The sequence 18/25S rDNA from soybean

and the TTTAGGG from A. thaliana were used as probes

to analyze the genomic organization of Pisum sativum, P.

fulvum and a F4 line (P. sativum X P. fulvum) by fluorescent

in situ hybridization (FISH). The experiment was conducted

at the University of Córdoba, Spai n during the summer of

2006. The probe 18/25S produced varia ble signals in the

three genotypes. These rDNA signals correspond to the

nucleolar organizing pai rs (NOR `s) on chromosomes 4 and

7 of P. sativum, and 4, 7 and 5 of P. fulvum. The intensity

of signals varie d from very strong to moderately-strong in P.

sativum to small and secrete in P. fulvum, suggesting clear

differences on the number of times that the sequence 18/25S

is repea ted in the genome of these two specie s. Si gnals

observed in the F4 line using the rDNA probe resembled P.

sativum and P. fulvum knobs. Two NOR `s were observed on

the F4 line, although one of the lines showed very low signals

for one pai r of chromosomes. The TTTAGGG sequence

hybridized with the telomeres of the three lines, which shows

that the telomeric sequence from A. thaliana is also present

in the Pisum genera.

Keywords: Cyto-genetics, fluorescent in situ hybridization, NOR, 18/25S rDNA, TTTAGGG.