Sampling plans for pest mites on physic nut

The starting point for generating a pest control decision-making system is a conventional sampling plan. Because the mites Polyphagotarsonemus latus and Tetranychus bastosi are among the most important pests of the physic nut (Jatropha curcas), in the present study, we aimed to establish sampling plans for these mite species on physic nut. Mite densities were monitored in 12 physic nut crops. Based on the obtained results, sampling of P. latus and T. bastosi should be performed by assessing the number of mites per cm² in 160 samples using a handheld 20× magnifying glass. The optimal sampling region for T. bastosi is the abaxial surface of the 4th most apical leaf on the branch of the middle third of the canopy. On the abaxial surface, T. bastosi should then be observed on the side parts of the middle portion of the leaf, near its edge. As for P. latus, the optimal sampling region is the abaxial surface of the 4th most apical leaf on the branch of the apical third of the canopy on the abaxial surface. Polyphagotarsonemus latus should then be assessed on the side parts of the leaf’s petiole insertion. Each sampling procedure requires 4 h and costs US$ 7.31.     

Potential of the predatory mite Amblydromalus zannoui to control pest mites on Jatropha curcas

Amblydromalus zannoui Sourassou, Sarmento and Moraes is a phytoseiid mite of the limonicus group described from central Brazil from leaves of physic nut, Jatropha curcas L. (Malpighiales: Euphorbiaceae), a plant potentially useful as a source of biofuel. This plant is often attacked by the mites Polyphagotarsonemus latus (Banks) (Prostigmata: Tarsonemidae) and Tetranychus bastosi Tuttle, Baker and Sales (Prostigmata: Tetranychidae). The objectives of this work were to evaluate the predation rate of A. zannoui on those phytophagous mites, to assess its life cycle on these prey and on pollen of Ricinus communis L. (Euphorbiaceae), and to determine its attraction to physic nut leaves infested by P. latus or T. bastosi. Amblydromalus zannoui attacked more nymphs and adults than eggs of P. latus, and more eggs and larvae than adults of T. bastosi. The life table parameters suggest that A. zannoui performs better on P. latus (r_m: 0.20, R_o: 18.77; λ: 1.23) and pollen (r_m: 0.18, R_o: 23.32, λ: 1.18). The predator seems to be attracted to plants with P. latus, but attraction was not clear cut for plants with T. bastosi. The results suggested that A. zannoui is a potential control agent to be used against P. latus on physic nut plants, and that R. communis pollen can be used as supplementary food to maintain the predator population in the absence of prey.

     

Suitability of the predatory mites Iphiseiodes zuluagai and Euseius concordis in controlling Polyphagotarsonemus latus and Tetranychus bastosi on Jatropha curcas plants in Brazil

One of the most promising plant species for biofuel production in Brazil is the physic nut Jatropha curcas. Major phytosanitary problems include the attack of two pest mite species, the broad mite Polyphagotarsonemus latus and the spider mite Tetranychus bastosi. Owing to pesticide-related problems, there is an increasing demand for sustainable environmental-friendly control methods such as biological control. In this study we evaluated the suitability of the predatory mite species Iphiseiodes zuluagai and Euseius concordis in controlling P. latus and T. bastosi on J. curcas. The number of T. bastosi killed by I. zuluagai was lower than the number of P. latus consumed. Euseius concordis preyed upon both T. bastosi and P. latus but the number of prey killed was always lower in comparison with I. zuluagai. However, P. latus and T. bastosi are suitable for the development of I. zuluagai and E. concordis as oviposition of both predators did not differ in relation to prey species. The preference of I. zuluagai for leaves of plants infested by either P. latus or T. bastosi, combined with the higher values for predation obtained by this predatory mite when fed on P. latus, compared to those values obtained by E. concordis, suggests that I. zuluagai can be more efficient than E. concordis in reducing populations of P. latus and T. bastosi under field conditions. Furthermore, we report here on the first record of predatory mites associated with P. latus and T. bastosi on native J. curcas plants in Brazil. In conclusion, we emphasize the crucial importance of predatory mites as agents of natural biological control of mite pests on J. curcas in small farms.     

