Biological Effectiveness of Plant Polyphenols under Greenhouse Conditions, Against Wilt and Root Rot Complex of Chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) production is constantly compromised by a complex of pathogens which cause wilt and root rot (WRR). Therefore, biological control and organic products have regained great importance in the last few years. In this work, polyphenols were obtained from ethanolic extracts through the ultrasound-microwave assisted technique from the plant species chinese privet leaves (Ligustrum lucidum) and moringa leaves (Moringa oleifera). A qualitative analysis through reverse phase high-performance liquid chromatography electrospray ionization mass spectrometry (RP-HPLC-ESI-MS) was conducted, so that their biological effectiveness under greenhouse conditions was determined by each group of polyphenols against Fusarium oxysporum f. sp. ciceris, Fusarium solani, and Macrophomina phaseolina which comprise the wilt and root rot complex. A complete randomized block design was established with three blocks and five treatments with nine replications each. Treatments were: Polyphenols of Ligustrum lucidum, polyphenols of Moringa oleifera, the fungicide Benomyl, the inoculated check, and the untreated check. The analysis of variance was performed and mean comparison with Duncan`s multiple range test (0.05). The results indicate that all groups of polyphenol had in their chemical composition, some compounds of known microbial activity, such as hydroxycinnamic acid, flavones, anthocyanins, catechins, and alkyphenols. Under greenhouse conditions, plants that had the lowest incidence and severity of the disease, were those treated with polyphenols from L. lucidum with 66% incidence, and were statistically different to the rest of the treatments.

The Effect of Water Stress on Total-Phenolic Content of Barley

Little is known about the relation between water stress and the accumulation of phenolics in plant tissues. The present study aimed to investigate the effect of water stress and maturation on the production of total-phenolics (TP) by four barley (Hordeum vulgare L.) varieties (‘Manel’, ‘Martin’, ‘Rihane’, ‘Espérance’). During three phenological stages (S-8, S-10.5, S-11), following Feekes scale, whole barley plants were pulled out of the field and separated into roots, stems, and leaves. Water extracts were prepared from plant parts and their TP contents were determined by spectrophotometer. To determine periods of water deficit (WD) at field, climatic characterization of the region was carried out. TP accumulated in barley plant and its parts under the influence of water deficit essentially at S8, which coincided with barley spring growth. However, TP content decreased when WD became more pronounced at the following stages. This response may be explained, partially by the biosynthesis of lignin from free phenols when the plant approached maturity. Results suggest that water stress stimulates the synthesis and accumulation of TP in barley tissues during active growth periods (spring growth) at S-8. This response doesn’t persist until the critical periods of WD where barley maturity favors a decrease in TP content for all plant parts. Regardless of growth stage and WD, barley accumulates preferentially phenolics in above-ground plant parts. The evolution of phenolic accumulation under water stress showed the same trends for the tested barley varieties, indicating a genetic control of phenolic production and their partitioning across plant parts.