A new gene for precocious yellowing on linkage group I
Swiecicki, W.K. and Irzykowska, L.
Institute of Plant Genetics
Polish Academy of Sciences
Strzeszynska 34, 60-479 Poznan, Poland
The spontaneous mutant gene precocious yellowing (py) isolated and described by Marx [1], is located on linkage group V (the type line = Marx’s C 75-27, catalog number in the Polish gene bank Wt 12134). The phenotype of the mutant is the early yellowing (before flowering) of the initial normally green foliage. Stem and pods also become yellow rapidly (py pods in contradistinction to gp have green upper suture).
A mutant of the cv. Porta (Wt3519) with identical phenotype was selected in Wiatrowo in 1982 in the M2 generation following treatment of dry seeds with 7 krad of X-radiation. To test for allelism, crosses were made between the new mutant (designated Wt 12130) and the type line for py (Wt 12134). The F1 plants displayed a normal phenotype, indicating that the two mutants are not allelic. We propose a common name precocious yellowing for both mutations and suggest the following symbols for the genes: py1 for the Marx’s gene and py2 for the new gene. The line Wt 12129 was selected from the F2 generation of the cross Wt 12130 x Wt 11238 and used for further genetical analysis because py2 exhibited better expression in this line.
To determine the map location of the new mutant the line Wt 12129 (py2) was crossed with marker lines for seven linkage groups. Evidence for linkage was obtained with markers on LG I in cross K. 1643 (Wt 12129 ? afila - breeding line) and K. 1641 (Wt 12129 x Wt 10584 [aero]). Segregation ratios obtained for py2 confirmed its monogenic nature (Table 1). Joint segregation analysis gave a recombination percentage of 10.7 between py2 and af and a similar percentage (9.5) between py2 and aero (Table 2).
Table 1. Monohybrid segregation at loci on linkage group I in the F2 populations of crosses K. 1643 and K. 1641| Cross | Locus |
Phenotype |
Total |
c 2 |
||
D |
R |
(3:1) |
||||
K. 1643 |
Py2 |
319 |
91 |
410 |
1.72 |
|
Af |
310 |
101 |
411 |
0.04 |
||
K. 1641 |
Py2 |
427 |
113 |
540 |
4.78 |
|
Aero |
407 |
143 |
550 |
0.29 |
||
* P < 0.05
Table 2. Joint segregation analysis of Py2 and loci on linkage group I in F2 populations of crosses K. 1643 and K. 1641
| Cross | Loci |
Phenotype. |
Joint c2 | % recomb + std. error |
||||
DD |
DR |
RD |
RR |
Total |
||||
K. 1643 |
Py2, Af |
218 |
101 |
91 |
1 |
410 |
37.2 |
10.7 + 4.9 |
K. 1641 |
Py2, Aero |
287 |
138 |
113 |
1 |
538 |
49.3 |
9.5 + 4.3 |
The locus O, also producing a yellowing of the foliage, is located near Af. As the phenotype of the o mutant is somewhat similar to that of precocious yellowing, it was necessary to test for allelism between py2 and o. The F1 plants from crosses between lines homozygous for py2 and lines homozygous for o displayed a normal green foliage, demonstrating that py2 is not allelic to o.
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1. Marx, G.A. 1971. Pisum Newsl. 3: 20-21.