Analysis of the genetic diversity of physic nut, <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. accessions using RAPD markers

A sum of 48 accessions of physic nut, Jatropha curcas L. were analyzed to determine the genetic diversity and association between geographical origin using RAPD-PCR markers. Eight primers generated a total of 92 fragments with an average of 11.5 amplicons per primer. Polymorphism percentages of J. curcas accessions for Selangor, Kelantan, and Terengganu states were 80.4, 50.0, and 58.7%, respectively, with an average of 63.04%. Jaccard’s genetic similarity co-efficient indicated the high level of genetic variation among the accessions which ranged between 0.06 and 0.81. According to UPGMA dendrogram, 48 J. curcas accessions were grouped into four major clusters at coefficient level 0.3 and accessions from same and near states or regions were found to be grouped together according to their geographical origin. Coefficient of genetic differentiation (G_st) value of J. curcas revealed that it is an outcrossing species.     

Isolation of 55 microsatellite markers for Jatropha curcas and its closely related species

Jatropha curcas L. (physic nut) is native to Central America and now naturalized widely in many tropical and subtropical areas. Microsatellite markers were isolated and characterized. Eleven out of 55 markers showed polymorphisms, and the allelic variation was investigated using 26 accessions of J. curcas collected from several provinces in Thailand. Each marker showed 2 to 5 alleles and the average polymorphic information content (PIC) was 0.49. Thirty four markers (62 %) were also successfully amplified in J. integerrima, J. gossypifolia and J. podagrica.     

Efficacy of karanjin and phorbol ester fraction against termites (Odontotermes obesus)

The non-edible oil seeds of Jatropha curcas (physic nut) and Pongamia pinnata (karanja) contain some toxic components (phorbol esters in J. curcas and karanjin in P. pinnata), which may be used as biopesticides. In this study, the active components of J. curcas and P. pinnata oil were extracted and their efficacy against the termites Odontotermes obesus (Rambur), was tested. The phorbol ester fraction of J. curcas and karanjin of P. pinnata oil were found to be effective against termites. A mortality rate of 100% was achieved in 6 h with karanjin and in 12 h with phorbol ester fraction. The LC₅₀ levels of karanjin and phorbol esters fractions were 0.038 and 0.071 g ml⁻¹, respectively, after 24 h at a 95% (0.05) confidence limit.     

Joint analysis of phenotypic and molecular diversity provides new insights on the genetic variability of the Brazilian physic nut germplasm bank

The genetic variability of the Brazilian physic nut (Jatropha curcas) germplasm bank (117 accessions) was assessed using a combination of phenotypic and molecular data. The joint dissimilarity matrix showed moderate correlation with the original matrices of phenotypic and molecular data. However, the correlation between the phenotypic dissimilarity matrix and the genotypic dissimilarity matrix was low. This finding indicated that molecular markers (RAPD and SSR) did not adequately sample the genomic regions that were relevant for phenotypic differentiation of the accessions. The dissimilarity values of the joint dissimilarity matrix were used to measure phenotypic + molecular diversity. This diversity varied from 0 to 1.29 among the 117 accessions, with an average dissimilarity among genotypes of 0.51. Joint analysis of phenotypic and molecular diversity indicated that the genetic diversity of the physic nut germplasm was 156% and 64% higher than the diversity estimated from phenotypic and molecular data, respectively. These results show that Jatropha genetic variability in Brazil is not as limited as previously thought.     

Drought stress response in Jatropha curcas: Growth and physiology

Tolerance to drought remains poorly described for Jatropha curcas accessions from different geographical and climatic origins. To address this issue we studied the response of two J. curcas accessions, one from Indonesia (wet tropical climate) and the other from Cape Verde islands (semi-arid climate). Potted seedlings (with 71 days) of both accessions were subjected to continuous well watered conditions (control) or to a drought stress period followed by re-watering. To mimic natural conditions in which drought stress develops gradually, stress was imposed progressively by reducing irrigation (10% reduction every 2 days, on a weight base), for a period of 28 days, until a field capacity of 15% (maximum stress) was achieved, followed by one week under well-watered conditions. We measured soil and plant water status, growth and biomass partitioning, leaf morphology, leaf gas exchange and chlorophyll a fluorescence. Both accessions maintained high leaf relative water content (70–80%) even at maximum stress. Net photosynthesis (A_n) was not affected by mild to moderate stress but it abruptly dropped at severe stress. This was due to reduced stomatal conductance, which showed earlier decline than A_n. Plant growth (stem elongation, leaf emergence and total leaf area) was reduced, minimizing water loss, but no significant differences were found between accessions. Drought stress did not reduce chlorophyll contents but led to reduced chlorophyll a/b. Both accessions showed fast recovery of both stomatal and photochemical parameters suggesting a good tolerance to water stress. Both J. curcas accessions showed a-dehydration-avoidant behaviour, presenting a typical water saving strategy due to strict stomatal regulation, regardless of their provenance.     

