Nitrogen (N) plays a vital role in the productivity of maize (Zea mays L). To investigate the fertilizer effects of N on the yield and growth of maize hybrid variety (Gorilla), the experiment was carried out at the research farm of University of Swabi, Pakistan, during summer 2017-18. Four levels of N (Urea, Urea + Farm Yard Manure (FYM), Urea + Compost, Urea + Poultry Manure (PM)) were set in the present study. Randomized complete block design (RCBD) was used with split-plot arrangement with N administering to main plot. Results showed that yield and other traits, i.e. plant height, ear length, ear weight, kernel yield, kernels ear −1 and harvest index (HI) were significantly affected by Nitrogen. In current study, the maximum performances of plant height (231.46 cm), ear length (12.17 cm), kernels ear −1 (434.83), kernel yield (2095.7 kg•ha −1 ), total kernel weight (350.75 kg•ha −1 ), biomass yield (4015.3 kg•ha −1 ) and HI (37.31) were recorded under the treatment of UREA + PM, and followed by UREA + FYM. Besides, the applications of organic manure in combination with nitrogen significantly increased yield and its components. Application of 50% of N and 50% of poultry manure produced higher performance for the traits of plant height, ear length, kernels ear −1 , total kernels weight ear −1 , kernel yield, and biomass yield.

Wild relatives possess potential genetic diversity for maize (Zea mays L.) improvement. Characterization of maize-mexicana introgression lines (ILs) is of great value to diversify the genetic base and improve the maize germplasm.Four maize-mexicana IL generations, i.e. BC1, BC2, BC3, and RIL, were constructed under the elite inbred background of 48-2, elite inbred line that is widely used in maize breeding in Southwestern China, and were phenotyped in different years and genotyped with 56110 SNPs. The results indicated that 48-2 had higher phenotypic performances than all the characterized ILs on most of the agronomic traits. Compared with other ILs, BC2 individuals exhibited more similar performance to 48-2 on most traits and possessed the highest kernel ratio (66.5%). Population structure and principal component analysis indicated that BC3 individuals gathered closer to 48-2 and exhibited the lowest mexicana-introgression frequency (0.50%), while BC2 (29.06%) and RIL (18.52%) showed higher introgression frequency. The high level of genetic diversity observed in the maize-mexicana ILs demonstrated that Z. mays ssp. mexicana can serve as a potential source for the enrichment of maize germplasm.

Kernel size-related traits, including kernel length, kernel width, and kernel thickness, are critical components in determining yield and kernel quality in maize (Zea mays L.). Dissecting the phenotypic characteristics of these traits, and discovering the candidate chromosomal regions for these traits, are of potential importance for maize yield and quality improvement. In this study, a total of 139 F2:3 family lines derived from EHel and B73, a distinct line with extremely low ear height (EHel), was used for phenotyping and QTL mapping of three kernel sizerelated traits, including 10-kernel length (KL), 10-kernel width (KWid), and 10-kernel thickness (KT). The results showed that only one QTL for KWid, i.e., qKWid9 on Chr9, with a phenotypic variation explained (PVE) of 13.4% was detected between SNPs of AX-86298371 and AX-86298372, while no QTLs were detected for KL and KT across all 10 chromosomes. Four bulked groups of family lines, i.e., Groups I to IV, were constructed with F2:3 family lines according to the phenotypic comparisons of KWid between EHel and B73. Among these four groups, Group I possessed a significantly lower KWid than EHel (P = 0.0455), Group II was similar to EHel (P = 0.34), while both Group III and Group IV were statistically higher than EHel (P < 0.05). Besides, except Group IV exhibited a similar KWid to B73 (P = 0.11), KWid of Groups I to III were statistically lower than B73 (P < 0.00). By comparing the bulked genotypes of the four groups to EHel and B73, a stable chromosomal region on Chr9 between SNPs of AX-86298372 to AX-86263154, entirely covered by qKWid9, was identified to link KWid with the positive allele of increasing phenotypic effect to KWid from B73, similar to that of qKWid9. A large amount of enzyme activity and macromolecule binding-related genes were annotated within this chromosomal region, suggesting qKWid9 as a potential QTL for KWid in maize. KEYWORDSMaize (Zea mays L.); kernel size-related traits; QTL mapping; bulked sample analysis (BSA)