No abstract

Most strawberry (Fragaria × ananassa Duchesne) cultivars used in Brazil are developed in other countries, it became clear the need to start the strawberry breeding program in the country. To start a breeding program is necessary the genetic characterization of the germplasm available. Molecular markers are important tools that can be used for this purpose. The objectives of the present study were to assess the genetic similarity among 11 strawberry cultivars using RAPD and ISSR molecular markers and to indicate the possible promising crosses. The DNA of the eleven strawberry cultivars was extracted and amplified by PCR with RAPD and ISSR primers. The DNA fragments were separated in agarose gel for the RAPD markers and in polyacrylamide gel for the ISSR markers. The genetic similarity matrix was estimated by the Jaccard coefficient. Based on this matrix, the cultivars were grouped using the UPGMA method. The dendogram generated by the RAPD markers distributed the cultivars in three groups while the ISSR markers generated two groups. There was no direct relationship between the marker groups when the two types of markers were compared. The grouping proposed by the ISSR markers was more coherent with the origin and the genealogy of the cultivars than that proposed by the RAPD markers, and it can be considered the most efficient method for the study of genetic divergence in strawberry. The most promising crosses, based on the genetic divergence estimated from the RAPD and ISSR molecular data were between the Tudla and Ventana and the Oso Grande and Ventana cultivars, respectively.

Novel diversity may be mined from databases and de novo sequencing, but functional characterization remains a limiting step to identifying new alleles. Classical breeding approaches augmented by marker‐assisted selection offer a means to rapidly assess the function of new variation in coding or regulatory regions to modulate traits. We used the Cyc‐B gene (B) of tomato (Solanum lycopersicum L.) for a proof of concept because of its role in the production of β‐carotene, a provitamin A carotenoid with importance to human nutrition. We measured carotenoid content in vintage and contemporary varieties and the profiles had a range of β‐carotene from 0.2 to 4.06 mg 100 g−1 fresh weight. We characterized variation in B from 84 sequences recovered from public databases and from an additional 29 high β‐carotene tomato, S. galapagense S. C. Darwin & Peralta, and S. cheesmaniae (L. Riley) Fosberg accessions. Thirteen unique haplotypes across 1600 bp of sequence 5′ to the first ATG were identified with 11 occurring in high β‐carotene accessions we sequenced, and additional haplotypes were identified in public data. Phylogenetic analysis suggested that the alleles in high β‐carotene varieties were derived from wild species. Association analysis suggested two single nucleotide polymorphisms (SNPs) as the most likely causes of high β‐carotene, presumably through their influence on transcription of B that is elevated in ripening fruit. A marker‐assisted backcross breeding scheme leveraging SNPs for background genome selection was used to rapidly develop germplasm resources containing different alleles of B in a uniform genetic background. Evaluation demonstrated that distinct promoter haplotypes function as different alleles that can be used to modulate the levels of β‐carotene in tomato.

