Identification of pathogenic fungi and preliminary screening for resistance in Jatropha curcas L. germplasm

Jatropha curcas L. (jatropha) is a perennial undomesticated plant with a high untapped potential for sustainable production of food, biofuels and biomass-based products. The identification of resistance sources in the germplasm is important to develop improved varieties. In order to characterize presence of pathogens in multiple production sites, leaf samples showing symptoms of diseases were collected in Argentina, India, and Cameroon. Samples were used for DNA extraction and species identification through PCR, sequencing and BLAST searches. The identified fungal isolates were inoculated onto healthy plants using the agar block method. Re-isolation from symptomatic plants with subsequent DNA extraction and molecular identification confirmed pathogenicity of six species: Phoma herbarum, Diaporthe phaseolorum, Nigrospora sphaerica, Gibberella moniliformis, Alternaria alternata, and Fusarium sp. The identified pathogens were used to screen for resistance in a set of 20 jatropha genotypes. One genotype showed resistance to P. herbarum, seven to N. sphaerica, five to D. phaseolorum and one to G. moniliformis. Only three genotypes showed resistance to more than one pathogen. The sources of resistance and their respective level need to be validated in field experiments.