Abstract Bulk sampling and subsequent DNA fingerprinting are applied to obtain estimated allelic frequency data and unveil population structure for outbreeding species. We developed ‘Gametes Simulator’, a routine to simulate gametes from allelic frequencies of unlinked loci, which enables the analysis of population structure through Bayesian analysis. Based on the allelic frequencies in the populations, the software simulates the alleles per population in the right proportions and assigns one allele per marker to each gamete following Mendel’s laws that govern gametogenesis.

RESUMO A mancha bacteriana do tomateiro é causada por quatro espécies de Xanthomonas, sendo Xanthomonas vesicatoria raça T2 a predominante no Uruguai. O manejo químico e cultural desta doença não tem sido suficiente para o seu controle; portanto, o melhoramento genético para gerar genótipos resistentes é uma estratégia importante que deve ser incluído para contribuir no manejo integrado desta doença. O objetivo do presente trabalho foi identificar fontes de resistência à mancha bacteriana foliar raça T2 do tomateiro para indústria. Doze genótipos foram avaliados no campo em 2010 e 2011. As plantas foram inoculadas com uma suspensão da bactéria (108 cfu/mL) aos 15 dias depois do transplante. O período de incubação, a severidade da doença e a percentagem dos frutos com sintomas foram determinados. Não houve diferença no período de incubação entre os genótipos. O genótipo 'Hawaii 7981' teve o menor valor de severidade nas folhas, seguido da cultivar 'Loica'. As linhagens (derivadas de 'Loica'), LB97, LB99, LB60 e LB76 e a cultivar 'Ohio 8245' tiveram um nível intermédio de severidade nas folhas, ao passo que 'H9997', 'Cuyano', LB85 e 'NUN6011' apresentaram severidades mais altas. As diferenças entre os genótipos no nível de severidade da doença foram consistentes entre os anos, porém, a incidência nos frutos foi mais variável. Junto à 'Hawaii7981', 'Loica' e 'Ohio 8245' foram identificados como novas fontes de resistência parcial à mancha bacteriana raça T2.

ABSTRACT Bacterial leaf spot of tomato is caused by four Xanthomonas species, among which Xanthomonas vesicatoria race T2 predominates in Uruguay. Difficulties in integrated disease management and the rapid spread of the pathogen led to investigations of genetic resistance. This study aimed to identify resistance sources to bacterial leaf spot race T2 in tomato for processing. Twelve genotypes were evaluated under field conditions in 2010 and 2011. Plants were spray-inoculated with a suspension of bacteria (108 cfu/mL) 15 days after transplantation. Incubation period, disease severity on leaves, and the percentage of fruits with symptoms at harvest were determined. The incubation period did not differ among the genotypes. The genotype 'Hawaii 7981' had the lowest leaf severity on the leaves, followed by 'Loica'. The lines (derived from the cultivar 'Loica') LB97, LB99, LB60, and LB76, and the cultivar 'Ohio 8245' showed intermediate levels of severity on leaves, whereas 'H9997', 'Cuyano', LB85, and 'NUN6011' presented higher severities. The differences in disease severity of the leaves were similar over the years, while incidence of symptoms in fruit was more variable. Next to 'Hawaii 7981', the cultivars 'Loica' and 'Ohio 8245' were identified as new sources of partial resistance to bacterial spot race T2.

This research analysed the response of onion (Allium cepa) and A. fistulosum against Fusarium oxysporum f. sp. cepae (Foc) isolates and the associated changes in peroxidase, β-1,3-glucanase and chitinase activities. The response of A. cepa and A. fistulosum at different stages of seedling development were also evaluated. Several seedling tests were performed, and disease symptoms were evaluated 12-14 days after inoculation. Allium fistulosum behaved as more resistant than A. cepa cultivars by exposition to the most aggressive Foc isolates at sowing date. Increased levels of peroxidase and glucanase activities were found in the A. cepa and A. fistulosum seedlings exposed to the pathogen, and were positively correlated with disease symptoms. For chitinase activity, this correlation was found only for A. cepa. Two peroxidase isoforms were found to be specific for A. fistulosum roots after inoculation and could be involved in resistance. The inoculation at 7, 14 and 42 days after sowing showed that both host species were resistant to Foc, proving that onion susceptibility decreased promptly after germination . However, an increase in peroxidase and glucanase activities in 7-and 14-day-old inoculated seedling was detected only for A. cepa, suggesting an earlier acquisition of resistance in A. fistulosum.

