Biochemical analysis of induced resistance in chickpea against broomrape (Orobanche foetida) by rhizobia inoculation

This study examined the capacity of Rhizobium sp. strain PchAZM to reduce parasitism of chickpea by Orobanche foetida under greenhouse conditions, and assessed the relative impact of rhizobia on the expression of chickpea defense response against broomrape. Growth chamber experiments using Petri dishes revealed that rhizobia infection on chickpea roots reduced broomrape seed germination, and restricted the broomrape attachment to host roots while retarding tubercle formation and development by the parasite. In pot experiments, chickpea roots inoculated with rhizobia reduced the total number of broomrape by up to 90%. Broomrape necrosis was observed both before and after parasite attachment to inoculated chickpea roots in Petri dishes and pot experiments. Reduction in infection was accompanied by enhanced levels of the defence-related enzymes phenylalanine ammonia lyase (PAL) and peroxidase (POX). Increased levels of phenolics were recorded in the roots of rhizobia-inoculated plants grown in the presence of broomrape. The results suggest that rhizobia could be used for protection of chickpea against O. foetida

Potential of Rhizobia in Improving Nitrogen Fixation and Yields of Legumes

Strong demand for food requires specific efforts by researchers involved in the agricultural sector to develop means for sufficient production. While, agriculture today faces challenges such as soil fertility loss, climate change and increased attacks of pathogens and pests. The production of sufficient quantities in a sustainable and healthy farming system is based on environmentally friendly approaches such as the use of biofertilizers, biopesticides and the return of crop residues. The multiplicity of beneficial effects of soil microorganisms, particularly plant growth promotion (PGP), highlights the need to further strengthen the research and its use in modern agriculture. Rhizobia are considered as PGP comes in symbiosis with legumes taking advantage of nutrients from plant root exudates. When interacting with legumes, rhizobia help in increased plant growth through enriching nutrients by nitrogen fixation, solubilizing phosphates and producing phytohormones, and rhizobia can increase plants’ protection by influencing the production of metabolites, improve plant defense by triggering systemic resistance induced against pests and pathogens. In addition, rhizobia contain useful variations to tolerate abiotic stresses such as extreme temperatures, pH, salinity and drought. The search for rhizobium tolerant strains is expected to improve plant growth and yield, even under a combination of constraints. This chapter summarizes the use of rhizobia in agriculture and its benefits

Impact of Nitrogen Fertilization on Fusarium Foot and Root Rot and Yield of Durum Wheat

This study investigated the influence of nitrogen fertilization on Fusarium foot and root rot. Disease index, percentage of white heads, grain yield, weight of 1000 grains and nitrogen content were evaluated in durum wheat after artificial inoculation with Fusarium culmorum under field conditions. The trial was conducted using Karim wheat cultivar during growing season 2016/17. Five nitrogen rates, 0, 50, 100,150 and 200 kg N/ha were evaluated. Nitrogen supply at higher rates (150 and 200 kg/ha) significantly increased disease index, the percentage of white heads, the grain yield, the weight of 1000 grains and nitrogen content. These results suggest that high amounts of nitrogen fertilization may increase infection of wheat by Fusarium foot and root rot disease by influencing the plant physiology

Bacteria-inducing legume nodules involved in the improvement of plant growth, health and nutrition

Bacteria-inducing legume nodules are known as rhizobia and belong to the class Alphaproteobacteria and Betaproteobacteria. They promote the growth and nutrition of their respective legume hosts through atmospheric nitrogen fixation which takes place in the nodules induced in their roots or stems. In addition, rhizobia have other plant growth-promoting mechanisms, mainly solubilization of phosphate and production of indoleacetic acid, ACC deaminase and siderophores. Some of these mechanisms have been reported for strains of rhizobia which are also able to promote the growth of several nonlegumes, such as cereals, oilseeds and vegetables. Less studied are the mechanisms that have the rhizobia to promote the plant health; however, these bacteria are able to exert biocontrol of some phytopathogens and to induce the plant resistance. In this chapter, we revised the available data about the ability of the legume nodule-inducing bacteria for improving the plant growth, health and nutrition of both legumes and nonlegumes. These data showed that rhizobia meet all the requirements of sustainable agriculture to be used as bio-inoculants allowing the total or partial replacement of chemicals used for fertilization or protection of crops

Growth promotion and protection against Orobanche foetida of chickpea (Cicer aerietinum) by two Rhizobium strains under greenhouse conditions

Fetid broomrape (Orobanche foetida Poir.) is a chlorophyll lacking holoparasite that subsists on the roots of plants and causes significant damage to the culture of leguminous plants particularly chickpea (Cicer aerietinum L.). The investigation was done about potential of Rhizobium strains for biological control of O. foetida using a commercial chickpea cultivar (Béja 1) and different Rhizobium strains. Firstly, benefit of bacterial inoculation on plant growth and efficiency in N-incorporation were demonstrated with four isolates, Azm, Bj, Sd.N2 and Sd.N1. Rhizobium strains were investigated for their ability to control O. foetida using pot and Petri-dish experiments. Inoculation of chickpeas with two (Azm and Bj) of the Rhizobium strains induced a significant decrease in O. foetida seed germination and in the number of tubercles on chickpea roots. Furthermore, other symptoms, including the non-penetration of the germ tube of germinated seeds into chickpea roots followed by radical browning and death of the parasite, were observed in the presence of these inoculated chickpea plants. The hypothesis that roots secrete toxic compounds related to Rhizobium inoculation is discussed.Keywords: Biological control, Rhizobium strains, Orobanche foetida, chickpea, necrotic symptomsAfrican Journal of Biotechnology Vol. 12(12), pp. 1371-137