Susceptibility and physiological responses of Jatropha curcas accessions to broad mite infestation

The broad mite Polyphagotarsonemus latus is a key pest of physic nut (Jatropha curcas L.). The purpose of this study was to identify physic nut accessions that are less susceptible to P. latus, in support of the breeding program of J. curcas. We first evaluated population growth rate and injury symptoms of P. latus on different J. curcas accessions and then carried out physiological analyses on P. latus-infested and uninfested accessions. From the germplasm bank of the Federal University of Viçosa, 15 physic nut accessions with high seed oil content, with different genetic background, were tested. The following traits were evaluated: instantaneous population growth rate of P. latus (r ᵢ ), injury symptoms, relative leaf water content, specific leaf area, gas exchange, photosynthetic pigments, nitrogen and biomass of the aerial part. Significant differences were observed for P. latus population growth rate and injury symptoms among accessions. A positive correlation between P. latus growth rate and injury was found. The UFVJC72 accession stood out as the more resistant, considering P. latus growth rate and injury symptoms, compared with most accessions. Physiological responses did not vary among accessions, but did between infested and uninfested plants. In P. latus-infested plants, net photosynthesis was on average 50.5 % lower than in uninfested plants, whereas stomatal conductance and transpiration decreased by 46.2 and 51.6 %, respectively.