Swiecicki, W.K., Wolko, B.                                                                     Institute of Plant Genetics
and Kruszka, K.                                                                                       Polish Academy of Sciences
                                                                                               Strzeszynska 34, 60-479 Poznan, Poland

Sharma (1) selected a new mutation type in pea, cabbage leaf, in the M₂ generation after dry seed treatment of the initial line Large Podded G-20 by DES and NMU. A monogenic recessive mode of inheritance was found and the gene symbol calf was proposed. The calf mutation had a pleiotropic effect on leaves, stipules, stem, flowers and pods (all enlarged) and the plants were fully sterile (abnormal flowers, enlarged and curved pods, sometimes developing seeds without embryos). This mutation was maintained through heterozygous plants and included in Pisum gene banks at the Weibullsholm Plant Breeding Institute, Sweden (catalogue number WL5873) and at the Plant Breeding Station Wiatrowo, Poland (catalogue number Wt15873).

In experiments on induced mutations in pea at Wiatrowo (Poznan Plant Breeders), a mutation of the cabbage leaf type was selected after irradiation of dry seeds of cv. Pegro (Wt6048) by Nf, and included in the Pisum gene bank with catalogue number Wt16024. The locus identity test (made by crossing heterozygous plants) showed that both mutants were allelic. Lines Wt15873 and Wt16024 are considered as the type lines for mutant alleles calf-1 and calf-2, respectively.

Line Wt16024 was used in linkage studies at Wiatrowo due to the availability of its initial line (Wt6048). Several testerlines were crossed to line Wt16024 and the F₂ generations were analysed for linkages. Joint segregation Chi-squares were obtained using a 2 ґ 2 contingency table and recombination values were estimated using the product-ratio method. Linkage groups are numbered in accordance with Weeden et al. (2).

No linkage was observed with gene markers from groups IA (a), IB (d, i), III (M, st, b), IVA (n, fa), IVB (v) and V (r, tl, coch, gp, te, cp, creep, ce, U^st, Fs). A deviation from independent assortment (P < 0.01) was observed for the gene pair Calf and Wb in cross Wt16024 ґ Wt11238 (Table 2). Based on this evidence, two lines, Wt10659 and Wt11685, with group II isozymic markers Pgm-p and Fum were used for crosses. Monogenic segregation ( with P > 0.02 ) was found for calf and all markers (Table 1). Both crosses

 Table 1. Monohybrid segregation for calf and group II markers observed in F₂ populations of the following crosses: 1) Wt16024 ґ Wt11238; 2) Wt16024 ґ Wt10659; 3) Wt16024 ґ Wt11685.

^a D, dominant; R, recessive; S, homozygous slow; H, heterozygous slow/fast; F, homozygous fast.

Table 2. Dihybrid segregation data for calf and group II markers wb, Fum and Pgm-p obtained from the F₂ of the following crosses: 1) Wt16024 (calf Wb Pgm-p/F Fum/S) ґ Wt11238; 2) Wt16024 ґ Wt10659; 3) Wt16024 ґ Wt11685.

^a D, dominant; R, recessive. In the case of isozyme markers the D class includes the heterozygotes and either the slow or fast class as required to bring the cross into coupling phase.

provided evidence of significant (P < 0.0001) linkage between calf and Fum with a distance of 17 cM (Table 2). The cross with Wt11685 revealed close linkage between calf and Pgm-p with a distance of 2 cM.

In summary, the data in Table 2 provide convincing evidence that the calf locus is in the vicinity of locus Pgm-p in linkage group II and indicate a probable map sequence of wb...19...calf...2...Pgm-p...15...Fum.

^{_______________}

1. Sharma, B. 1975. Pisum Newsletter 7:53.

2. Weeden, N.F., Swiecicki, W.K., Timmerman-Vaughan, G.M., Ellis, T.H.N. and Ambrose, M. 1996.
     Pisum Genetics 28:1-4.