New alleles at the am1 and red loci on linkage group IA

Rozov, S.M., Gorel, F.L. †††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††Institute of Cytology and Genetics
and Berdnikov, V.A. ††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††††Novosibirsk 630090, Russia

Mutants SGE-0659 and SGE-0292 were isolated from the M2 generation after treatment of the line SG with 0.15% EMS. The SGE-0659 mutant has white flowers, normal anthocyanin-coloured violet stipule ring (maculum), and violet dots on the seed testa caused by the gene Fs. Mutant line SGE-0292 has flowers with a pale-pink standard (vexillum) and pink wings; the flower coloration is very similar to the coloration caused by the gene b. The stipule anthocyanin ring and coloured dots on the seed testa of this line are pale-pink while the testa background, which is normally green in the initial line SG, is ochrous, with more intensive coloration around the hilum and halaza-spot. Another mutant line, SGR-am, obtained independently from line SG by treatment with 7 krad of gamma-rays, has practically the same pattern of coloration as line SGE-0292.

These three mutant lines were crossed with line WL-1132, which carries a recessive allele of the gene am1 (2). The am1 mutation causes the absence of anthocyanin in flower structures but does not affect the coloration of the other parts of the plant. The three new mutants all appeared to be allelic with Lamprechtís am1 gene.

Table 1 shows the main differences in the effects of the different alleles of am1 on the pattern of coloration. It is clear from the phenotypes of the new mutants that the am1 gene is expressed not only in the flower structures, as suggested earlier (1), but may also be expressed in several anthocyanin-coloured pea organs. Moreover, the ochrous coloration of the seed testa in lines SGE-0292 and SGE-am is more probably the result of producing pigments of a flavonoid nature rather than anthocyanins.

We propose to symbolize the three new mutant alleles am1-2 (type line SGE-0659), am1-3 (SGE-0292) and am1-4 (SGE-am). The dominance relationships between each of these alleles and the original mutant allele am1-1 (type line WL-0369) vary with the trait under consideration, as illustrated by the results in Table 1.

Table 1. Effect of different mutant alleles at the am1 locus on coloration of several pea structures.

Line or F1 hybrid Allelle(s) Flower Stipule

ring

Testa (background)

Testa

(Fs spots)

WL-1132 am1-1 white, sometimes veins pale pink normal

normal

normal
SGE-0659 am1-2 white pale pink

normal

normal
SGE-0292 am1-3 pink pale pink

ochrous

pale pink

SGR-am am1-4 pink pale pink

ochrous

pale pink

WL-1132 SGE-0292 am1-1/am1-3 pink pale pink

normal*

normal
WL-1132 SGR-am am1-1/am1-4 pink pale pink

normal*

normal
WL-1132 SGE-0659 am1-1/am1-2 white pale pink

normal

normal

*Sometimes a pale ochrous ring around the hilum.

††

Fig. 1. Leaves of the red1-2 mutant line SGE-0634 (left) and initial line SG (right).

††

Mutant SGE-0634 was isolated from the M2 population after treatment of line SG with EMS. This mutant is characterised by a 50% reduction in the width of stipules and leaflets, a narrow leaflet base and curled stipules (Fig. 1). A cross with WL-1748, which carries a recessive allele of the gene red (reduced) (1), showed that the new mutant is allelic to red and the new allele dominant to the original mutant allele: all F1 plants were of the SGE-0634 phenotype. We propose to symbolise the new allele red1-2 with SGE-0634 as the type line. Plants carrying the red1-2 allele are 4 to 5 times more fertile than red1-1 plants and produce only a slightly decreased amount of seeds as compared with the initial line, SG. Therefore, the new allele red1-2 is more convenient for genetic experiments than Lamprechtís red1-1 allele, which severely decreases the overall green mass of the plants and causes them to be almost sterile.

Two linkage crosses were made using mutant lines SGE-0659 and SGE-0634. The F2 data (Table 2) confirm the tight linkage of genes am1 and red with gene i established by Lamprecht (1, 2). The small size of F2 population does not permit an unambiguous order of the three genes to be established.

Table 2. F2 data showing linkage between genes am1, i and red.

Gene

Phase

Number of progeny with phenotype1

Joint

RCV

SE

pair

A/B

A/h

A/b

a/B

a/h

a/b

Chi-sq
Cross SGE-0659 (am1-2) WL1514
am1 i

C

48

-

1

0

-

27

71.8***

1.5

1.2

Cross SGE-0634 (red1-2) WL1132 (am1-1)
red i

C

24

39

1

0

0

11

67.7***

1.6

1.5

am1 i

C

12

36

5

0

3

19

42.5***

9.7

3.6

red am1

R

52

-

23

11

-

0

4.6

< 29

10

1 A/a, first gene; B/b, second gene; h, heterozygous at the i locus as determined by examining F3 seeds. ***P < 0.0001.

Acknowledgement. This work was partially supported by the Russian State Program for Fundamental Research.

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1. Lamprecht, H. 1948. Agri Hort. Genet. 6:10-48

2. Lamprecht, H. 1957. Agri Hort. Genet. 15:155-168.

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