Densinodosum - a new gene on linkage group III

  

Swiecicki, W.K. and Wolko, B.                      Institute of Plant Genetics, Polish Academy of Sciences,

                                                                                          Strzeszynska 34, 60-479 Poznan, Poland

 

       Among numerous mutation types following treatment of dry seeds of Wt 3527 (cv. Paloma) with a combined dose 200 r Nf + 0.014 % NEU the densinodosum mutant gene was  selected in the M2 generation (2). After multiplication the line was included to the Pisum Gene Bank at Wiatrowo with the catalogue number Wt 11242. The name densinodosum is justified by a phenotype­­—mutant plants in comparison to the initial line have shorter stem with a larger number of nodes (Table 1). Number of nodes to the first flower remains unchanged.

  

Table 1. Selected, morphological characters of densinodosum mutant plants and initial line Wt 3527.

Line

 

Stem length (cm)

 

Number of nodes

 

 

Number of nodes

to the 1st flower

 

 

 

 

 

Wt 3527 (Paloma) -initial

41.0

18.2

13.8

Wt 11 242 (dnd – mutant)

33.1

21.5

13.9

 

 

 

 

 

      After multiplication of mutant plants, aspects of dry seed yield were also compared (Fig. 1). It appeared that the densinodosum mutant produced higher yield thanks to a larger number of pods and seeds per plant. Thousand grain weight is smaller.

  

 

Fig. 1. Aspects of dry seed yield of densinodosum mutant plants related to the initial line Wt 3527 = 100%.

      The locus identity test cross for the densinodosum and two genes with a similar phenotype, art1 and art2, was conduced (3). F1 plants of all cross combinations were normal, suggesting that densinodosum (Wt 11242) and arthritic  mutants (Wt 16126 - art1 and Wt16125 - art2) are not allelic.

      For mapping the new mutant gene the line Wt 11242 was crossed with the set of tester lines with markers for seven linkage groups. An analysis of a monohybrid segregation in F2 generations showed Mendelian, recessive nature of the new gene (Table 2.). The symbol dnd is suggested. Undisturbed, monohybrid segregation of most of observed markers was also observed.

 

Table 2. Monohybrid segregation for the investigated gene dnd and gene markers in the linkage group III observed in F2 populations of the following linkage test crosses: K. 1140 = Wt 11242 x Wt 11540; K. 1139 = Wt 11242 x Wt 11538; K. 1137 = Wt 11242 x Wt 11777; K. 1135 = Wt 11242 x Wt 11238; K. 1136 = Wt 11242 x Wt 11288; K. 1864 = Wt 10357 x Wt 11242; K. 1866 = Wt 11242 x Wt 15327; K. 1973 = Wt 11242 x Wt 15298. 

Cross combination

Gene

Allele

Total

Chi square*

(3:1)

dominant

recessive

K. 1140

Dnd

 80

27

107

0.00

K. 1139

Dnd

 80

25

105

0.08

K. 1137

Dnd

 84

19

103

2.36

K. 1135

Dnd

107

36

143

0.00

K. 1136

Dnd

140

50

190

0.18

K. 1864

Dnd

 97

19

116

4.60

K. 1866

Dnd

211

52

263

3.83

K. 1973

Dnd

268

71

339

2.97

K. 1136

B

106

30

136

0.63

 

St

148

47

195

0.08

 

M

 99

39

138

0.78

K. 1864

Uni

 93

25

118

0.92

 

Apu

 87

31

118

0.10

K. 1866

M

 69

22

91

0.03

 

Chi 32

197

64

261

0.03

K.1973

Lum2

285

65

350

7.71

 

M

173

56

229

0.04

  * c2 = 3.84

  

      Observations of plants in F2 generations gave undisturbed dihybrid segregations for gene pairs dnd—gene marker for linkage groups I, II, IV, V, VI and VII. Disturbed, dihybrid segregation was found in the cross combination K. 1136 for dnd-M from linkage group III with Cr-O value 15.8 (Table 3). However, dnd did not show linkage with either b or st in K. 1136 or with unitac or apu in the cross combination K. 1864.

         Two chlorophyll genes–chi32 and lum2–were previously mapped in our laboratory near M on linkage group III (1, 4).  Therefore the type line for dnd was crossed to the lines Wt 15327 (chi32, M) and Wt 15298 (lum2, M). Dnd showed clear linkages with both Lum2 and Chi32, confirming its location in the M-segment. At this stage of mapping studies it is impossible to state on which side of M Dnd is located, although the absence of linkage with Uni suggests that Dnd may be on the opposite side of M from Uni.

Text Box: Table 3. Distribution of phenotypes in F2 populations and the linkage tests for the investigated gene dnd. Joint segregation of gene pairs in the linkage group III (K. 1136 = Wt 11242 x Wt 11288, K. 1864 = Wt 10357 x Wt 11242, K.1866 = Wt 11242 x Wt 15 327, K. 1973 = Wt 11242 x Wt 15298

Cross Combination	Pair of genes	Phase	Phenotype	Total	Joint chi square	Cr-O value + SE (per cent)
			DD	Dr	rD	rr			
									
K. 1136	Dnd - M	C	89	11	10	28	138	53.4	15.8 ±  3.4
	Dnd - B	R	78	21	28	9	136	0.2	52.5 ±  6.2
	Dnd - St	R	104	36	41	9	190	1.2	43.6 ±  5.8
	B - St	C	90	16	12	18	136	25.1	23.9 ±  4.3
	B - M	R	69	35	26	4	134	4.7	33.6  ±  7.6
	St - M	R	68	34	31	5	138	5.0	34.4  ±  7.4
K. 1864	Uni* - Dnd	R	74	18	23	1	116	3.3	27.2  ±  8.5
	Uni - Apu	C	72	21	15	10	118	3.1	38.7 ±   6.0
	Dnd - Apu	R	67	30	18	1	116	5.3	23.2  ±  8.7
K. 1866	Dnd - M	C	64	12	5	10	91	17.7	21.7  ±  5.0
	Dnd - Chi 32	R	145	63	50	1	258	20.0	14.8  ±  6.0
	M - Chi 32	R	47	22	19	1	89	5.8	22.3 ± 10.0
K. 1973	Dnd - Lum2	R	204	64	71	1	339	20.9	14.6  ±  5.3
	Dnd - M	C	149	28	23	28	228	32.6	26.5  ±  3.5
	Lum2 - M	R	133	55	40	1	229	13.1	16.8  ± 6.4
* The fertile allele unitac was included.

 

 

 

 

 

 

 

 

 

 

1.  Czerwinska, St. and Wolko B.  1991.  Pisum Genetics 23: 14-15.

2.  Swiecicki, W.K.  1984.  PNL, 16: 84-86.

3.  Swiecicki, W.K.  1986.  Genet. Pol. 27: 73-80.

4.  Swiecicki, W.K. and Wolko, B.  1991.  Pisum Genetics 23: 40-41.


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