Screening and evaluating low nitrogen tolerant wheat genotype at seedling stage

Nitrogen tops the list of crop macro elements essential for plant growth and development. Several studies have shown that under low nitrogen conditions, crop species/genotypes vary widely in nitrogen uptake ability and utilization efficiency. Planting wheat cultivars with high nitrogen efficiency is the fundamental way to raise nitrogen utilization efficiency; and exploiting nitrogen tolerant wheat germplasm resources is the basic of breeding wheat varieties with high nitrogen efficiency. To this end, 30 advanced distant hybridization lines of wheat and wheatgrass, one T1BL·1RS translocation line of distant hybridization of "Xiaoyan 6" and "Germany white" (rye), two recombinant inbred lines of "Xiaoyan54 × Jing411" and 13 commercial wheat varieties, were screened and evaluated for low nitrogen tolerant genotypes in hydroponic culture at seedling stage. Analysis of variance showed significant to very significant differences in 13 nitrogen efficiency related traits between two nitrogen treatments and among genotypes. Principal component analysis showed that the first three principal components had an accumulative contribution rate of at least 81.2%, implying that they contained most of the information to reflect the overall trait resources. The proportions of relative shoot/plant nitrogen uptake, root/shoot ratio, shoot dry weight, plant dry weight, shoot nitrogen utilization efficiency and root nitrogen content of the three principal components were significantly high. A comprehensive evaluation suggested that 08B41 had the highest score (1.60) for the best nitrogen tolerant wheat line in the 32 distant wheat hybridization lines. Then "Kn9204" had the highest score (2.10) for the best nitrogen tolerant wheat variety in the 13 commercial wheat varieties. Clustering analysis showed that the 46 wheat genotypes were broadly categorized into 3 groups (low nitrogen tolerant type, medium nitrogen tolerant type and low nitrogen sensitive type with 15, 22 and 9 genotypes, respectively). 9 advanced distant hybridization lines (08B41, XJ19-1, 08B8, 08B10, 08B13, 08B25, WR9603, 08B2, 08B5) and 6 commercial wheat varieties ("Kn9204", "Han7086", "Henong827", "Shimai18", "Shi4185", "Shixin733") were noted to have low nitrogen tolerance. These low nitrogen tolerant genotypes were utilizable in breeding N-efficient wheat varieties. The study also discussed the roles of wheat related species in improving the genetic makeup of N-efficient wheat varieties.