Rust is one of the most-damaging eucalypt diseases in Brazil and is considered a potential threat to eucalypt plantations worldwide. To determine the mode of inheritance of resistance in the Eucalyptus grandis- Puccinia psidii pathosystem, ten full-sib families, generated from crosses between susceptible and resistant trees, were inoculated with a single-pustule isolate of the pathogen and rust severity was scored. The observed segregation ratios in segregating families suggested major gene control of rust resistance, although clearly incomplete penetrance, variable expressivity and minor genes are also involved in the global rust-resistance response. To identify markers linked to the resistance locus, screening of RAPD polymorphisms was conducted using bulked segregant analysis in a large full-sib family. A linkage group was built around the Ppr1 gene ( P. psidii resistance gene 1) encompassing six RAPD markers, with a genetic window spanning 5 cM with the two most-closely linked flanking markers. Besides these two flanking markers, RAPD marker AT9/917 co-segregated with Ppr1 without a single recombinant in 994 meioses. This tightly linked marker should prove useful for marker-assisted introgression and will provide an initial lead for a positional cloning effort of this resistance allele. This is the first report of a disease resistance gene identified in Eucalyptus, and one of the few examples of the involvement of a major gene in a non-coevolved pathosystem.

Utilizando tamanho de pústulas e número de soros como critérios para avaliar a severidade, estabeleceu-se a seguinte escala de notas para quantificação da ferrugem causada por Puccinia psidii em mudas inoculadas de Eucalyptus sp.: S0 = imunidade ou reação de hipersensibilidade, com necrose ou "fleck"; S1 = pústulas puntiformes, < 0,8 mm de diâmetro; S2 = pústulas medianas, de 0,8 a 1,6 mm de diâmetro; e S3 = pústulas grandes, > 1,6 mm de diâmetro. Aferiu-se essa escala mediante o uso do marcador RAPD AT9/917, geneticamente ligado a um gene de resistência à ferrugem, em uma progênie de E. grandis. Apenas as plantas das classes S0 e S1 apresentaram o referido marcador e foram consideradas resistentes. A inconsistência na classificação de plantas resistentes e suscetíveis foi baixa (8%). O uso dessa escala permitiu a seleção de grande número de plantas resistentes à ferrugem com relativa rapidez, facilidade e precisão.Palavras-chave adicionais: severidade, avaliação da resistência, Puccinia psidii. ABSTRACT Rating scale to eucalypts rust severity evaluationBased on the pustule size, a rating scale was developed for evaluation of rust severity in inoculated seedlings of Eucalyptus sp. as follow: S0 = immunity or hypersensitive reaction, with necrosis or fleck; S1 = small pustules, < 0.8 mm diameter; S2 = medium sized pustules, from 0.8 to 1.6 mm diameter and S3 = large pustules, > 1.6 mm diameter.This scale was checked in a segregant progeny of E. grandis by using the RAPD AT9/917 marker, tightly linked to a rust resistance locus. Only plants classified as S0 and S1 had the RAPD marker and were considered resistant. The error in the classification of resistant and susceptible plants was low (8%). The use of this scale allowed a very fast and accurate screening of rust resistant genotypes.

-Casssava (Manihot esculenta Crantz) is one of the main food and income sources of about 500 million people in the tropics. The crop is mainly cultivated by small farmers in tropical Africa, Asia and Latin America. Embrapa Mandioca e Fruticultura Tropical, based in Cruz das Almas, Bahia, maintains one of the largest cassava genebanks of Latin America. Among the accessions it contains, those with yellow-orange root color are particularly interesting. The objective of this study was to characterize 30 cassava accessions with yellow-orange root color by RAPD markers. The genetic distances of the 47 analyzed primers varied from 9.0 to 31.7 %, demonstrating the existing genetic variability to be exploited for the development of cassava varieties with higher beta-carotene contents.Molecular characterization of Cassava ( Molecular characterization of Cassava ( Molecular characterization of Cassava ( Molecular characterization of Cassava ( Molecular characterization of Cassava (Manihot esculenta Crantz Crantz Crantz Crantz Crantz) ) ) ) ) with yellow-orange roots for beta-carotene with yellow-orange roots for beta-carotene with yellow-orange roots for beta-carotene with yellow-orange roots for beta-carotene with yellow-orange roots for beta-carotene improvement improvement improvement improvement improvement In Brazil, 4132 accessions have been collected and are maintained in genebanks across the country (Fukuda 2000). Carotenes (-carotene, b-carotene, lycopene) represent the most multifaceted group of pigments in nature, with colors varying from yellow to red, found in photosynthetic and non-photosynthetic tissues, such as roots, seeds and fruits. Once ingested, b-carotene is transformed, in the liver, into Vitamin A. Vitamin A is a micro-nutrient with functions related to vision, cell differentiation, growth development, reproduction and the immune system. Vitamin A deficiency (VAD) can cause severe diseases, e.g., ocular syndrome, xerophthalmia, and advance to irreversible blindness (Underwood et al. 1999). Although the lack of vitamin A can be prevented, xerophthalmia is still a public health problem in many developing countries (Welch and Graham 2002). In general, staple foods are considered poor sources of micro-nutrients. Cassava genetic breeding may modify this situation, through the exploration of diversity encountered in yellow-orange root cassava accessions (Gregorio 2002, Welch 2002, Bedoya et al. 2003. Among the accessions of the Cassava Genebank of Embrapa Cassava and Tropical Fruits, those with yellow-orange roots, which have only recently become the subject of thorough studies, deserve special attention. The roots of these accessions possibly contain high b-carotene contents. Moreover, it is known that there is sufficient genetic diversity in the cassava genebanks that can be explored for this trait (Iglesias et al. 1997, Carvalho 2000. The inheritance for b-carotene concentration in cassava roots is controlled by few genes, i.e., the levels of b-carotene in cassava varieties can be improved thr...

Pineapple is one of the most important fruits, with large production in tropical and subtropical regions and great appreciation by consumers all over the world. The pineapple plant has many specific morphological, anatomical and physiological characteristics that determine crucial aspects of pineapple crop management, such as flower induction, water use and vegetative methods of propagation. The use of sexual reproduction of pineapple is restricted to breeding purposes carried out by research institutes looking for new hybrids with improved agronomic characteristics. Seeds are only produced if cross pollination among varieties occurs. Commercially pineapple has to be propagated by vegetative material, an asexual reproduction, without new combinations of genes. Some types of propagules are naturally produced by the plants and called conventional planting material. Its availability and quality depend on many factors, especially cultivar and environment. Management techniques of this material have been continuously developed and will be addressed. In addition to the conventional planting material, which in many situations is not sufficient to assure expansion or at least maintenance of the cultivated area, several other methods of vegetative propagation of pineapple have been studied and made available along the last decades and will also be discussed, involving techniques of stem sectioning, apical growing point gouging and chemical treatment for transformation of flowers into plantlets. Stem sectioning has been especially interesting, as it is mostly done using plant residues available at low cost, and is a rather simple method suited for multiplication and production of disease-free planting material in nurseries. Gouging and chemical treatment are less practiced, but can be applied in ratoon crops, thereby avoiding the loss of the first cycle fruit. Chemical treatment usually results in rather small plantlets, that must be further grown in nurseries before planting them in the field. And finally micropropagation will also be focused, as in vitro production of plantlets is a very important method of multiplication of new pineapple varieties, but this method yet has not been transformed into a common commercial way of pineapple propagation due to the final high cost and to the still high risks of incidence of somaclonal variations among the plantlets produced.