Abstract The sweet potato is an alternative energy source, but its sustainability depends on efficient water use. The objective of this study was to evaluate sweet potato morpho-physiological characteristics, and water use efficiency (WUE). Irrigation depths of 50, 75, 100, and 125% of crop evapotranspiration (ETc) were applied. The morpho-physiological indicators, WUE, leaf area index (LAI), leaf water potential, leaf temperature, and leaf chlorophyll index (ICF), were evaluated. The WUE of the sweet potato cultivars increased until the 75% water depth of the ETc. The LAI of these cultivars increased with irrigation depth, with higher values at 100% of the ETc. The leaf water potential of the two sweet potato cultivars was lowest with the lower irrigation depth. Leaf temperature was closer to that of ambient temperatures in treatments with greater irrigation depth. The increase of the WUE with the greater accumulation of dry biomass is due to greater CO2 diffusion by stomata. The reduction in the growth of these plants is due to water stress limiting stomatal conductance, transpiration, leaf growth (LAI) and chlorophyll concentration, proportional to soil moisture conditions. The functional relationship between soil moisture and growth is essential to optimize irrigation management at different growth stages.

Begomoviruses are whitefly-transmitted single-stranded DNA viruses of great economic importance in the tropics and subtropics. Several begomovirus species have been reported in tomatoes in Brazil, but only a few predominate in the field, for unknown reasons. In this study begomovirus-infected tomato samples were collected in Viçosa, State of Minas Gerais, in Nov/2009 and Dec/2010. Viral genomes were amplified, cloned and sequenced. A total of 36 DNA-A components were obtained. Sequence comparisons indicated the presence of a single begomovirus, Tomato severe rugose virus (ToSRV), with pairwise identities between isolates ranging from 97.3 to 100%. Subdivision tests indicated the existence of a single population. The analysis of variability descriptors indicated that the ToSRV population has a genetic variability similar to other begomovirus populations described in Brazil infecting tomato. Neutrality tests suggested the occurrence of purifying selection acting upon the population. Recombination analysis identified recombination events with begomoviruses from the weed species Sida micrantha. The wide distribution of ToSRV in the field and the detection of recombination indicate that continuous monitoring of viral populations in the field will be required to enable an efficient resistance-based control strategy for begomoviruses.

O objetivo desse trabalho foi estudar a densidade de tricomas e os hidrocarbonetos associados à resistência por antixenose de 42 subamostras de tomateiro do Banco de Germoplasma de Hortaliças da Universidade Federal de Viçosa (BGH-UFV) a Liriomyza trifolii. Essas subamostras foram estudadas e a cultivar 'Santa Clara' que foi utilizada como padrão de suscetibilidade a insetos minadores. As características avaliadas foram os números de folíolos minados/planta, minas/planta, densidade de tricomas e compostos químicos presentes nas folhas. Detectaram-se diferenças entre as subamostras nas variáveis avaliadas. Foram identificados 20 picos nos cromatogramas dos extratos hexânicos das folhas das subamostras testadas. As subamostras HGBs - 216, 813, 985, 987, 991, 992, 993, 1532, 1989, 1991, 2048, 2055, 2064, 2068, 2073, 2075, 2089, 2096 e 2097 foram selecionadas como fontes de resistência a L. trifolii. O mecanismo de resistência associado dessas subamostras foi a antixenose. Além disso, a baixa densidade de tricomas e compostos químicos presentes nas subamostras avaliadas podem ser as possíveis causas da resistência à praga.

The objective of this work was to study the density of trichomes and hydrocarbons associated with the resistance by antixenosis of 42 subsamples of tomato plants from the Horticultural Germplasm Bank of the Universidade Federal de Viçosa (HGB-UFV) to Liriomyza trifolii. These subsamples were studied in addition to 'Santa Clara' cultivar, which was used as a standard of susceptibility to leafminers. The evaluated characteristics were the number of mined leaflets per plant, mines per plant, trichome density and chemical compounds in the leaves. Differences were detected among the subsamples in the variables studied. We identified 20 peaks in the chromatograms of leaf hexane extract the subsamples tested. The subsamples HGBs - 216, 813, 985, 987, 991, 992, 993, 1532, 1989, 1991, 2048, 2055, 2064, 2068, 2073, 2075, 2089, 2096 and 2097 were selected as sources of resistance to L. trifolii. The resistance mechanism associated to these subsamples was antixenosis. In addition, the low density of trichomes and the chemical compounds in the subsamples can be possible causes of pest resistance.

