Analysis of a valuable chromosome rearrangement induced by ionizing radiations in cultivated chili pepper line (Capsicum baccatum var. pendulum - Solanaceae).

SCALDAFERRO, M.; GRABIELE, M.; SEIJO, G.; DEBAT, H.; DUCASSE, D.; PRINA, A.; MOSCONE, E.

Viena

Simposio; FAO/IAEA International Symposium on Induced Mutations in Plants (ISIMP).; 2008

FAO/IAEA

Capsicum (chili peppers) is an important genus including five crop species consumed by man as spice and food. Most contributions about induced mutagenesis in Capsicum refer to gene mutations while induced changes at chromosome level are scarce. We started a program to achieve chromosome rearrangements by ionizing radiations in C. baccatum variety pendulum cultivar "cayenne", which has a karyotype with 2n=2x=24, 11 metacentrics + 1 subtelocentric pairs, 4 pairs (# 1, #3, # 10, # 12) carrying nucleolar organizing regions (NORs) and associated satellites in short arm. Seeds were treated with different acute doses of X-rays developing M1_4generations. A rearranged chromosome carrying NORs in both arms was found in M2 seedlings from the only surviving MI plant after a 300 Gy treatment. The structural change was analyzed by: 1) Feulgen's staining to observe chromosome number, size and shape; 2) silver impregnation to detect active NORs; 3) fluorescent chromosome banding to reveal type and position of constitutive heterochromatic regions [triple staining with chromomycin/distamycin/4-6-diamidino-2-phenylin (CMA/DA/DAPI)]4;) fluorescent in situ hybridization with 18S- 25S rDNA repeated sequence as probe. A reciprocal translocation between two NOR-bearing chromosomes in the MI plant has occurred, which gave viable progeny carrying the chromosomal interchange without any deviating phenotype after four generations, nor in heterozygous neither in homozygous condition. The lack of chromosome instability suggests a small reciprocal interchange between a member of pair # 1 and of #3, both carrying active NORs in shorts arms. The results of this rearrangement were two chromosomes with little change in size, one of them easily recognized by the presence of NORs and associated CMA+/DAPI- heterochromatin in both arms. As the translocation here reported produced a conspicuous rearranged marker chromosome, the obtained plant line is considered very valuable for studies on chromosome pairing and genetic linkage in the genus, including mapping of crop quality genes. This work was supported by the Intemational Atomic EnergyAgency,RBF 12226.