ResumoA resistência genética constitui-se em alternativa sustentável para o controle de doenças em culturas agrícolas, sendo esta, no entanto, dependente da avaliação de populações naturais ou tradicionais visando à ampliação da base genética. Este trabalho relata a avaliação fenotípica de 24 progênies de mamoeiro, oriundas de genótipos crioulos, cultivados por pequenos agricultores no sul do Estado do Espírito Santo. Avaliaram-se características associadas à resistência à pinta-preta, importante doença desta cultura, causada pelo fungo Asperisporium caricae. Para fins comparativos, foram incluídas uma variedade resistente ('Maradol') e uma suscetível ('Golden') à pinta-preta. Pelos parâmetros genéticos estimados, concluiu-se que na população estudada há variabilidade genética quanto à resistência à pinta-preta suficiente para indicar a seleção recorrente como método de melhoramento.Palavras-chave: Asperisporium caricae, Carica papaya, herdabilidade, resistência genética, variabilidade genética. Pathometry, genetic parameters and papaya progenies reaction to black-spot disease AbstractGenetic resistance is a sustainable alternative to control diseases in crops, being indispensable the enlargement of the genetic base to introduce new resistance genes on developing cultivars. This study reports the phenotypic evaluation of 24 papaya progenies, originated of landraces cultivated for small farmers in south of the Espírito Santo State, Brazil. Characteristics related to the resistance to black-spot disease, induced by the fungi Asperisporium caricae were evaluated. For comparison one genotype resistant ('Maradol') and one susceptible ('Golden') to black-spot disease were included on the study. Based on the genetic parameters estimated, the studied population has genetic variability for resistance to black spot diseases appropriates for use of recurrent selection as crop breeding method.

further root deepening in WS conditions. Under WS P7 maintained higher net photosynthesis values, stomatal conductance, and transpiration, than L75. Additionally, L75 exhibited a lower (i.e., more negative) carbon isotope composition value than P7 under WS, confirming a lower stomatal aperture in L75. In summary, besides leaf greenness, traits related to leaf photosynthetic status, and stomatal conductance were shown to be good indicators of the agronomic performance of popcorn under water constraint.

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Landrace genotypes present sources of genes for adaptation, rusticity and resistance to diseases and environmental stress. This study evaluated the potential of landrace papaya genotypes in contributing to phoma-spot resistance genes. The experiment was a randomized block design with six replications consisted of 24 half-sib progenies of dioecious papaya -which segregated for sex. Only plants with female flowers were evaluated. We used mixed models to estimate variance components and the genetic value of landraces to incidence and severity of phoma-spot. Heritability estimates and selective accuracy demonstrated a favorable situation to the selection of resistant progenies ,especially 'STA-02', 'STA-04', 'STA-05', 'STA-06', 'STA-07', 'STA-11', 'STA-12', 'STA-16', 'STA-21' and 'STA-22', which showed negative values of additive genetic effects for both incidence and severity of phoma-spot.

ABSTRACT. Lasiodiplodia theobromae is a plant pathogen with a worldwide distribution, with low host specificity, causing stem cankers, dieback diseases, and fruit rot in several species of plants. In coconut, this pathogen is reported as the etiological agent of "coconut leaf blight" (CLB) disease, causing several losses in fruit production. The CLB is an important disease for this crop in Brazil. In our study, we used a phylogeographic approach through the molecular characterization of the translation elongation factor 1-α (TEF1-α) to elucidate the pathogen distribution in Brazil and other countries, besides, search information about diversity sources of this pathogen in coconut palm tree at Brazilian northern, northeast, and southeast. We found that L. theobromae diversity is within populations (locations), and populations that are located closest to the center of the tropical zone have more variability as Central Africa, Brazilian Southeast, and Northeast. The widespread distribution could be in part related with long-distance dispersal via global trade of plants and plant products. The entrance route of L. theobromae in Brazil probably occurred from Africa route and not occurred once. In Brazil, the diversity of this pathogen in coconut tree could be linked to two agents of selection: high host diversity (in Northeast) and distinct management measures adopted in Southeast. These different sources of selection, mainly the mutations, could be one of the reasons that we found distinct reactions to "coconut leaf blight" chemical control in these regions.

