Virulence and Reproductive Fitness of Meloidogyne paranaensis Field Populations in Coffee Genotypes.

The aim of this study was to characterize Meloidogyne paranaensis populations collected from infested coffee crops. Methodologies used to characterize the 11 studied populations from municipalities in Paraná and Minas Gerais States involved the morphological analysis of perineal patterns, biochemical analysis by isozyme electrophoresis, sequencing of internal transcribes spacer 1 (ITS-1) and D2/D3 ribosomal DNA (rDNA) regions, reproductive fitness, and virulence characterization in coffee genotypes. Morphological evaluations showed the existence of variation between populations, although the majority of them showed typical perineal patterns. The biochemical identification was based on α-esterase isozyme analyses and resulted in the appearance of three distinct profiles: P1 (typical), P2 (atypical), and a nondescribed profile, P2b. BLAST of the ITS-1 and D2/D3 rDNA regions indicated homology (>95%) with other sequences deposited in GenBank. For reproductive fitness and virulence characterization, 13 coffee genotypes (5 Coffea arabica and 8 C. canephora) were inoculated with 11 M. paranaensis populations. Variation in the reproductive fitness of populations was observed for cultivar Mundo Novo, a genotype without resistance genes, and variation in the virulence of populations was observed in genotypes carrying resistance genes. Three populations exhibited virulence combined with high reproductive fitness, while one showed virulence with low reproductive fitness. Some hosts were resistant to 11 populations, while one of the hosts was resistant to only one population, indicating the presence of different resistance genes. Nevertheless, no relationship was observed between the origin of population and their variations in perineal patterns, esterase profiles, phylogeny, or reproductive fitness in coffee genotypes, or between the different characterizations, although differences were observed within each characteristic.

Arabica coffee fruits phenology assessed through degree days, precipitation, and solar radiation exposure on a daily basis.

Knowledge regarding reproductive cycle duration is important in terms of scheduling harvests and estimating coffee cultivars adaptability. Nine Coffea arabica cultivars were evaluated during two successive reproductive cycles. Dates of occurrence of the major blossoms, and the green and ripe fruits, on 64 branches for each cultivar, were registered during each reproductive cycle. These dates were used to calculate the duration of the fruit development (blossom to green) and ripening (green to ripe) phases, the quantities of degree days, precipitation, and solar radiation accumulated throughout each phase, and also degree days, precipitation, and radiation on a daily basis, all of which are novelties in coffee research. The differences between cultivars and reproductive cycles were tested by ANOVA. Cultivars were grouped in clusters according to the above-cited variables. Principally, the daily quantities of degree days and precipitation determined the differences between reproductive cycles and coffee cultivars during development phases. Early and very early cultivars accumulated high numbers of degree days.day-1, in periods of relatively good water availability, with high exposure to solar radiation. Late cultivars accumulated less degree days.day-1 and were exposed to lower amounts of daily solar radiation and longer periods of water scarcity. Regarding the fruit ripening phase, cultivars were principally distinguished by degree days and solar radiation on a daily basis. Two of the coffee cultivars were classified or confirmed as early and very early and another three as late and very late. One cultivar, Siriema, displayed an interesting conjugation of early and intermediate characteristics.

Porta enxertos de café robusta resistentes aos nematóides Meloidogyne paranaensis e M. incognita raças 1 e 2 / Robusta coffee rootstocks resistants to Meloidogyne paranaensis and M. incognita races 1 and 2

No Estado do Paraná, os nematóides mais danosos para o café são Meloidogyne paranaensis e M. incognita raças 1 e 2. A enxertia de cultivares suscetíveis de Coffea arabica sobre C. canephora resistentes tem sido bem sucedida, especialmente com o porta-enxerto Apoatã IAC-2258, porém existe segregação para a resistência. O objetivo deste trabalho foi identificar cafeeiros de C. canephora var. robusta com resistência simultânea aos nematóides M. parnaensis e M. incognita raças 1 e 2. Avaliaram-se 24 genótipos de C. canephora na metodologia de Taylor, no delineamento em blocos ao acaso com três repetições e parcelas de 30 plantas. Como testemunha suscetível utilizou-se a cultivar Mundo Novo IAC 376-4. As variáveis avaliadas foram incidência dos nematóides e volumes radicular. Os níveis de resistência encontrados entre as plantas foram resistente, moderadamente resistente e suscetível. Foram identificados seis genótipos do porta-enxerto C. canephora var. robusta com resistência, provavelmente em homozigoze, para os nematóides M. paranaensis, M. incognita raça 1 e M. incognita raça 2, todos com bom volume radicular. As plantas mães desses seis melhores genótipos serão propagadas vegetativamente e usadas para formar campo de sementes de cultivares porta-enxertos.

The Meloidogyne paranaensis and M. incognita races 1 and 2 are the most pathogenic root knotnematodes of coffee crop in Paraná state, Brazil. The use of susceptible arabica cultivars on resistantrootstock robusta cultivars, especially cultivar Apoatã IAC-2258 of Coffea canephora var. robusta, hasbeen successful, but there are segregations to susceptible ones. The aim of this research was to identify C. canephora var. robusta coffee trees with simultaneous resistance to M. paranaensis, M. incognitaraces 1 and 2. Twenty-four C. canephora genotypes were evaluated using Taylor ́s evaluation method,conducted in randomized blocks design with three replications and 30 plants per plot. The cultivarMundo Novo IAC 376-4 was used as susceptible standard. The variables evaluated were nematodesincidence and root volume. The resistance levels founded among plants were resistant, moderatelyresistant and susceptible. Six genotypes of C. canephora var. robusta with simultaneous resistance,probably in homozygous, to M. paranaensis, M. incognita race 1 and M. incognita race 2 were found,all with good root volume. The mother plants of these six better treatments will be vegetatively propagatedand used to begin seed production of rootstock cultivars

Avaliação da viabilidade de sementes de café por exsudatos / Evaluation of the coffee seeds viability by exudates

Existe uma grande necessidade de testes que possibilitem uma avaliação rápida e segura da qualidade das sementes. O objetivo deste trabalho foi estimar o coeficiente de correlação existente entre a germinação de sementes de café e a liberação de exsudato marrom. Utilizaram-se placas de Petri e papel-toalha umedecido onde foram colocadas as sementes. Os materiais foram obtidos de lotes de sementes com vários níveis de envelhecimento. Foi utilizado o delineamento em blocos ao acaso com 7 repetições e parcelas constituídas de 10 sementes. Obtiveram-se correlações negativas altas e significativas a 1 entre a germinação e vigor germinativo com a liberação de exsudato marrom. As análises de variância indicaram diferenças significativas na germinação entre sementes de diferentes graus de envelhecimento em relação aos exsudatos marrons. A vantagem desta técnica é avaliar o poder germinativo em poucas horas, sem o uso de mão-de-obra especializada e equipamentos caros.

A quick evaluation of the germination quality of the seeds is very important for coffee growers. The aimof this research was to estimate the correlation coefficient between the germination and the liberation ofbrown exudates of coffee seeds with different times after preparation. Petri dishes and humid filter wereused to place the seeds. The seeds were obtained from lots of seeds with several aging degrees. Theexperimental design used was in randomized blocks with seven replications and plots constituted by 10seeds. High negative correlations (P=0.01) were obtained between the germination and germinativevigour with the liberation of brown exudates at different times. The variance analyses indicated significantdifferences to germination among seeds of different aging degrees at different evaluation times. Theadvantage of this technique is to evaluate the germinative quality in six or twelve hours, without the useof specialized labour and expensive equipments