Belowground Chemical Interactions: An Insight Into Host-Specific Behavior of Globodera spp. Hatched in Root Exudates From Potato and Its Wild Relative, Solanum sisymbriifolium

Understanding belowground chemical interactions between plant roots and plant-parasitic nematodes is immensely important for sustainable crop production and soilborne pest management. Due to metabolic diversity and ever-changing dynamics of root exudate composition, the impact of only certain molecules, such as nematode hatching factors, repellents, and attractants, has been examined in detail. Root exudates are a rich source of biologically active compounds, which plants use to shape their ecological interactions. However, the impact of these compounds on nematode parasitic behavior is poorly understood. In this study, we specifically address this knowledge gap in two cyst nematodes, Globodera pallida, a potato cyst nematode and the newly described species, Globodera ellingtonae. Globodera pallida is a devastating pest of potato (Solanum tuberosum) worldwide, whereas potato is a host for G. ellingtonae, but its pathogenicity remains to be determined. We compared the behavior of juveniles (J2s) hatched in response to root exudates from a susceptible potato cv. Desirée, a resistant potato cv. Innovator, and an immune trap crop Solanum sisymbriifolium (litchi tomato – a wild potato relative). Root secretions from S. sisymbriifolium greatly reduced the infection rate on a susceptible host for both Globodera spp. Juvenile motility was also significantly influenced in a host-dependent manner. However, reproduction on a susceptible host from juveniles hatched in S. sisymbriifolium root exudates was not affected, nor was the number of encysted eggs from progeny cysts. Transcriptome analysis by using RNA-sequencing (RNA-seq) revealed the molecular basis of root exudate-mediated modulation of nematode behavior. Differentially expressed genes are grouped into two major categories: genes showing characteristics of effectors and genes involved in stress responses and xenobiotic metabolism. To our knowledge, this is the first study that shows genome-wide root exudate-specific transcriptional changes in hatched preparasitic juveniles of plant-parasitic nematodes. This research provides a better understanding of the correlation between exudates from different plants and their impact on nematode behavior prior to the root invasion and supports the hypothesis that root exudates play an important role in plant-nematode interactions.

Effect of steroidal glycoalkaloids on hatch and reproduction of the potato cyst nematode Globodera pallida

Steroidal glycoalkaloids (SGAs) are phytoanticipins found in solanaceous crops that act as the first line of chemical defense against pathogen attacks. Solanum sisymbriifolium, a trap crop for potato cyst nematodes, has been shown to effectively reduce populations of Globodera pallida. Solanum sisymbriifolium contains α- solamargine and other solasodine type glycoalkaloids that may contribute to plant defenses. The current study evaluated the influence of solanaceous SGAs on G. pallida hatch, development, and reproduction. Exposure to α- solamargine and α- solamarine reduced G. pallida hatch by 65 % and 87 % respectively. Exposure of G. pallida cysts with the glycoalkaloids α- solamargine and solasodine significantly reduced infection in susceptible potato Russet Burbank by 98 and 94 % compared to the control. Exposure of cysts to either solasodine or solamargine significantly reduced reproduction of G. pallida on Russet Burbank by 99 % compared to the control. The study demonstrated the deleterious effect of SGAs on G. pallida hatch, infection, and reproduction.

Evaluation of Nutrient Composition of Ripe and Unripe Fruits of Solanum sisymbriifolium

Introduction: Solanum sisymbriifolium or lychee tomato is a small, viscid, and prickly wild shrub native to South America, widely distributed throughout Bangladesh. Although roots and other aerial parts of this plant are traditionally used for treating various ailments, much work has not yet been done to elucidate its nutritional and economic importance of the edible fruit of this medicinal plant. Therefore, to explore the nutritional value as a food source, the proximate value and mineral content of ripe and unripe fruit of S. sisymbriifolium were assessed in this study. Materials and methods: AOAC methods have been followed to determine the proximate content, while the analysis of the mineral content has been done by using standard analytical methods. Result and Discussion: This study investigated proximate values (moisture, ash, crude fiber, crude protein, and lipid) and selected mineral contents- magnesium (Mg), phosphorus (P), calcium (Ca), sodium (Na), iron (Fe), and potassium (K) of ripe and unripe fruits of Solanum sisymbriifolium using standard analytical methods. Compared to other minerals, Mg was present in higher concentrations in both ripe and unripe fruits. The concentration of Fe in unripe (0.013 mg/100g) and ripe fruit (0.024mg/100g) was the lowest. Although proximate compositions were variable between ripe and unripe fruits, only Ca was found in higher amount in the unripe fruit (08.91 mg/100g) than the ripe fruit (06.73 mg/100g) among all the other tested minerals which makes it a more preferable option for consumption. Conclusion: The unripe and ripe fruits (preferably) of Solanum sisymbriifolium could be introduced as a functional food in the community for health promotion.

Solanum linnaeanum and Solanum sisymbriifolium as a sustainable strategy for the management of Meloidogyne chitwoodi

Root-knot nematodes (RKN), Meloidogyne spp., are important crop pests that cause severe losses in crop production worldwide, reducing both productivity and crop quality. Meloidogyne chitwoodi Golden, O'Bannon, Santo & Finley, 1980 is considered a quarantine organism by the European and Mediterranean Plant Protection Organization (EPPO) causing damage in tomato and potato crops. The development of nonchemical and sustainable management strategies to reduce nematode damage is crucial. The resistance of Solanum linnaeanum Hepper & P.-M.L. Jaeger and S. sisymbriifolium Lamarck cv. Sis 6001 to M. chitwoodi was evaluated based on gall index (GI), the Bridge & Page (1980) rating chart and reproduction factor (RF). Both plant species were resistant to M. chitwoodi. Solanum linnaeanum had an average of 519 small root swellings/plant, with 45% adult nematodes inside the roots, all males. Solanum sisymbriifolium had GI ≤ 2 and RF ≤ 1 with a high percentage (69%) of nematodes inside the roots that did not develop beyond the sexually undifferentiated second-stage. The use of S. linnaeanum as a new source of resistance is a good alternative for the control of RKN in the quest to develop nonchemical and sustainable management strategies to protect crops.

The need for new approaches for management of potato cyst nematodes: the view from the Rhineland-Palatinate.

Potato is an important crop throughout Europe and especially in Germany where potatoes are grown on over 250,000 hectares. The production of potato worldwide is negatively affected by the presence of the golden and the white potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida. The two species originated in South America. PCN is present with restricted distribution in all counties in Germany where potato is produced and these infestations are strictly regulated. Both species are present and often in mixed populations. Potato yield and overall production is negatively impacted by both species of PCN from planting to harvest, but there are differences in importance within the country and on crop type. This chapter discusses the economic importance, host range, distribution, symptoms of damage, biology and life cycle, integrated nematode management (including the use of nematicides, resistant cultivars and rotation), and interactions with other nematodes and pathogens, of PCN. Results are also summarized of field trials conducted between 2010 and 2017 to compare the efficacy of resistant cultivars and nematicide Nemathorin 10G with the alternative control techniques biofumigation and sowing of Solanum sisymbriifolium that has PCN suppressive activity.