Inheritance of Blue Grain Colour and Its Association with J and Js Translocation Chromosomes in Wheat-Agrotana Hybrid Lines

Genomic in situ hybridization (GISH) using S genomic DNA as a probe was applied to study inheritance of blue seed color and characterize the chromosome constitution of blue-grained lines selected from derivatives of Chinese Spring (CS)×Agrotana, a multiple disease resistant wheat-Th. ponticum partial amphiploid line. The results showed that the expression of blue seed color in the CS-Agrotana advanced hybrid lines was always linked with a pair of translocation chromosomes derived from J and Js genomes of Th. ponticum. The blue-grained lines had 43–44 chromosomes, which included 2 J-Js+2 (or 1) Js-J alien translocation chromosomes, while the red-grained lines had 41–42 chromosomes, only carried 2 J-Js translocation chromosomes. This suggested that the Js-J translocation chromosomes might carry the major gene(s) that controlled the blue grain color. Since the J-Js translocation chromosomes were always present with the Js-J translocation chromosomes in blue-grained lines, it is possible that the blue grain color resulted from an interaction between the 2 translocations. Meiotic analyses of chromosome pairing in the blue-grained lines indicated that the 2 pairs of the alien translocation chromosomes did not pair each other, nor did they pair with the wheat chromosomes. The occurrence of 2 bivalents and no alien quadrivalents in the blue-grained lines with Js-J and J-Js translocation chromosomes, demonstrated that the 2 alien chromosome translocations were not reciprocal translocations. The J-Js translocation chromosomes present in the blue-grained lines were more stable at meiosis than the Js-J translocation chromosomes. The Js-J chromosomes were easily lost, resulting in an instability in grain color that could change from light blue to red. Our results determined the molecular cytogenetic characteristics and inheritance of the alien translocation chromosomes present in the blue-grained lines carrying resistance genes to common root rot. This study further confirmed that the chromosome translocations among the Js and J genome were responsible for blue grain color.