Preliminary Phenotypic and SNP-Based Molecular Characterization of Maize (<i>Zea mays</i>L.)-Mexicana (<i>Zea mays</i>SSP. <i>Mexicana</i>) Introgression Lines under Inbred Background of 48-2

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.