Global patterns of arthropod herbivory on an invasive plant,the physic nut (Jatropha curcas L.)

The physic nut (Jatropha curcas L.) is a multipurpose and oil‐producing shrub of Central and South American origin. Since the 15th century, this shrub has existed across tropical regions. Despite its presumed resistance to herbivores, reports show that arthropod herbivores infest it. However, no comprehensive account of arthropod herbivores, which consume the physic nut, exists. Here, we conducted a literature review that provides a comprehensive account of arthropod herbivores of the physic nut. Based on the co‐evolutionary hypothesis, we expected to find a higher herbivore of species richness and a larger proportion of native herbivores within the native range than elsewhere. As physic nut is a well‐defended plant chemically, we expected to find evidence for highest herbivory levels in plant parts that are the least defended. By the literatures review, we compiled 78 arthropod herbivores representing nine orders and from 31 families that feed on physic nut across the globe. As expected, the highest numbers of herbivores (34 species) were documented within the native range of the J. curcas and the lowest species number (21 species) in Africa. Of the 34 species in Central and South America, 94% were of native origin. Nine species were found feeding on J. curcas on more than one continent. Origins of 49% of species were from the native range of J. curcas. The highest percentage (54%) of species belonged to Hemiptera. With regard to feeding guilds, 59% of the herbivores belonged to sucking and 41% to chewing species. Forty‐one per cent of species were flower or fruit feeders, and 36% foliage feeders. We conclude that J. curcas is, despite its toxicity, vulnerable to herbivory, mainly to foliage, flower and fruit feeders.     

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta in a seasonally dry area in Kenya

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta was studied over a 10-month period in two field trials near Lake Victoria in Kenya. One plot was maintained free of mites by means of acaricide, while the other was artificially infested.The highest population density of M. tanajoa occurred during the dry season. A maximum leaf area index (LAI) of about 2 was reached at the onset of the dry season. The total leaf area of mite infested plants was reduced compared with uninfested plants during the dry spell. During the following rainy season infested plants recovered and attained the same leaf area as uninfested plants. A multiple regression model predicting the leaf area showed that 58% of the seasonal variation could be explained by plant age, soil water, and leaf injury.The net growth rate of infested plants was lower than that of uninfested plants. Maximum values of 21 (infested plants) and 49 (uninfested plants) g m^-2 week^-1 were attained at the onset of the second rainy season. No difference was found between uninfested and infested plants with respect to net assimilation rates per unit leaf area during the dry season. The net assimilation rates reached a maximum almost at the same time as the growth rates, but the infested plants peaked slightly earlier and at a lower level than the uninfested plants. M. tanajoa did not affect the relative allocation of dry matter into stems and storage roots, but the absolute allocation of dry matter declined with increasing mite injury. Thus, after 10 months the dry matter of infested plants was reduced by 29% and 21% for storage roots and stems, respectively, compared with the uninfested plants.     

Plant regeneration of non-toxic Jatropha curcas—impacts of plant growth regulators, source and type of explants

Jatropha curcas is an oil bearing species with multiple uses and considerable economic potential as a biofuel plant, however, oil and deoiled cake are toxic. A non-toxic variety of J. curcas is reported from Mexico. The present investigation explores the effects of different plant growth regulators (PGRs) viz. 6-benzyl aminopurine (BAP) or thidiazuron (TDZ) individually and in combination with indole-3-butyric acid (IBA), on regeneration from in vitro and field-grown mature leaf explants, in vitro and glasshouse-grown seedlings cotyledonary leaf explants of non-toxic J. curcas. In all the tested parameters maximum regeneration efficiency (81.07%) and the number of shoot buds per explants (20.17) was observed on 9.08 μM TDZ containing Murashige and Skoog’s (MS) medium from in vitro cotyledonary leaf explants. The regenerated shoot buds were transferred to MS medium containing 10 μM kinetin (Kn), 4.5 μM BAP and 5.5 μM α-naphthaleneacetic acid (NAA) for shoot proliferation. The proliferated shoots could be elongated on MS medium supplemented with 2.25 μM BAP and 8.5 μM IAA. Rooting was achieved when the basal cut end of elongated shoots were dipped in half strength MS liquid medium containing different concentrations and combinations of IBA, IAA and NAA for four days followed by transfer to growth regulators free half strength MS medium supplemented 0.25 mg/l activated charcoal. The rooted plants could be established in soil with more than 90% survival rate.     