Foram avaliados variabilidade, herdabilidade e correlações de caracteres agronômicos em uma variedade crioula de cebola (Allium cepa L.) e linhas S1derivadas após uma geração de autofecundação. Para produzir linhas S1foram selecionados bulbos por forma, cor e número de cascas. Cinquenta e uma linhas S1e a população original foram avaliados em blocos incompletos casualizados. Houve variabilidade para caracteres quantitativos e qualitativos. As linhas S1diferiram significativamente entre si, apresentando segregação transgressiva para número e comprimento de folhas, índice de bulbificação, peso e diâmetro de bulbo e conteúdo de matéria seca. As variâncias dentro das linhas S1foram maiores do que entre elas, para todos os caracteres. Cor de bulbo e número de cascas responderam à seleção. Matéria seca e sólidos solúveis foram altamente correlacionados, com herdabilidades de 52,6% e 36,1%, respectivamente. As linhas S1permitiram expressão da variação genética e identificação dos melhores genótipos para caracteres agronômicos de interesse.

This study assessed variability, heritability and correlations of agronomic traits in an onion (Allium cepa L.) landrace and derived S1lines after a single selfing generation. Bulbs used to develop S1lines were selected for shape, colour and high number of skins. Fifty-one S1lines and the original population were evaluated using an incomplete random block design. The original population and S1lines were highly diverse for quantitative and qualitative traits. S1lines were significantly different, with transgressive segregation for number and maximum leaf length, bulbing index, bulb weight, diameter, and dry matter content. Variances within S1lines were greater than among S1lines for all traits. Bulb colour and number of skins responded to selection. Heritabilities for dry matter and soluble solids were 52.6% and 36.1% respectively. Both traits were highly correlated. The development of S1lines allowed the expression of genetic variation and the identification of better genotypes for agronomic traits of interest.

La zanahoria (Daucus carota L.) es el cuarto rubro hortícola del país. La introducción de cultivares comerciales importados que poseen mejor calidad comercial que las poblaciones locales (PL) ha provocado la pérdida de la diversidad en los materiales genéticos locales. Sin embargo, poblaciones locales continúan bajo cultivo y en el interés de productores. La zanahoria del país o criolla (semilla de origen local) se utiliza para siembras de verano, por su precocidad y adaptación a temperaturas altas. En este trabajo se estudió el comportamiento de poblaciones locales y poblaciones mejoradas, en diferentes fechas de siembra y diferentes sitios en la zona sur del Uruguay. Los trabajos se realizaron durante 2007, 2008 y 2009. Se incluyeron los cultivares «Kuroda» y «Brasilia» como controles. En el Análisis de Componentes Principales, los rendimientos comerciales y totales y los indicadores de calidad por color y contenido de carotenos fueron las variables que más diferenciaron el comportamiento de las poblaciones y de los sitios. Los efectos año (clima) y fecha de siembra explicaron las mayores diferencias entre las poblaciones en los sitios. Para siembras de marzo (final del verano) existieron diferencias significativas de los rendimientos totales y comerciales en la interacción poblaciones por año y sitios por año, pero no interacción sitio por población. La PL Rodríguez y la selección mejorada CRS se destacaron por sus rendimientos en los tres años. Los experimentos sembrados en noviembre (comienzo del verano) no mostraron diferencias en el rendimiento entre poblaciones, pero sí entre sitios y entre años, como consecuencia de la intensa sequía del verano 2008-09.

