PISUM Genetics                                                   2003Volume 35                                            Research Papers
A new gene for supernodulation in pea: nod6
Sidorova, K.K., Shumny, V.K.,                                           Inst. of Cytology and Gen., Russian Acad. of Sci.
Mischenko, T.M. and Vlasova, E.Yu                                                                              Novosibirsk, Russia
Five supernodulating mutants, K10a, K11a, K12a, K21a and K22a, have been induced from Rondo by treatment of seeds with EMS. The morphological and symbiotic properties were described previously [1]. K10a, K11a, and K12a are allelic to one another and to the nod3 mutant. K21a and K22a are monogenic recessive mutations eliciting pleiotropic effects. Additionally, they have a short stem and short lateral roots. Monohybrid segregation was observed following crosses with the original variety (Table 1). K21a and K22a are allelic to each other, but not to the nod3 mutant or the supernodulating K301a (nod4) mutant induced from Ramonsky 77 [2].
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Reciprocal grafting of nod6 shoots on original Rondo stocks and vice versa suggests that nodulation in K21a and K22a is controlled by the stem, whereas in KlOa, K11a, and K12a nodulation is determined by the root. It has been concluded that K21a and K22a are mutations at a different locus, which is associated with supernodulation. We designated this mutation nod6.
Chromosomal localization of the nod6 gene was performed using tester lines 851 and 1238, and the sym11 mutant (sym11 seeds were courtesy of Prof. N.F. Weeden). No linkage was found between nod6 and any of the marker genes by crossing K22a to 1238 plants. Linkage was detected between nod6 and oh and sym11, both located on chromosome 4 (linkage group VII), by crossing K22a to 851 and sym11 plants [3].
Monohybrid segregation for the nod6 gene and the marker oh and sym11 genes was observed in populations F2 nod6 X 851 and F2 nod6 X sym11 (Table 2).
Table 2. Segregation for the nod6 gene and the marker oh and sym11 genes in populations F2 nod6 X 851 and F2 nod6 x syml l.
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It has been established that the new gene, nod6, which controls supernodulation in pea, is located on chromosome 4 (linkage group VII) 35.6 cM away from the oh gene and 27.4 cM away from the sym11 gene. Gene mapping of nod6 is consistent with chromosome mapping [3].
Recombination frequencies between nod6 and the oh and sym11 genes are presented in Table 3.
Table 3. Joint segregation data for the loci nod6, oh and symll on linkage group VII obtained in F2 of the cross K22a X L851 and K22a X symll.
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1. Sidorova, K.K., Vlasova, E.Yu., Mischenko, T.M., Glianenko, M.N. and Shumny, V.K. 1999. Pisum Genetics 31: 34.
2.    Sidorova, K.K. and Uzhintseva L.P. 1995. Pisum Genetics 27: 21.
3.    Weeden, N.F., Ellis, T.H.N., Timmerman-Vaughan, G.M., Swiecicki, W.K., Rozov, S.M. and Berdnikov, V.A. 1998. Pisum Genetics 30: 1-4.