SEE IF A GARLIC EXTRACT CAN PREVENT CROWN GALL IN ROSE AND TOMATO PLANTS.

• ABSTRACT

  Crown gall disease causes great economic losses worldwide by reducing crop yields and increasing susceptibility to opportunistic pathogens. The anti-malarial Artesunate which is a derivative of artemisinin from Artemisia annua leaf and Garlic extracts known for their inhibitory and cytotoxic effects on the proliferation of human and animal tumor cells were investigated on rapidly dividing plant cells in Agrobacterium tumefaciens-induced crown gall tumor of tomato (Solanum lycopersicum) to determine their effects.   A survey of selected flower farms in Gafan, Kadawa and Kukumi villages in Kano State showed a crown gall prevalence ranging from 0.1% to 65%. Allium sativum (Garlic extract) phytochemical screening indicated the presence of terpenoids, flavonoids, alkaloids, saponins, glycosides, phenols, and tannins. Agrobacterium tumefaciens colonies used in testing the antibacterial effect of the extracts was isolated from crushed crown galls and purified through their growth in Congo red YEMA medium and yeast peptone glucose agar. The colonies were authenticated biochemically by Gram staining, motility test, citrate utilization, catalase production, urease production and ketolactose test. From the results of this research,  Allium sativum extracts are promising biocontrols for crown gall in roses. Farmers are recommended to continue with integrated crown gall control methods and pursue plant extracts as an alternative. The performance of Artemisia annua extracts compared well with that of conventional copper hydroxide and is therefore the better option.

  CHAPTER ONE

  INTRODUCTION

        1.1       Background Information

  Crown gall disease, caused by Agrobacterium tumefaciens which is found worldwide, is the most challenging disease to control (Collinge et al 2022). The bacteria affects species belonging to over ninety-three plant families including apples, pears, cherries, apricots, grapes, tomatoes, sweet pepper, and chrysanthemums (Ade-Ogunnowo et al 2017; Kado 2002). Many bactericides have been used against crown gall and only copper compounds produce good results. The result of copper compounds is seldom satisfactory owing to the pathogen resistance and the phytotoxicity reported in many plant species (Aeni et al 2014). Crown gall is caused by bacteria that are released when a gall becomes moist or when an earlier gall decomposes. These bacteria can survive in the soil for many years. Fresh wounds or abrasions on susceptible plants—many of which are caused by pruning, freeze injury, soil insects, cultivation, and other potential plant-damaging factors—or other sources of infection are where the disease enters the plant.

  The application of synthetic fungicides remains the most effective method to control postharvest pathogens. However, their use is becoming increasingly restricted internationally due to health concerns and consumers’ requests for safe and natural alternatives  (Nxumalo, et al 2021). Extracts from medicinal plants such as ginger have proven to be effective in controlling postharvest pathogens of crops and increased their shelf life when used as a substitute for synthetic chemicals(Nxumalo, et al 2021). The application of medicinal plant extracts could be a useful alternative to synthetic chemicals in the postharvest protection and preservation of horticultural crops (Nxumalo, et al 2021).

        1.2       Statement of the problem

  The global sustainability agenda is increasing the demand for a reduction in inputs into agricultural production while maintaining the profitable yield of quality products. Plant diseases are a major constraint for both yield and product quality, but often tools for their control are ineffective or lacking (Collinge et al, 2022). Many crops undergo various physiological and biochemical changes that lead to undesirable physiological disorders, decay, and subsequent economic losses during storage. Crown gall disease causes great economic losses worldwide by reducing crop yields and increasing susceptibility to opportunistic pathogens (Ade-Ogunnowo et al 2017).

  Since plant antimicrobials degrade naturally and do not build up in the environment, they have no negative effects on the ozone layer and do not pollute soil or water. The fact that plant antimicrobials have different mechanisms of action from conventional drugs and do not contribute to disease resistance is vital for disease resistance management (Joseph and Sujatha, 2012; Hernandez et al., 2013). In order to manage bacterial and fungal infections in vegetables and flowers, plant extracts have been employed widely (Pavela, 2014; Pavela, 2016). Plant extracts have emerged as a viable option in the control of crop diseases due to the drawbacks of conventional agrochemicals and the potency of plant phytochemicals. Extracts are safe for the environment and non-toxic to good bacteria.

  The absence of chemical data and positive controls, along with difficulties in formulation and commercialization, have prevented the broad use of botanical pesticides (Joseph and Sujatha, 2012). A further difficulty is a requirement for large-scale extract production for the commercial-scale flower industry.

        1.3       Research Questions

  • Is crown gall disease prevalent in different varieties of roses in selected farms in Nigeria?
  • Which methods do the selected flower farms in Nigeria use to control crown gall disease?
  • Do Allium sativum extracts contain secondary metabolites responsible for the control of crown gall?
  • Do Allium sativum extracts inhibit the growth of Agrobacterium tumefaciens in vitro and in vivo?

  1.4   Study Objectives

  • To determine the prevalence of crown gall disease in different varieties of selected flower farms in Nigeria through a field survey.
  • To determine various methods used to control crown gall disease in selected flower farms in Nigeria.

  (iii)To determine the secondary metabolites present in  Allium sativum extracts.

   

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