Given the growing importance of the saladette fresh tomato market in Brazil, the objective of this paper was to assess the combining abilities of lines potentially useful as parents of hybridsin this class. The experiment consisted of28 genotypes, 18 hybrids from a partial diallel crossobtained from crossing two groups of tomato lines (Group I, with 9 parents, and Group II, with 2 parents), 8 F1 experimental hybrids, and 2 commercial checks. Traits evaluated were total yield, mean fruit mass, fruit shelf life, shape and percentsoluble solids. Additive genetic effects were generally more important than non-additive effects for all traits evaluated. The TOM-542 and TOM-734 lines, from group I, and the TOM-720 line, from group II, presented high general combining ability (GCA) estimates for most of the traits of importance for saladette tomatoes, and were therefore considered suitable parents of hybrids of this class. Higher fruit shelf life of TOM-723 as a parental line compared with TOM-720 (Group II), was mainly attributed to the presence in the former of the nor A allele, which controls longer fruit shelf life. F1 hybrids (TOM-542 x TOM-720), (TOM-580 x TOM-720), (TOM-734 x TOM-720), and (TOM-727 x TOM-720) showed good performance and fruit quality and thus constitute possible commercial varieties.Key words: Solanum lycopersicum, saladette tomatoes, partial diallel. Capacidade combinatória de linhagens de tomateiro em híbridos do tipo italiano ResumoDevido à crescente importância do mercado do tomate tipo italiano no Brasil, objetivou-se conhecer a capacidade combinatória de linhagens de tomateiro potencialmente utilizáveis como genitoras de híbridos voltados a esse segmento. O experimento constituiu-se de 28 genótipos, sendo 18 híbridos oriundos de um dialelo parcial, obtido pelo cruzamento entre dois grupos de linhagens: Grupo I (nove genitores) e Grupo II (dois genitores), oito híbridos adicionais e duas testemunhas comerciais. Foram avaliados produção total, massa média de frutos, firmeza, formato e teor de sólidos solúveis. Houve predominância dos efeitos gênicos aditivos para todas as características avaliadas. As linhagens TOM-542 e TOM-734, pertencentes ao Grupo I, e TOM-720, Grupo II, apresentaram estimativas elevadas de capacidade geral de combinação para a maioria das características de importância para o segmento de tomate italiano, portanto, recomendadas para a obtenção de híbridos desse tipo. A superioridade da linhagem TOM-723 sobre a TOM-720 (Grupo II) quanto à firmeza de frutos foi atribuída, principalmente, à presença, na primeira, do alelo nor A , que condiciona maior conservação pós-colheita. Os híbridos experimentais F1 (TOM-542 x TOM-720), F1 (TOM-580 x TOM-720), F1 (TOM-734 x TOM-720) e F1 (TOM-727 x TOM-720) apresentaram bom desempenho agronômico e qualidade de fruto, constituindo possíveis materiais comerciais.Palavras-chave: Solanum lycopersicum, tomate saladette, dialelo parcial.

Current climate change models predict an increased frequency and intensity of drought for much of the developing world within the next 30 years. These events will negatively affect maize yields, potentially leading to economic and social instability in many smallholder farming communities. Knowledge about the genetic resources available for traits related to drought tolerance has great importance in developing breeding program strategies. The aim of this research was to study a maize landrace introgression panel to identify chromosomal regions associated with a drought tolerance index. For that, we performed Genome-Wide Association Study (GWAS) on 1326 landrace progenies developed by the CIMMYT Genetic Resources Program, originating from 20 landraces populations collected in arid regions. Phenotypic data were obtained from early testcross trials conducted in three sites and two contrasting irrigation environments, full irrigation (well-watered) and reduced irrigation (drought). The populations were genotyped using the DArTSeq® platform, and a final set of 5,695 SNPs markers was used. The genotypic values were estimated using spatial adjustment in a two-stage analysis. First, we performed the individual analysis for each site/irrigation treatment combination. The best linear unbiased estimates (BLUEs) were used to calculate the Harmonic Mean of Relative Performance (HMRP) as a drought tolerance index for each testcross. The second stage was a joint analysis, which was performed using the HMRP to obtain the best linear unbiased predictions (BLUPs) of the index for each genotype. Then, GWAS was performed to determine the marker-index associations and the marker-Grain Yield (GY) associations for the two irrigation treatments. We detected two significant markers associated with the drought-tolerance index, four associated with GY in drought condition, and other four associated with GY in irrigated conditions each. Although each of these markers explained less than 0.1% of the phenotypic variation for the index and GY, we found two genes likely related to the plant response to drought stress. For these markers, alleles from landraces provide a slightly higher yield under drought conditions. Our results indicate that the positive diversity delivered by landraces are still present on the backcrosses and this is a potential breeding strategy for improving maize for drought tolerance and for trait introgression bringing new superior allelic diversity from landraces to breeding populations.

Resumo: O objetivo deste trabalho foi verificar a resistência à lagarta Helicoverpa armigera (Lepidoptera: Noctuidae), em genótipos de tomateiro obtidos do cruzamento interespecífico de Solanum lycopersicum x S. galapagense, e a associação dessa resistência com a densidade de tricomas glandulares do tipo IV. Genótipos da população F2, derivada do cruzamento S. lycopersicum TOM-684 x S. galapagense LA-1401, selecionados quanto à baixa e à alta densidade de tricomas glandulares, respectivamente, foram submetidos a dois testes de resistência à lagarta H. armigera em laboratório, um de antibiose e outro de antixenose. Os genótipos da população F2, com alta densidade de tricomas glandulares do tipo IV (BPX-486-17, BPX-486-62, BPX-486-10, BPX-486-46 e BPX-486-08), apresentam maiores níveis de resistência, tanto por antibiose quanto por antixenose, do que os genótipos com baixa densidade de tricomas glandulares (BPX-486-313 e BPX-486-383) e do que as testemunhas 'Santa Clara' e TOM-684. Os níveis de resistência foram menores do que os do genitor silvestre LA-1401.