The aim of this study was to evaluate methods for developing a Brazilian maize core collection. For an initial survey of the active collection, passport information, as well as characterization and evaluation of accessions, were taken into consideration, these then being divided according to geographic region and kernel-type. Multiple sampling methods were evaluated. The strategy of constant sampling generated extensive alterations in extract accession frequency. The multivariate strategy with dispersion graphs and principal components associated with the Tocher method was considered efficient for identifying the most divergent genotypes. The multivariate strategy generated greater alterations in the variance of traits. The average number of traits revealed few modifications with the various sampling strategies used. Therefore, the active collection could be considered as possessing a satisfactory amount of information for most of its accessions. Moreover, the multivariate strategy generated modifications in the variance of the traits, independent of sampling intensity.

Com o objetivo de estudar as capacidades específica e geral de combinação (CEC e CGC, respectivamente) entre dois grupos de Lycopersicon spp., obtiveram-se híbridos interespecíficos de tomateiro utilizando-se o modelo de cruzamento dialélico parcial. Foram avaliadas sete características de resistência destes grupos ao ataque de Tuta absoluta. Foram observadas diferenças significativas quanto a maioria das características com relação às capacidades geral e específica de combinação. Baseado na CGC, os genótipos Ângela, Santa Clara, LA 716, e LA 1777 são os parentais mais indicados a serem incluídos em programas de melhoramento do tomateiro que visem aumentar a resistência a T. absoluta. As combinações híbridas com maiores valores conjuntos de CEC e heterose foram Ângela x PI 126445, Ângela x PI 127826, IPA-5 x LA 1777, e Santa Clara x LA 716.

Using the partial diallel methodology, interspecific hybrids of tomato were obtained, in order to study the general and specific combining abilities (GCA and SCA, respectively) between two groups of Lycopersicon spp. Seven characteristics of tomato resistance to Tuta absoluta were evaluated. Significant differences regarding the majority of the evaluated traits were observed. Based on GCA, the genotypes Ângela, Santa Clara, LA 716 and LA 1777 are the most indicated to be used in a breeding program to improve the tomato resistance to T. absoluta. The best hybrids, considering SCA and heterosis, were Ângela x PI 126445, Ângela x PI 127826, IPA-5 x LA 1777 and Santa Clara x LA 716.

Avaliou-se a divergência genética de acessos de taro pertencentes ao Banco de Germoplasma de Hortaliças da UFV por meio dos caracteres morfo-qualitativos de inflorescências. O experimento foi conduzido a campo em Viçosa, de setembro/2000 a julho/2001. Utilizou-se o delineamento experimental de blocos casualizados, com cinco repetições e 36 tratamentos (clones), dos quais apenas 11 acessos (BGH 5920, BGH 5926, BGH 5927, BGH 6087, BGH 6089, BGH 6091, BGH 6093, BGH 6094, BGH 6136, BGH 6306 e BGH 6606) apresentaram florescimento espontâneo, passíveis de serem avaliados. A proporção entre o apêndice estéril e porção masculina foi em média de 1,02, variando de 0,4 (BGH 6136) a 1,4 (BGH 6087). A inflorescência é circundada por uma espata cuja coloração da parte superior (CL) varia do amarelo claro, com ou sem a presença de manchas vermelhas, ao amarelo alaranjado. A cor da porção inferior da espata, contendo as flores femininas (tubo da inflorescência), varia do verde, com ou sem raias ou manchas escuras a púrpura. A espata, na antese, apresenta-se na forma aplanada (BGH 5920, BGH 5926, BGH 6091, BGH 6093, BGH 6094 e BGH 6306) ou encapuchada (BGH 5927, BGH 6087, BGH 6089, BGH 6136 e BGH 6606), com a porção masculina exposta ou envolta, respectivamente. A cor da haste das inflorescências (pedúnculo) variou do verde claro ao púrpuro, com proporção entre comprimentos do pedúnculo e da inflorescência (PCPI) média de 1,8, variando de 1,1 (BGH 5927) a 2,3 (BGH 6089). As inflorescências saem em número de 1 a 5 por axila foliar (NIAF) e apresentam de 1 a 2 ramalhetes florais por planta (NRFP). Os acessos de taro, agrupados pelo método de Tocher, formaram quatro grupos: I (BGH 5920, BGH 6091, BGH 6093, BGH 6094, BGH 5926, BGH 6606 e BGH 6087), II (BGH 6089 e BGH 6306), III (BGH 6136) e IV (BGH 5927). Com base na dispersão dos últimos componentes principais, as variáveis NRFP, CL, PCPI e NIAF, demonstraram ser de pouca importância para a descrição da variabilidade de inflorescências de taro.

