RESUMO
To evaluate the mitotic stability of Triticum aestivum x Thinopyrum ponticum derivatives (BC(2)F(7) and BC(2)F(5) doubled haploids), chromosome counting by both conventional and immunostaining techniques, and measurement of DNA content were performed. The wheat progenitor line, PF 839197, the wheat recurrent parent CEP 19 and the control Chinese Spring were also investigated. In the hybrid derivatives, chromosome number ranged from 2n=36 to 60, with a predominance of chromosome numbers higher than 2n=42, that was confirmed by determination of nuclear DNA content. Chinese Spring' and PF 839197 were stable, but CEP 19 showed chromosome number variation (20%). Analyses of non-pretreated cells revealed the presence of anaphase bridges, lagging chromatids, chromosome fragments and micronuclei. Immunostaining with an antibody recognizing histone H3 phosphorylated showed dicentric chromatids forming anaphase bridges and pericentromeric phosphorylation at centric chromosome fragments but not at lagging chromatids. The possible causes of the observed mitotic instability are discussed.
Assuntos
Instabilidade Cromossômica , Cromossomos de Plantas/genética , DNA de Plantas/genética , Histonas/genética , Mitose/genética , Triticum/genética , Núcleo Celular/genética , Quimera , Cruzamentos Genéticos , Histonas/metabolismo , Cariotipagem , Fosforilação , Plantas Geneticamente ModificadasRESUMO
Adult plant resistance to leaf rust in the Brazilian wheat cultivar Toropi (Triticum aestivum) was studied in crosses with the susceptible cultivar IAC 13. Cvs. Toropi and IAC 13 are susceptible at the seedling stage to race LCG-RS of Puccinia triticina Erikss., and to all other known Brazilian leaf-rust races. Thus, the resistance observed in Toropi in the field was due to adult plant-resistance genes. In the greenhouse at the adult plant stage, resistance segregated in a 7:9 ratio for two complementary recessive genes. Additionally, two recessive genes for leaf-tip necrosis were identified in the greenhouse environment. Necrosis was expressed when the two homozygous recessive genes occurred together in the F2, independently of the response to leaf rust. The resistance and leaf-necrosis genes differ from those previously reported in wheat. Segregation for leaf-rust resistance in the field at Passo Fundo, Brazil, fit a 1:3 ratio for a single recessive gene. With a different pathogen race, and in crosses of cvs. Toropi and ThatcherLr34, two recessive genes and a dominant gene for resistance were detected in the field in Mexico. The dominant gene was likely Lr34 from cv. ThatcherLr34 and the two recessive genes were likely those detected in the greenhouse adult plants tests at Passo Fundo.
