Confirmation that the sn locus is between Aldo and Gal2 in linkage group VII of pea

Pisum Genetics Volume 28 1996 Research Reports 13

Murfet, I.C. Department of Plant Science, University of Tasmania

and Sherriff, L.J. Hobart, Tas 7001, Australia

Sn is one of three complementary dominant genes Sn, Dne and Ppd which together confer the ability to respond to photoperiod and a late flowering habit in pea (1-4). The recessive mutant allele sn causes a loss of the photoperiod response, and common early flowering, day neutral cultivars such as Sparkle, Massey, Alaska and Progress #9 are homozygous for this allele (2, 5, 7). Weeden et al. (7) reported very close linkage between sn and the amylase locus Amyl leading to placement of the sn locus between isozyme loci Aldo and Gal2 in the lower section of linkage group VII in recent maps (e.g. 8).

We have recently obtained data from cross HL249 (Aldo^S Sn Gal2^S) x Sparkle (Aldo^Fsn Gal2^F) which confirm that location. Monohybrid segregation for Aldo and sn was in good accordance with expectation (P>0.5), but segregation for Gal2 was mildly disturbed (P<0.01). The dihybrid segregation data (Table 1) indicate linkage between all markers and generate the following map:

These results are in reasonable accordance with, and thus support, the 1993 (8) and current (9) maps for this section of the pea genome. Whether sn is located above or below Amyl remains undetermined.

Table 1. Dihybrid segregation data from the F₂ of the cross HL249 (Aldo^S Sn Gal2^S) x Sparkle (Aldo^Fsn Gal2^F). The plants were grown under an 8-h photoperiod to allow unequivocal recognition of Sn and sn segregants. The data were analysed using the program LINKAGE1 (6).

¹D = dominant, R = recessive, F = homozygous fast, H = heterozygous, and S = homozygous slow. The first named

locus is shown first.

*, ** P<0.05 and 0.0001, respectively.

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1. Arumingtyas, E.L. and Murfet, I.C. 1994. J. Hered. 85:12-17.

2. Barber, H.N. 1959. Heredity 13:33-60.

3. King, W.M. and Murfet, I.C. 1985. Ann. Bot. 56:835-846.