A resistência genética constitui alternativa sustentável para o controle do oídio. Objetivando indicar possíveis combinações híbridas que contribuam para a redução da severidade de oídio em folha de mamoeiro, foi realizado um cruzamento dialé-lico envolvendo oito genótipos, sendo quatro do grupo 'Solo' e quatro do grupo 'Formosa'. Os 56 híbridos (F1's e recíprocos) juntamente com seus genitores foram avaliados em blocos casualizados com quatro repetições. A severidade do oídio na folha foi quantificada em março e maio de 2010, respectivamente, aos 11 e 13 meses após o plantio. Com a média de cada tratamento foram estimadas as capacidades geral e específica de combinação. Assim, considerando as estimativas da capacidade combinatória obtidas com base na média das duas avaliações, as melhores combinações para os genitores avaliados quanto à severidade do oídio foram 'Maradol x Waimanalo', 'Maradol x Sunrise Solo 72/12', 'JS 12-4 x São Mateus', 'Sekati x Waimanalo', 'Sekati x Golden', 'Sekati x Sunrise Solo 72/12', 'Sekati x São Mateus', 'Waimanalo x São Mateus' e 'Golden x São Mateus'. Os resultados evidenciam ainda a possibilidade de obtenção de híbridos com potencial para redução da severidade do oídio provenientes de cruzamentos entre genótipos dos grupos 'Solo' e 'Formosa' e também em cruzamentos dentro do grupo 'Solo'. Palavras-chave: Streptopodium caricae, Carica papaya, hibridação.Combining ability for resistance to powdery-mildew in papaya AbstractGenetic resistance represents a sustainable alternative to control powdery-mildew in papaya crop. Diallelic crosses were performed among eight papaya genotypes, belonging to 'Solo' and 'Formosa' heterotic groups, four from each one with aiming to indicate possible hybrid combinations that contribute to reducing the severity of powdery-mildew on leaf. The 56 hybrid combinations (F1's and reciprocals) along with their parents were evaluated in a randomized complete block design with four replications. Powdery-mildew severity on leaves was measured in March and May 2010, respectively, at 11 and 13 months after planting. The general and specific combining ability were estimated from the severity data.

The objective of this study was to evaluate the effects of additive and non-additive genes on the efficiency of nitrogen (N) use and N responsiveness in inbred popcorn lines. The parents, hybrids and reciprocal crosses were evaluated in a 10x10 triple lattice design at two sites and two levels of N availability. To establish different N levels in the two experiments, fertilization was carried out at sowing, according to soil analysis reports. However, for the experiments with ideal nitrogen availability, N was sidedressed according to the crop requirement, whereas for the N-poor experiments sidedressing consisted of 30% of that applied in the N-rich environment. Two indices were evaluated, the Harmonic Mean of the Relative Performance (HMRP) and Agronomic Efficiency under Low Nitrogen Availability (AELN), both based on grain yield at both N levels. Both additive and non-additive gene effects were important for selection for N-use efficiency. Moreover, there was allelic complementarity between the lines and a reciprocal effect for N-use efficiency, indicating the importance of the choice of the parents used as male or female. The best hybrids were obtained from inbred popcorn lines with contrasting N-use efficiency and N responsiveness.

Guard cell (GC) length proved to be efficient in sorting diploids from haploids in doubled haploid development in maize (Zea mays L). It compensates for the weakness of widely used R1-nj marker approach that showed low reliability in haploids identification from tropical genotypes. Guard cell length differs between haploid and diploid plants, and these differences were evaluated in the progeny of three different induction crosses obtained using Krasnodar haploid inducer. Epidermal impressions of the abaxial surface of leaves removed from the second, third, and fourth nodes (from base to apex) were collected and measured using an optical microscope. This was also conducted on the flowering phenotype. Guard cell length varied according to germplasm source, leaf stage, and ploidy level. Mean GC length ranged from 23.67 to 33.82 μm in haploids, and from 36.1 to 41.25 μm in diploids. Based on these differences in GC length at any of the chosen leaf stages (second, third, or fourth), diploid and haploid maize plants were successfully classified. Classification efficiency was found to be more closely related to germplasm source than leaf stage. Comparing GC length according to phenotype (haploid or diploid), GC limits for classification as a diploid plant (threshold points) were estimated and ranged from 29.74 to 34.49 μm, depending on germplasm source. The highest false discovery rate was 2.93% and false negative rate was 15.06%, indicating that classification based on GC length was reliable.