Intercropping Systems in Wheat (Triticum sativum L.) for Insect Pests and Disease Management – A Review

Cereal crop wheat, Triticum sativum L., is an important food and feed crop that is grown all over the world. There is a complementary relationship between legumes and cereals for nitrogen resources, it was found that intercropped legumes acquire a higher amount of atmospheric nitrogen in comparison to legumes grown as an individual crop. Furthermore, both wheat and pulse intercropping give benefits in terms of minimizing pests and diseases. Intercropping not only restricts onset of pest species but also crop combinations conserves beneficial insects that can preserve the damaging pest population below the threshold level. In the current study, numerous instances were provided that show successful control of various insect pests when wheat was intercropped with mustard, Linseed, barley, mung bean, canola, and other crops. Wheat intercropping with other crops can be used as part of an integrated pest management strategy to reduce pest incidence while also increasing the number of beneficial organisms.

At the Root of Nodule Organogenesis: Conserved Regulatory Pathways Recruited by Rhizobia

The interaction between legume plants and soil bacteria rhizobia results in the formation of new organs on the plant roots, symbiotic nodules, where rhizobia fix atmospheric nitrogen. Symbiotic nodules represent a perfect model to trace how the pre-existing regulatory pathways have been recruited and modified to control the development of evolutionary “new” organs. In particular, genes involved in the early stages of lateral root development have been co-opted to regulate nodule development. Other regulatory pathways, including the players of the KNOX-cytokinin module, the homologues of the miR172-AP2 module, and the players of the systemic response to nutrient availability, have also been recruited to a unique regulatory program effectively governing symbiotic nodule development. The role of the NIN transcription factor in the recruitment of such regulatory modules to nodulation is discussed in more details.

Malate Transport and Metabolism in Nitrogen-Fixing Legume Nodules

Legumes form a symbiosis with rhizobia, a soil bacterium that allows them to access atmospheric nitrogen and deliver it to the plant for growth. Biological nitrogen fixation occurs in specialized organs, termed nodules, that develop on the legume root system and house nitrogen-fixing rhizobial bacteroids in organelle-like structures termed symbiosomes. The process is highly energetic and there is a large demand for carbon by the bacteroids. This carbon is supplied to the nodule as sucrose, which is broken down in nodule cells to organic acids, principally malate, that can then be assimilated by bacteroids. Sucrose may move through apoplastic and/or symplastic routes to the uninfected cells of the nodule or be directly metabolised at the site of import within the vascular parenchyma cells. Malate must be transported to the infected cells and then across the symbiosome membrane, where it is taken up by bacteroids through a well-characterized dct system. The dicarboxylate transporters on the infected cell and symbiosome membranes have been functionally characterized but remain unidentified. Proteomic and transcriptomic studies have revealed numerous candidates, but more work is required to characterize their function and localise the proteins in planta. GABA, which is present at high concentrations in nodules, may play a regulatory role, but this remains to be explored.

Trait–Abundance Relationships of Annual Ephemerals in Response to Nitrogen Addition in Gurbantunggut Desert

Understanding the effect of nitrogen addition on species trait–abundance relationships is one of the central focuses of community ecology and can offer us insights into the mechanisms of community assembly under atmospheric nitrogen deposition. However, few studies have focused on desert ecosystems. In this study, we measured the abundance and ecological stoichiometric traits, leaf carbon content (LCC), nitrogen content (LNC), and phosphorus content (LPC) for all annual ephemerals in all plots subjected to nitrogen addition in early spring in Gurbantunggut Desert, northern Xinjiang, China. We found a significant relationship between traits (LNC, N:P, and C:N) and abundance, indicating that ecological stoichiometry is a good proxy for explaining and predicting species abundance. We further found that significant trait–abundance relationships still existed under different nitrogen addition levels. The result suggests that trait-based niche-assembly theory plays an important role in determining species abundance under atmospheric nitrogen deposition.