Institute of Plant Genetics
Polish Academy of Sciences
Strzeszynska 34, 60-479 Poznan, Poland

The narrow leaflet base mutation (nlb, mutation 122) was induced and selected by Gottschalk in cv. Dippes Gelbe Viktoria after treatment of dry seed with 7 krad of X-radiation (1,2). The mutant was included in Pisum collections at the Weibullsholm Plant Breeding Institute (renamed the Nordic Gene Bank), the Plant Breeding Station in Wiatrowo in 1979 (respective catalogue numbers: Wl 6116 and Wt 15878), and later the John Innes Institute (JI 2986). The name of the mutant reflects the altered phenotype, and identification of this mutant phenotype in segregating populations is relatively easy, particularly on young plants before flowering.

The linkage project for the nlb gene included the following lines from the collection at Wiatrowo: Wt 11143, Wt 11238, Wt 11288, Wt 11538, Wt 11540, Wt 11777, and Wt 15860. The following markers were observed in segregating F2 plant populations: d, Idh, i (linkage group I), a, Est3, Pgmp, k, wb, s (linkage group II), Lap1, b, st, M, Dia1 (linkage group III), n, Alatp, v (linkage group IV), Fs, U, ce, Pgdc, creep, Acp1, cp, te, gp, tl, r, coch (linkage group V), Pl, Arg, wlo, art2, (linkage group VI), and Gal2, Aldo, Aatm, Est1, Est2, Pgdp, Pgmc, (linkage group VII). Crosses between the mutant line and tester lines were done in 1993, 1994, 1995 and 1996. Gene segregations were observed in field and in greenhouse in 1995, 1996, 1997 and 1998.

In F2 populations a monohybrid segregation of the mutant character was observed (Table 1). These results confirm the existence of the gene and identify mutant 122 as the type line (under different catalogue numbers in three gene banks, mentioned above). Dihybrid segregation analysis for pairs nlb with markers mentioned above did not show deviations for markers on linkage groups I, II, III, IV, VI or VII. Disturbed dihybrid segregation for the gene pair nlb-tl suggested that nlb was located on linkage group V (Table 2, cross K.1468). Additionally, undisturbed dihybrid segregation between nlb and Acp1 (cross K.1468) and between nlb and creep (cross K.1462) suggested that nlb was not located in a lower part of that linkage group.

Table 1. Monohybrid segregation K. 1468 = Wt 15878 (nlb) x Wt 11538 (tl, Acp1-s)

^afor Acp1 3:1 segregation fast variants were added to heterozygotes
*P < 0.05

 

Table 2. Joint segregation analysis for loci on linkage group V

Cross	Loci	Phenotype					Joint c2	Recomb.Fraction	SE	Phase
		DD	DR	RD	RR	Total
K. 1468	Nlb/Tl	59	29	27	1	115	11.9	18.6	8.9	R
K. 1468	Nlb/Acp-1	65	23	20	7	115	0.00	49.8	7.0	R
K. 1462	Nlb/Creep	65	25	19	5	114	0.47	44.6	7.4	R
K. 1648	Nlb - R	349	152	144	2	647	52.3	12.4	3.8	R
K. 1467		80	44	26	1	151	10.7	18.0	7.8	R
K. 1881		215	94	103	1	412	40.5	10.4	4.9	R
K. 1648	Nlb - Tl	353	148	145	1	647	53.1	9.0	3.9	R
K. 1467		75	49	27	1	151	15.8	16.3	7.9	R
K. 1881		212	95	103	1	410	41.8	10.3	4.9	R
K. 1648	R-Tl	481	12	17	137	674	496	4.6	0.8	C
K. 1467		106	11	5	45	167	102	8.6	2.3	C
K. 1881		314	3	2	92	411	378	1.2	0.5	C
K. 1467	Nlb -Coch	88	36	26	1	151	7.7	20.6	7.7	R
K. 1881		216	93	95	8	412	20.3	28.2	4.5	R
K. 1467	R - Coch	98	19	26	24	167	18.5	29.8	4.4	C
K. 1881		271	42	49	52	414	62.7	26.0	2.6	C
K. 1467	Coch - Tl	99	25	12	31	167	38.6	22.1	3.7	C
K. 1881		269	42	47	53	411	67.1	25.4	2.6	C

Three, additional crosses were done with markers localized above the Gp locus: K.1648 (nlb x r, tl), K.1467 (nlb x r, tl, coch) and K.1881 (nlb x coch-het, r, tl) (Table 2). The results confirmed that nlb is localized in this region of the linkage group V. Clear-cut results were obtained from an analysis of the cross, K.1648, in which 647 F2 plants segregating at Nlb, R, and Tl. Strong deviations from dihybrid segregation and linkages were noted for Nlb – Tl (Cr-O = 9.0) as well as for Nlb – R (Cr-O = 12.4). In the next cross, K.1467 an additional gene marker (coch) segregated. Linkages between Nlb – Tl and Nlb – R were confirmed, but the relatively undisturbed dihybrid segregation between Nlb and Coch (joint Chi-square = 7.7) suggested that the Nlb locus lies above the Tl – R segment.

In the third cross, K.1881 (424 F2 plants, analyzed in 1998) the coch-het allele was used instead of coch because of its lack of effect on flower structure (see reference 3). This allele segregated normally (Table 1). Joint segregation analysis confirmed that Nlb is linked to Tl (Cr-O = ± 10) and is positioned toward the end of the linkage group.

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1. Gottschalk, W. 1964. Die Wirkung Mutierter Gene auf die Morphologie und Funktion Pflanzlicher Organe. G. Fisher Verlag, Jena.
2. Gottschalk, W., and Hussein H.A.S. 1976. Egypt. J. Genet. and Cytol., 5: 312-330.
3. Swiecicki, W.K., 1990. Pisum Newsl. 22: 62-63.