A new locus in the r-tl region of linkage group V

Swiecicki, W.K.

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)

Cross

Locus

Phenotype

Total

Chi-sq. (3:1)

D

R
K. 1468 Nlb 88 27 115 0.14
K. 1463 Nlb 66 27 93 0.80
K. 1462 Nlb 90 24 114 0.95
K. 1465 Nlb 88 27 115 0.14
K. 1469 Nlb 82 32 114 0.57
K. 1468 Tl 86 29 115 0.00
K. 1468 Acp1a 79 34 113 1.56
K. 1462 Creep 84 30 114 0.10
K. 1648 Nlb 501 146 647 2.04
K. 1467     124 27 151 4.08*
K.1881    309 103 412 0.00
K. 1648 R 514 160 674 0.57
K. 1467   119 55 174 4.05*
K. 1881   326 98 424 0.80
K. 1648 Tl 498 149 647 1.34
K. 1467   111 56 167 6.48*
K. 1881   316 95 411 0.78
K. 1467 Coch 124 43 167 0.05
K. 1881   313 101 414 0.08

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.

____________________________________________________________________

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.