Changes in leaf epicuticular wax,gas exchange and biochemistry metabolism between <Emphasis Type="Italic">Jatropha mollissima</Emphasis> and <Emphasis Type="Italic">Jatropha curcas</Emphasis> under semi-arid conditions

Jatropha curcas and Jatropha mollissima plants were evaluated under conditions of high (HSM) and low (LSM) soil moisture in a semi-arid environment, as changes in the content and concentration of epicuticular wax and the leaf metabolism which could have a relationship with drought tolerance. Besides epicuticular wax, gas exchange, antioxidant system and biochemical parameters of the photosynthetic metabolism were measured. The epicuticular wax content increased only in J. mollissima leaves 95 % under LSM, when compared with HSM conditions. Therefore, J. curcas invested less in the production of long-chain n-alkanes than did J. mollissima under LSM conditions. J. mollissima plants showed the highest CO₂ assimilation rate during the HSM period compared to J. curcas. Both species showed high stability in some leaf biochemistry products, highlighting the highest sugar content, free amino acids, total soluble protein, and photosynthetic pigments in the leaves of J. mollissima plants under both of the soil moisture conditions. Moreover, the stability and performance of the different parameters, such as morphologic variables, seem to allow J. mollissima plants to tolerate semi-arid conditions.     

Effect of Hirsutella rhossiliensis on Infection of Potato by Pratylenchus penetrans

We evaluated the ability of the nematode-pathogenic fungus Hirsutella rhossiliensis (Deuteromycotina: Hyphomycetes) to reduce root penetration and population increase of Pratylenchus penetrans on potato. Experiments were conducted at 24 C in a growth chamber. When nematodes were placed on the soil surface 8 cm from a 14-day-old potato cutting, the fungus decreased the number entering roots by 25%. To determine the effect of the fungus on population increase after the nematodes entered roots, we transplanted potato cuttings infected with P. penetrans into Hirsutella-infested and uninfested soil. After 60 days, the total number of nematodes (roots and soil) was 20 ± 4% lower in Hirsutella-infested than in uninfested soil.     

Genome-wide analysis of the terpene synthase gene family in physic nut (<Emphasis Type="Italic">Jatropha curcas</Emphasis> L.) and functional identification of six terpene synthases

Plant terpenes constitute a large class of compounds and have numerous biological roles as either primary or secondary metabolites. Terpene synthases (TPSs) play key roles on catalyzing the formation of different terpenes; they are divided into seven subfamilies based on sequence relatedness (TPSa–h). TPS-a proteins catalyze the formation of sesquiterpenes and diterpenes in plants. Physic nut (Jatropha curcas L.) is an attractive biofuel tree, but its seeds contain diterpene derivatives, which make them inedible for animals. In this study, 59 putative TPS genes (JcTPS01 to JcTPS59) were identified in the physic nut genome, and 26 belong to the TPS-a subfamily. Eight among the 26 TPS-a genes showed expression in developing seeds of physic nut in the present study. After heterologous expression of these eight genes in Escherichia coli and in vitro enzyme assays, six were shown to have TPS activities. Two (JcTPS09 and JcTPS11) catalyzed the production of diterpene casbene, which was consistent with earlier findings. The other four (JcTPS02, 23, 55, and 56) catalyzed the production of sesquiterpenes. These results may facilitate the efforts for identifying TPS genes involving the physic nut terpene synthesize.     

An efficient in planta transformation of Jatropha curcas (L.) and multiplication of transformed plants through in vivo grafting

An efficient and reproducible Agrobacterium-mediated in planta transformation was developed in Jatropha curcas. The various factors affecting J. curcas in planta transformation were optimized, including decapitation, Agrobacterium strain, pin-pricking, vacuum infiltration duration and vacuum pressure. Simple vegetative in vivo cleft grafting method was adopted in the multiplication of transformants without the aid of tissue culture. Among the various parameters evaluated, decapitated plants on pin-pricking and vacuum infiltrated at 250 mmHg for 3 min with the Agrobacterium strain EHA 105 harbouring the binary vector pGA 492 was proved to be efficient in all terms with a transformation efficiency of 62.66 %. Transgene integration was evinced by the GUS histochemical analysis, and the GUS positive plants were subjected to grafting. Putatively transformed J. curcas served as "Scion" and the wild type J. curcas plant severed as "Stock". There was no occurrence of graft rejection and the plants were then confirmed by GUS histochemical analysis, polymerase chain reaction (PCR) and Southern hybridization. Genetic stability of the grafted plants was evaluated by using randomly amplified polymorphic DNA (RAPD), marker which showed 100 % genetic stability between mother and grafted plants. Thus, an efficient in planta transformation and grafting based multiplication of J. curcas was established.