Chromosome reconstructions in P. sativum through interspecific hybridization with P. fulvum.

Pisum spp. exhibit polymorphism for the number of secondary constrictions: P. sativum contains two pairs of satellited chromosomes (4 and 7), while P. fulvum has three pairs (4, 5 and 7). The satellite of chromosome 7 is longer in P. fulvum than in P. sativum. Reconstructions were obtained in chromosomes 5 and 7 through interspecific hybridization between P. sativum and P. fulvum, followed by five backcrosses with P. sativum as recurrent parent. Modified chromosomes 5 and 7 showed an additional secondary constriction and a longer satellite, respectively. A deficiency of backcross plants carrying the additional NOR on chromosome 5 was observed, the segregation showing a significant deviation from the expected 1 : 1 ratio. This deficit was not related to the chromosome interchanges observed in the material. Near all the plants with modified chromosome 5 presented modified chromosome 7, suggesting that the simultaneous presence of both the modofied chromosomes recovers a genic equilibrium, allowing the development of plants with chromosome reconstructions. The chromosome reconstructions were not associated with any noticeable morphological characteristic