Development of Near Isogenic Lines of Wheat Carrying Different Spike Branching Genes and Their Agronomic and Spike Characters

The branched spike introduced from T. turgidum in common wheat was controlled by two recessive genes (sb1 and sb2). The effect of specific sb on the development and spike characters can be accurately determined by using isogenic lines (NILs), which, however, were not usually available. In this study, four genotypes having different combinations of the two sb genes with a common genetic background cv. Taishan were produced by continuous backcrossing and determined by crossing and test-crossing. The four NILs included one line with branched spike, DR (sb1sb1 sb2sb2), and three lines with normal spike, SR1 (sb1sb1 Sb2Sb2), SR2 (Sb1Sb1 sb2sb2), and DD (Sb1Sb1 Sb2Sb2). These NILs were grown during two growing seasons (2008–2009 and 2009–2010) to investigate the effects of sb genes on agronomic and spike characters. The results showed that SR1 postponed significantly the days to heading and the days to anthesis, and SR2 decreased significantly grain number by reducing the fertile floret in a spike. DR not only displayed the branched spike but also had great effects on agronomic and spike characters. In DR, the days to maturate was significantly postponed, and the number of fertile floret and grain number increased in a spike, but the grain set reduced significantly. This indicated the sb combinations have different effects on the agronomic and spike characters. This research made foundation for analyses of mechanisms of branched spike formation and associated properties in hexaploid wheat in future.