Pisum Genetics
2008—Volume 40
Research Papers
Floral mutants: Allele designations at the Lst and the A loci
and the mapping of Sypl
Xin L.1 Rameau, C. 2 Luo, D. 1,3 Amborse, M4
1Shanghai Jiao Tong University, Shanghai, China 2 Institut J.P. Bourgin, INRA, Versailles, France 3Shanghai Institutes for Biological Sciences, Shanghai, China
4John Innes Centre, Norwich, UA
Pea flowers, like most zygomorphic flowers, possess a prominent corolla with three petal types, which are arranged along a dorsoventral (DV) axis. In order to study the genetic mechanism of floral zygomorphy in pea, screening for floral mutation was carried out on material generated in two mutagenesis programs at the John Innes Centre, INRA Versailles Centre and SIPPE. Several floral mutants affecting the development of DV asymmetry were recovered and two mutants displaying deficiency in the development of organ internal (IN) asymmetry were isolated.
A mutation at the LOBEDSTANDARD1(Lstl) (1) locus gives rise to the abnormal shape in the dorsal petals. lstl-1 (registered as JI 3021) was a spontaneous event in JI 321 found in 1985 (1). lstl-2 (FN 3046/67) and lstl-3 (FN 3194/1343) were isolated in a fast neutron mutagenesis population of JI 2822 in 2006 and found to be allelic in crosses to JI 3021. The mutation at the KEELED WINGS (K) locus (2) is a classic marker line for genetic analysis. Two further lines were identified in the germplasm collection as having the same phenotype were found to be allelic in crosses to JI 73 which carries the same mutation as JI 17. k-2 (JI 3260) arose by x-ray mutagenesis, and k-3 (JI 3261) was derived from fast neutron mutagenesis in JI 116 and JI 2296, respectively.
Table 1. Monohybrid segregation for the gene symmetrical petals (sypl) in a single F2 population.
|
Cross
|
Gene
|
Dom
|
Rec
|
Total
|
Chi square
|
||
|
PDL099 x JI 992
|
syp1
|
524
|
170
|
694
|
0.094
|
||
During mutant screens, mutants bearing petals with altered IN asymmetry were identified and found to be allelic. The gene symbol Sypl (symmetrical petals) was proposed. Mutants sypl-l (PDL099) and sypl-2 (FN 3443/2317) (3) were derived from EMS and fast neutron mutagenesis in Terese and JI 2822 respectively. In sypl-l, nearly all petals are bilaterally symmetrical but maintain their DV identities. sypl-2, a weaker allele, has a highly variable effect on IN asymmetry of the lateral but not the ventral petals. In an effort to map the sypl locus, sypl-l was crossed with JI 992. A single F2 population of 694 plants were sown in greenhouse of which 170 were of mutant phenotype with symmetrical petals (Table 1) which demonstrated that sypl behaves as a single recessive gene. Using the mapping population, the sypl locus has been located between gene-based marker GbSTS1 and LegJ in linkage group II of pea (Fig.1) (4) and the gene-based dCAPS marker Puttip which co-segregated with syp1 with no recombinants detected. Allele designations of all the lines described are represented in Table 2. All germplasm lines referred to in this article are available from the John Innes Pisum Collection and are detailed in the Pisum gene list (5).
19