Identification of QTL for early vigor and leaf senescence across two tropical maize doubled haploid populations under nitrogen deficient conditions

Beside drought, nitrogen deficiency (LN) is the most important factor limiting grain yield (GY) in tropical maize. To understand the genes involved in the response to nitrogen deficiency more thoroughly, two unrelated bi-parental double haploid populations (DHpop1 and DHpop2) were evaluated under LN in a total of four season-by-location combinations. The anthesis silking interval, the normalized differential vegetative index (NDVI), senescence (SEN) and a trait combining information on NDVI, plant height and SEN (Combo) showed a strong association with GY, indicating the suitability of these secondary traits to improve indirect selection for GY under LN. A total of five candidate genes associated with chlorophyll fluorescence (pet1, hcf102 and spt2), SEN (sweet15a) and sugar metabolism (CBF3) were detected in bins 2.07, 4.05 and 8.05. A QTL for SEN was detected in bin 4.05 in both populations. Sweet15a and/or spt2 affecting chlorophyll content, auxin levels and SEN are candidate genes at this locus. Best testcrosses outperformed checks by 15.5–54.4% making them interesting for the use as donors for tolerance to LN.