Pisum Genetics Volume 27 1995 Research Reports page 22

Linkage of gene chi-33 on linkage group VI

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

and Kruszka, K. Strzeszynska 34, Poznan 60-479, Poland

The spontaneous chlorotica mutation chi-33 (Wt11019) shows clear expression at the seedling stage except under greenhouse conditions (1). A preliminary linkage test (1) indicated significant linkage between chi-33 and linkage group VI marker Pl (29 cM) but linkage with wlo on this chromosome was not significant.

To locate chi-33 more precisely, we crossed Wt11019 with tester line Wt11777 which carries four group VI markers Pl, Arg, wlo and art-1. In the F₂, chi-33 and the four markers all showed normal monohybrid segregation (Table 1). Dihybrid segregation analyses (Table 1) provided strong evidence of linkage between chi-33 and markers Arg (P<0.0001, 13.6 cM) and Pl (P<0.0001, 16.7 cM) but only weak evidence of linkage between chi-33 and markers wlo (P<0.01, cM 25.4) and art-1 (P<0.05, 29.7 cM). Together with the previous data (1), these results indicate chi-33 is located in the linkage group VI and closer to Pl than wlo. The data in Table 1 suggest the following arrangement of loci:

Table 1. Monohybrid (a) and dihybrid (b) segregation in the F₂ population of the cross
K. 1317 = Wt 11019 (chi-33, arg, pl, Art-1, Wlo) x Wt 11777 (Chi-33, Arg, Pl, art-1, wlo).

(a)	Phenotype*							Chi-sq. (3:1)
Locus	D		R			Total
Chi-33	100		30			130		0.26
Arg	98		32			130		0.01
Pl	96		31			127		0.02
Art-1	102		27			129		1.14
Wlo	96		34			130		0.09
(b)	Phenotype*							Joint Chi-sq.	Recomb fract.	SE
Loci	DD	DR		RD	RR		Total
Chi-33/Arg	91	9		7	23		130	56.9	13.6	3.2
Chi-33/Pl	88	11		8	20		127	43.0	16.7	3.7
Arg/Pl	95	2		1	29		127	111.1	2.3	1.3
Chi-33/Art-1	75	25		27	2		129	4.4	29.7	7.9
Chi-33/Wlo	68	32		28	2		130	7.7	25.4	8.1

*D = homozygous dominant + heterozygous; R = homozygous recessive

1. Apisitwanich, S. and Swiecicki, W.K. 1993. Pisum Genetics 25:17.