Carrot (Daucus carota L.) is the fourth vegetable crop in Uruguay. Introduction of imported commercial cultivars with improved root quality caused losses in genetic diversity in local genetic material (PL). However, local landraces are maintained under cultivation and in the interest of growers.The zanahoria del país o criolla (landraces known as ‘carrot of the country’) are used for summer sowings because of their earliness and adaptation to high temperatures. This research studied productive behaviour of collected landraces and improved selections in experiments carried out in different sowing dates during summer, and different locations in South Uruguay. Experiments were done during 2007, 2008 and 2009. Cultivars ‘Kuroda’ and ‘Brasilia’ were included as controls. After performing Principal Component Analysis, marketable yield, total yield, and root color traits were the variables better explaining the differences between landraces and/or cultivars and locations. Year and sowing date effects were responsible for the largest variations among experiments. For experiments sown in March (ending summer), marketable and total yields not significantly differ between landraces and/or cultivars in the interaction locations for years and populations for years, but the interaction landrace location was not significant. PL Rodríguez and the improved CRS population yielded high during the three years. For experiments sown in November (early summer), marketable and total yields did not significantly differ between landraces and/or cultivars, but did differ between locations and years because of a severe drought in the summer 2008-09.

El mildiú causado por Peronospora destructor constituye una de las enfermedades de mayor importancia económica en la producción de cebolla. El objetivo de este trabajo fue identificar fuentes de resistencia en el germoplasma local de cebolla. Se realizaron ensayos a campo en 2007 y 2008 en los que se evaluaron en total 40 materiales genéticos. La incidencia de P. destructor se evaluó semanalmente, se ajustó una ecuación logística a los datos y se calculó el Área debajo de la Curva de Progreso de la Enfermedad (AUDPC). En 2007, el germoplasma local mostró diversidad en la incidencia de la enfermedad (3 a 99%), en la severidad (7 a 40% del área foliar afectada) y en el AUDPC. En 2008, los materiales evaluados también mostraron diferencias, aunque de menor magnitud. Se encontró relación entre el ciclo fenológico y la resistencia. El grupo de accesiones de día largo presentó mayor resistencia que los grupos de día intermedio y de día corto. Esto podría ser el resultado de factores de resistencia específicos presentes en el germoplasma de día largo, o de diferencias fisiológicas relacionadas al estado de desarrollo que condicionan la susceptibilidad al patógeno. En 2008, la evolución de la enfermedad fue muy variable. La incidencia de P. destructor cayó bruscamente en una evaluación, y subió a la semana siguiente hasta 100% de las plantas para varias accesiones. La diversidad observada en la respuesta a P. destructor confirma el potencial del germoplasma local para ser usado como fuente de resistencia en el mejoramiento de cebolla.

Downy Mildew (DM) caused by Peronospora destructor is one of the most economically important diseases in onion production. This research aimed to identify sources of resistance to DM in local onion germplasm. Field trials were conducted in 2007 and 2008 in order to evaluate a total of 40 genetic materials. The incidence of P. destructor was assessed weekly, a logistic equation was adjusted to the data, and the Area Under Disease Progress Curve (AUDPC) was calculated. In 2007, local germplasm showed differences in the proportion of diseased plants (3 to 99%), in severity (7 to 40% of total leaf area was affected) and AUDPC. In 2008, the materials tested showed differences as well, but smaller than in 2007. Resistance and phenological cycle were related. The group of long day accessions showed higher resistance than the groups with intermediate and short-day accessions. This behavior could involve specific resistance factors present in the germplasm of long day, or could be the result of physiological differences related to the stage of development that determine susceptibility to the pathogen. In 2008, evolution of disease was very variable. The incidence of P. destructor fell sharply on an assessment, and the following week rose to 100% of the plants for several accessions. Diversity observed in the response to P. destructor supports the potential value of local germplasm to be used as source of resistance in onion improvement.