Silicon and Nitrate Differentially Modulate the Symbiotic Performances of Healthy and Virus-Infected Bradyrhizobium-nodulated Cowpea (Vigna unguiculata), Yardlong Bean (V. unguiculata subsp. sesquipedalis) and Mung Bean (V. radiata)

Abstract

The effects of 2 mM silicon (Si) and 10 mM KNO3 (N)—prime signals for plant resistance to pathogens—were analyzed in healthy and Cowpea chlorotic mottle virus (CCMV) or Cowpea mild mottle virus (CMMV)-infected Bradyrhizobium-nodulated cowpea, yardlong bean and mung bean plants. In healthy plants of the three Vigna taxa, nodulation and growth were promoted in the order of Si + N > N > Si > controls. In the case of healthy cowpea and yardlong bean, the addition of Si and N decreased ureide and α-amino acids (AA) contents in the nodules and leaves in the order of Si + N> N > Si > controls. On the other hand, the addition of N arrested the deleterious effects of CCMV or CMMV infections on growth and nodulation in the three Vigna taxa. However, the addition of Si or Si + N hindered growth and nodulation in the CCMV- or CMMV-infected cowpea and yardlong bean, causing a massive accumulation of ureides in the leaves and nodules. Nevertheless, the AA content in leaves and nodules of CCMV- or CMMV-infected cowpea and yardlong bean was promoted by Si but reduced to minimum by Si + N. These results contrasted to the counteracting effects of Si or Si + N in the CCMV- and CMMV-infected mung bean via enhanced growth, nodulation and levels of ureide and AA in the leaves and nodules. Together, these observations suggest the fertilization with Si + N exclusively in virus-free cowpea and yardlong bean crops. However, Si + N fertilization must be encouraged in virus-endangered mung bean crops to enhance growth, nodulation and N-metabolism. It is noteworthy to see the enhanced nodulation of the three Vigna taxa in the presence of 10 mM KNO3.

Is it time to include legumes in plant silicon research?

“…Other studies addressing the impacts of silicon on legumes (listed in Table 2) also report how silicon supplementation increased nodule dry biomass in two different cultivars of soybean (Steiner, Zuffo, Bush, & Santos, 2018) and in three different Vigna plants (Izaguirre‐Mayoral, Brito, Baral, & Garrido, 2017). In addition, Kurdali, Al‐Chammaa, and Al‐Ain (2018) showed that the effects of silicon on root nodulation and nitrogen fixation were more profound under salinity and/or water stress in Sesbania legume but relatively minor in the absence of such stress.…”

Silicon Improves Soil Environment and Promotes Crop Growth under Compound Irrigation via Brackish Water and Reclaimed Water

“…Studies have confirmed that silicon fertilizer is beneficial for plant growth and development and can enhance plant biomass and yield. For example, silicon fertilizer can improve photosynthesis [9,10], increase crop yield by enhancing gas exchange properties and the chlorophyll content in leaves to reduce oxidative damage [11,12], improve root colonization [13], and promote the growth and symbiosis of beneficial microorganisms [14]. Moreover, silicon fertilizer can reduce the harm of insects and pathogens [15]; improve the nutrient utilization efficiency of P, Ca, K, etc.…”

Silicon supplementation and jasmonate activation synergistically increase phenolic defences against a legume herbivore

“…Si supplementation frequently increases nodule abundance, nitrogenase activity (indicative of increased N-fixation) and concentrations of nitrogenous compounds (protein and amino acids) in Medicago spp. and other legumes (Nelwamondo & Dakora 1999;Izaguirre-Mayoral et al 2017;Putra et al 2022), especially when plants are under stress (e.g. Al Murad & Muneer 2022).…”