The genetic diversity of taro of the Germoplasm Bank of the Universidade Federal de Viçosa, Brazil, was evaluated, by analyzing morphological and quality characteristics of the inflorescence. Plants were grown from 19/09/00 to 13/07/01. Field plots were arranged in a randomized block design with five replicates containing 36 treatments (clones), in which only 11 accesses (BGH 5920, BGH 5926, BGH 5927, BGH 6087, BGH 6089, BGH 6091, BGH 6093, BGH 6094, BGH 6136, BGH 6306 and BGH 6606) flowered spontaneously. The ratio between sterile appendage and male portion was on average 1.02, varying from 0.4 (BGH 6136) to 1.4 (BGH 6087). The inflorescence is surrounded by a spathe with light yellow color at the upper part (LC), with or without spots of red, or yellow-orange color. The bottom portion of the spathe which contains the female flowers (inflorescence tube) varied from green, containing or not strips or spots dark to purple color. At anthesis, the spathe shows flat format (BGH 5920, BGH 5926, BGH 6091, BGH 6093, BGH 6094 and BGH 6306) or hooded (BGH 5927, BGH 6087, BGH 6089, BGH 6136 and BGH 6606), with the male portion exposed or enclosed, respectively. The color of flower stalk varied from pale green to purplish, and ratio between total and inflorescence stalk length (LSLIR) average was 1.8, varying from 1.1 (BGH 5927) to 2.3 (BGH 6089). Number of inflorescences (NI) ranged from 1 to 5 per leaf axis, composing 1 to 2 floral clusters per plant (NFCP). Based on flower morphology the accesses formed four groups by Tocher method: I (BGH 5920, BGH 6091, BGH 6093, BGH 6094, BGH 5926, BGH 6606 and BGH 6087), II (BGH 6089, BGH 6306), III (BGH 6136) and (BGH 5927). Based on dispersion analysis from the last main components, the variables LC, LSLIR, NI and NFCP, showed little influence on the variability description of the inflorescence.

A divergência genética (D²) entre cinco acessos de berinjela foi estimada para avaliar a eficiência da diversidade na predição do desempenho dos híbridos respectivos. Os acessos PI 206472 e 'Campineira' foram os mais similares, enquanto 'Long Green' e PI 206472 foram os mais divergentes. A associação entre divergência genética dos genitores e desempenho dos híbridos foi analisada por três métodos, apresentando os seguintes resultados: 1) correlações de Pearson (rP) e Spearman (rS): a divergência (D²), mostrou estar linearmente associada ao desempenho médio dos híbridos para o caráter número médio de frutos por planta ( rP = 0,71 e rS = 0,636, P < 0,05) e inversamente relacionada para produção de frutos (g/planta) (rP = - 0,687, P < 0,05); 2) separação em classes de cruzamentos divergentes: mostrou-se promissora, pois dois híbridos selecionados (PI 206472 x 'Florida Market' e 'Campineira' x 'Florida Market') ocuparam segunda e a quarta posição na classificação das médias, respectivamente; 3) método da classificação dupla: considerado eficiente, pois selecionou o cruzamento PI 206472 x 'Florida Market', que obteve a segunda posição na classificação das médias, superando os híbridos 'Nápoli' e 'Super F100', os quais são cultivados comercialmente.

The genetic divergence (D²) among five accessions of eggplant was estimated to evaluate the efficiency of this divergence at predicting the performance of corresponding hybrids. The closest related accessions were PI 206472 and 'Campineira' whilst 'Long Green' and PI 206472 were the most divergent. The association between hybrid performance and genetic divergence of parents was analysed by three methods: 1) Pearson's (rP) and Spearman's (rS) correlation: genetic divergence (D²) was found to be linearly related to hybrid performance of mean fruit number per plant (rP = 0.71 and rS = 0.636, P < 0.05) and inversely related to fruit yield (rP = - 0.687, P < 0.05); 2) Divergence of cross classes: This found to be successful because two selected hybrids (PI 206472 x 'Florida Market', 'Campineira' x 'Florida Market') reached 2nd and 4th place on the rank of means respectively; 3) Method of double rank: This was found to be efficient since it allowed the selection of the cross PI 206472 x 'Florida Market', which reached 2nd place on the rank of means, overcoming the commercial hybrids 'Nápoli' and 'Super F100'.