Stigma receptivity and anther dehiscence in ornamental pepper

<div><p>ABSTRACT The objective of this study was to evaluate stigma receptivity and anther dehiscence in three floral development stages in F3 population of ornamental pepper (Capsicum annuum). A total of 162 plants (81 of purple corolla and 81 of white corolla) were used in this study. To analyze the stigma receptivity and anther dehiscence, three floral stages were analyzed: bud, pre-anthesis, and open flower. For each stage, 33 flowers of each phenotypic class were collected. The receptivity of the stigma was detected by dripping hydrogen peroxide solution (3%). For the evaluation of the level of receptivity, scores of 0 to 3 were assigned, varying according to the bubbles percentage found on the stigmatic surface. Scores of 1 to 5 were assigned for the reference of the amount of pollen released by the stamens. The data were subjected to analysis of variance (p≤0.05) following a 2x3 factorial scheme: two classes of flower colors and three development stages, with 33 replicates (flowers) with later separation of means by Tukey’s test at the same probability level. For the analysis of divergence, the data were clustered according to Tocher’s method based on generalized Mahalanobis distance. Despite the not significant differences between the means for pollen dehiscence of both flower colors, the purple flowers presented higher stigma receptivity than the white ones. The ornamental pepper flowers displayed stigma receptivity since the bud phase, but the highest level of receptivity was observed after anthesis. Anther dehiscence prevailed after anthesis of the flowers regardless of color, and the presence of pollen grains was superior after anthesis. For the manual crossing, the buds at pre-anthesis phase are the most indicated irrespective of the color, as they show high stigma receptivity and greater ease at handling.</p></div

Reação em campo à murcha bacteriana de cultivares de tomate em Roraima Bacterial wilt resistance in tomato cultivars in Roraima, Brazil

A murcha bacteriana causada por Ralstonia solanacearum (Smith) é a doença bacteriana mais importante do tomateiro na Região Norte do Brasil. Os objetivos deste trabalho foram avaliar o nível de resistência de cultivares de tomate, avaliar o progresso da murcha bacteriana nesses genótipos a fim de conhecer o comportamento da doença nos diferentes estádios de desenvolvimento da cultura, para auxiliar no manejo da epidemia, e determinar a época crítica para o desenvolvimento da doença nessas cultivares nas condições de Roraima. Os experimentos foram conduzidos em um campo naturalmente infestado com a biovar 1 de Rasltonia solanacearum, por dois anos. A área tinha um histórico de quatro anos de plantios sucessivos com plantas de tomate suscetíveis à murcha bacteriana, e as perdas alcançando até 100%. Para condução do experimento foram utilizadas mudas das cultivares Majestade, Nemonetta, Carmen, Liliane, Santa Clara, Sensação, San Vito, Gaúcho Melhorado, Hector e Laura. Foram feitas seis avaliações do número de tomateiros que apresentavam murcha irreversível e/ou morte durante o ciclo da cultura. Foram determinadas as variáveis área abaixo da curva de progresso da doença (AACPD) e a taxa de progresso da doença (r), incidência média (Y50), incidência máxima (Ymáx) e a incidência final da doença. Os valores de AACPD e da variável r para a cultivar Majestade foram menores que para as demais, demonstrando que houve menor incidência de plantas doentes nesta cultivar, indicando resistência. Embora o nível de resistência apresentado por esta cultivar não seja muito elevado, o cultivo da mesma é recomendável e viável para o plantio no Estado de Roraima, especialmente considerando-se os altos preços do tomate, que são adquiridos de outras regiões produtoras no país, embora somente esta resistência não garanta, sozinha, o controle adequado da doença, sendo necessárias outras medidas de controle associadas.<br>The bacterial wilt caused by Ralstonia solanacearum is the most important bacterial disease of tomato in the Brazilian North Region. The objectives of this study were to evaluate (1) the resistance level of ten tomato cultivars; (2) the progress of bacterial wilt in these genotypes in order to know the disease behavior in different stages of development of the crop, and (3) determine the critical time to disease development in these cultivars, in Roraima. The experiment was carried out in a field naturally infested with biovar 1 of R. solanacearum, during two years. The area was infested by cultivating susceptible tomato plants to bacterial wilt. The cvs. Majestade, Nemonetta, Carmen, Liliane, Santa Clara, Sensação, San Vito, Gaúcho Melhorado, Hector and Laura were cultivated in the infested field. Six disease incidence evaluations were done in seven plants with irreversible wilt and/or death during the crop cycle. The following variables were determined: area under the disease progress curve (AUPDC) and the progress rate (r), mean incidence (Y50), maximum incidence (Ymax) and the final incidence of the disease. The values of AUDPC and the variable r to 'Majestade' were the lowest, although the level of resistance shown by this cultivar was not very high. Therefore, 'Majestade' is recommended for planting in the State of Roraima, especially considering the high prices of tomatoes, which are purchased from other regions in the country. However, only the level of resistance of 'Majestade' is not sufficient for disease control, being necessary other control measures