slight selection pressure for ear formation and reduced plant height, the populations underwent three additional cycles of improvement with 20-50% selection pressure for yield and plant type under low N. 171 two evaluations where N stress reduced mean yields to 1.05 t ha-1, yields of C6 of the source populations were not significantly less than the yields of improved check varieties. Yield of the early population increased by 15% per cycle between C4 and C6, and that increase was 11% per cycle in the late population. With continued improvement, these source populations may provide valuable traits for low N environments
ER  -