Screening of wild coffee (coffea spp.) for resistance to meloidogyne incognita race 1

International audienceOne hundred and forty six cuttings representing duplicates of 73 wild accessions from 16 coffee species were evaluated for resistance to Meloidogyne incognita race 1. Five species were subdivided on the asis of geographical origin because morphological differences were previously observed. Two wellcharacterized susceptible and resistant cultivars were used as comparative controls. The experiments were conducted in a greenhouse using a clonal population of M. incognita from Brazil. The reproduction factor (RF) was used to evaluate the resistance (RF1) to the nematode infection. Plants of both controls were discriminated on the basis of RF values. Both duplicate cuttings of the wild accessions were identically classified as resistant or susceptible. Eight species displayed a resistant reaction, onespecies was considered to be susceptible, and seven species presented both susceptible and resistant accessions. Resistance to M. incognita appeared to be a more frequent character than susceptibility within the gene pool of wild coffee. These results provide coffee breeders with material whose resistance can be transferred into commercial cultivars.Ciento curaenta y seis estacas de 73 accesiones silvestres perteneciendo a 16 especies de café fueronevaluadas para su resistencia a Meloidogyne incognita raza 1. Se subdividió cinco especies según su origengeográfico en base a diferencias morfológicas previamente observadas. Los experimentos fueron realizadosen invernadero con una población clonal de M. incognita colectada en Brasil. Las resistencia ysusceptibilidad a este nematodo fueron evaluadas mediante el factor de reproducción (FR). Las plantas delos dos testigos fueron discriminadas en base a los valores del FR. Se observó siempre la mismaclasificación como resistente o susceptible de las dos estacas de cada una de las accesiones silvestresevaluadas. Ocho especies mostraron una respuesta de resistencia; una especie fue considerada comosusceptible y siete especies presentaron algunas accesiones susceptibles y otras resistentes. La resistencia aM. incognita parece ser más frecuente que el carácter de susceptibilidad dentro de la base genética de loscafetos silvestres. Los presentes resultados proveen a los fitomejoradores de café material vegetal cuyaresistencia puede ser transferida a cultivares comerciale

A high-throughput method for early screening of coffee (Coffea spp.) genotypes for resistance to root-knot nematodes (Meloidogyne spp.)

Root-knot nematodes (Meloidogyne spp.) threaten the livelihood of millions of farmers producing coffee worldwide. The use of resistant plants either as cultivars or rootstocks appears to be the single most effective method of control. A screening method was developed to evaluate large populations of plants for resistance to root-knot nematodes. Two coffee cultivars, one susceptible and the other resistant to Meloidogyne paranaensis, were grown under controlled conditions in two substrates: a commercial sieved potting compost and an inert substrate containing sand with a water-absorbent synthetic polymer. Plant growth and development and nematode multiplication were compared for two inoculation dates (2 and 8 weeks after planting) and two evaluation dates (eight and 13 weeks after inoculation). Root growth, but not nematode multiplication, was influenced by the choice of substrate. Evaluation of the differences in root weight and nematode numbers between the different cultivars, substrates and dates of inoculation suggested that an optimal condition could be defined. The best discrimination between susceptible and resistant plants was found in the experiment where inoculation occurred at 2 weeks after planting and evaluation occurred at 8 weeks after inoculation. Because the total duration of this experiment was only 3 months, high-throughput evaluation was possible, opening up new possibilities for screening large germplasm collections and studying the genetic control of root-knot nematode resistance in coffee

Near-complete genome sequences of rice yellow mottle virus isolates from Senegal

Rice yellow mottle virus in Senegal is reported here for the first time. The near-complete genomic sequences of two isolates (Se1 and Se5) were obtained. A comparison with 18 sequences from West Africa revealed a new cluster with an isolate from Gambia, located at a basal position in the phylogenetic tree

Resistance to Meloidogyne paranaensis in wild Coffea arabica

Nine accessions of wild Coffea arabica from Ethiopia were evaluated for resistance to Meloidogyne paranaensis. Two well-characterized susceptible and resistant cultivars were used as comparative controls. The experiments were conducted in a growth chamber using a clonal population of M. paranaensis (esterase phenotype P1) originating from Brazil. Resistance and susceptibility to the nematode were evaluated using the number of nematodes (eggs and J2) per plant, number of nematodes per gram of root and the reproduction factor (RF). All wild coffee accessions expressed a resistance response to M. paranaensis similar to that of the resistant control Nemaya (RF < 1.0). These results provide coffee breeders with material whose resistance can be transferred into commercial cultivars