Mapping Heterotic Loci for Yield and Agronomic Traits Using Chromosome Segment Introgression Lines in Cotton

In the present study, a set of chromosome segment introgression lines （CSILs） using Gossypium hirsutum L. TM-1 as the recipient parent and G. barbadense Hai7124 as the donor parent were used to explore the genetic basis of heterosis for interspecific hybrids. Two sets of F1 populations individually derived from CSILs crossing with both parents were configured to investigate heterotic loci （HL） and substitution effect loci （SL）. A total of 58 HL and 39 SL were identified in 3 years. One stable HL, hLP-A4-3, could be detected in all 3 years. Three HLs, hBS-A8-1, hLP-D6-1, and hSI-D7-11, could be detected in 2 years. Four SLs, sBSoD7- 1, sLP-A8-1, sLP-D7-1, and sLP-D12-1, could be detected in 2 years. HL and SL tended to be distributed in some HL-rich chromosome segments with close positions. Compared with QTL detected in a former study, HL showed little overlap with QTL, indicating that trait phenotype and heterosis might be controlled by different sets of loci. All three forms of genetic effects （partial-, full-, over-dominant） were identified, while the over-dominant effect made the main contribution to heterosis. These results may help lay the foundation for clarifying the heredity mechanism of heterosis in cotton.

Development, identification and utilization of introgression lines using Chinese endemic and synthetic wheat as donors

Chromosome segmental introgression lines（ILs）are an effective way to utilize germplasm resources in crops.To improve agronomic traits of wheat cultivar（Triticum aestivum） Shi 4185, four sets of ILs were developed. The donors were Chinese endemic subspecies accessions Yunnan wheat（T. aestivum ssp. yunnanense） YN3, Tibetan semiwild wheat（T. aestivum ssp. tibetanum） XZ-ZM19450, and Xinjiang wheat（T. aestivum ssp. petropavlovskyi） XJ5, and synthetic wheat HC-XM1620 derived from a cross between T. durum acc. D67.2/P66.270 with Aegilops tauschii acc. 218.Totals of 356, 366, 445 and 457 simple sequence repeat（SSR）markers were polymorphic between Shi 4185 and YN3, XZZM19450, XJ5 and HC-XM1620, respectively. In total, 991 ILs were identified, including 300 derived from YN3, covering 95%of the genome of Shi 4185, 218 from XZ-ZM19450（79%）, 279 from XJ5（97%）, and 194 from HC-ZX1620（84%）. The sizes and locations of each introgression were determined from a consensus SSR linkage map. Using the ILs, 11 putative Resear quantitative trait loci（QTLs） were identified for plant height（PH）, spike length（SL） and grain number per spike（GNS）.Comparative analyses of 24 elite ILs with the parents revealed that the four donor parents could be important resources to improve wheat SL and GNS. Our work offers a case for utilizing endemic landraces for QTL mapping and improvement of wheat cultivars using introgression lines.