Resumo -O objetivo deste trabalho foi avaliar a capacidade combinatória de linhagens de tomateiro com hábito de crescimento determinado, com resistência múltipla a espécies dos gêneros Begomovirus e Tospovirus, e identificar combinações híbridas superiores. O experimento foi realizado em casa de vegetação, com 14 híbridos obtidos do cruzamento de sete linhagens femininas (grupo I) com duas linhagens masculinas (grupo II), em um dialelo parcial. As seguintes características agronômicas foram avaliadas: produção total, produção precoce, massa média de frutos, formato, firmeza inicial e firmeza na meia-vida. As linhagens genitoras TOM-680 e TOM-682, do grupo I, se destacaram por exibir as maiores estimativas de capacidade geral de combinação (CGC) quanto às características produção total, produção precoce e massa média de frutos, enquanto a linhagem TOM-585 se destacou quanto aos maiores valores de produção total e massa média de frutos. No grupo II, a linhagem TOM-698 apresentou estimativas superiores de CGC para as características de produção total, produção precoce, massa média dos frutos e firmeza inicial dos frutos. O híbrido TOM-682xTOM-698 apresenta as maiores estimativas de capacidade geral e específica de combinação para produção total, produção precoce e meia-vida da firmeza, e é o genótipo mais promissor entre os materiais testados.Termos para indexação: Solanum lycopersicon, análise dialélica, geminivírus, melhoramento, resistência. Combining ability of determinate-growth-habit tomato hybrids resistant to Begomovirus and TospovirusAbstract -The objective of this work was to evaluate the combining ability of determinate-growth-habit tomato inbred lines with multiple resistance to Tospovirus and Begomovirus species, ant to identify superior hybrid combinations. The experiment was carried out in greenhouse, with 14 hybrids obtained from crosses of seven lines of the group I (female parents) with two lines of the group II (male parent), in a partial diallel.The following agronomical traits were assessed: total production, early production, mean fruit mass, shape, initial firmness and half life firmness. The parental lines TOM-680 and TOM-682, from group I, stand out with the largest general combining ability (GCA) concerning total production, early production and average fruit mass, while line TOM-585 stood out as to higher values of total production and average fruit mass. In group II, TOM-698 showed higher estimates of GCA as to total production, early production, average fruit mass and initial consistence of the fruits. The hybrid TOM-682xTOM-698 had the highest estimate of general and specific combining ability to total production, early production and average fruit mass, and it is the most promising genotype among the materials tested.

The aim of this study was to verify the resistance of tomato genotypes (crossed with Solanum galapagense) to the green peach aphid, Myzus persicae, and the association of this resistance with glandular trichomes. Leaf trichomes were quantified for seven F2 genotypes of the BPX-486 population derived from crossing S. lycopersicum ‘TOM-684’ and S. galapagense accession ‘LA-1401’, for the commercial controls ‘TOM-584’ and ‘Santa Clara’, and for the accession ‘LA-1401’. After this evaluation, the genotypes were subjected to two nonpreference resistance tests of the green peach aphid in the laboratory, one with choice and the other without choice. Five genotypes (BPX-486-17, BPX-486-62, BPX-486-10, BPX-486-46, and BPX-486-08) and the accession LA-1401 exhibited a high density of type IV glandular trichomes and a lower mean number of nymphs and adults of M. persicae than two genotypes (BPX-486-313 and BPX-486-383) and the controls with a low density of glandular trichomes, in all the evaluations of both tests. Significant negative correlations between the density of type IV glandular trichomes of the tomato genotypes and the preference of M. persicae were found, which confirms the association between this type of glandular trichome and resistance to M. persicae in tomato genotypes.