Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Relação do zinco e cobre plasmáticos com componentes nutricionais e desempenho de leitões: uma meta-análise Relation of plasma zinc and copper with nutritional components and performance of weanling pigs: a meta-analysis

Foi realizada uma meta-análise para estudar a relação do zinco (Zn) e cobre (Cu) plasmáticos com os nutrientes da dieta e ganho de peso em leitões. A base de dados contemplou 18 publicações. As variáveis nutricionais consideradas na análise foram ingestões de PB, lisina, Ca, P, Cu e Zn. Foram realizadas análises de regressão por intermédio de modelos mistos. O Zn plasmático foi influenciado pelo P, Zn ingeridos e Cu plasmático. O P ingerido e Cu plasmático afetaram negativamente o Zn plasmático. A análise de regressão mostrou que, para cada grama de P total ingerido/kg PV0,6, houve redução de 0,043 mg/L de Zn plasmático. O Cu plasmático foi influenciado pelo Ca, P, Cu e o Zn ingerido. O Ca e Zn ingerido afetaram negativamente o Cu plasmático. O ganho de peso foi influenciado pela PB, Ca, lisina e Cu ingeridos e o Zn plasmático. O Zn ingerido apresentou efeito negativo no metabolismo do Cu, mas o Zn plasmático teve influência positiva no ganho de peso. Neste estudo de meta-análise, identificaram-se alguns fatores de origem dietética, como o P e Ca, que influenciam negativamente a absorção e o metabolismo de Zn e Cu em leitões.<br>A meta-analysis was carried out to study the relationship among plasma Zn and Cu with diet nutrients and piglets weight gain. Eighteen publications were considered in the database. The intake of CP, lysine, Ca, P, Cu and Zn was considered as variable in the analysis. Regression analyses were used through mixed models. Plasma Zn was affected by P and Zn intake as well as Cu plasma. P intake and plasma Cu affected negatively plasmatic Zn. The regression analysis showed that for each gram of total P intake/kg BW0.6 there was reduction in 0.043 mg/L of plasmatic Zn. Plasma Cu was affected by Ca, P, Cu and Zn intake. Ca and Zn intake affected negatively plasma Cu. Weight gain was affected by CP, Ca, lysine and Cu intake as well as plasma Zn. A negative effect of Zn intake on Cu metabolism was observed; however plasma Zn had a positive effect on piglets weight gain. This meta-analysis study identified some factors of dietary origin, as P and Ca, which influence negatively the absorption and the metabolism of Zn and Cu in weanling pigs