The biology of Fusarium oxysporum f. sp. gladioli, causal agent of corm rot of Gladiolus corms

Authors Avatar

Chapter Two

The biology of Fusarium oxysporum f. sp. gladioli, causal agent of corm rot of Gladiolus corms

Abstract

Gladiolus corm rots disease caused by F.oxysporum f.sp. gladioli results in severe crop lossess in many parts of the world. The problem is increasing owing to the lack understanding of the physiological and ecological factors affecting on of F.oxysporum f.sp. gladioli. Different physiological factors as Temperature, Ph, Nutrition, Water activity were employed to understand their effects on F. oxysporum f. sp. gladioli. Results showed that, the strains responded diversely to the different Physiological factors. The optimum temperature for G010 was 20-250 C, and 8 pH. However the optimum growth for 640, 160 strains were 25-300 C, and pH 4. PDA was the best suitable media for all isolates.

Briefly there are differences between F.oxysporum f. sp. gladioli strains and they are differing in their needs. Those differences could affect on the pathogenity.  

Introduction

Most known fungal species are strictly saprophytic, with less than 10% of the more or less 100.000known fungal species able to colonize plants Carlile et al. (2001). Plant parasitic fungi have dominated the living plants as an abundant source of nutrients ( Mendgen et al., 1996). But there is a different level of specialization in plant-fungal interaction. The first group include involves true pathogens that rely on living plants but can grow outside of their hosts. The second group the opportunistic parasites which enter plants through wounds or new hair roots. These species are usually low virulence (Jackson and Taylor 1996).

Fusarium oxysporum causes wilt diseases in a wide variety of economically important plants and cause a destructive loss in the crops production (Gordon 1997). Managing Fusarium wilt disease is a achieved through chemical soil fumigation and resistant cultivars. Now there are available broad spectrums of biocides used to fumigate soil before planting as Captan, Benomiel and other commercial varieties ( Fravel et al., 2003)  But they are have a negative impact on the environment . The environmentally save method is the use of BCAs.

But resistance breeding are very difficult when no dominant gene is known (Fravel et al., 2003). Further more the pathogen can overcome the plant resistance. Virulent races of F.oxysporum f.sp. ciceris have undermined the importance of resistant cultivars of chickenpea ( Haware and Nene 1982).

Fusarium oxysporum pathogensis

Pathogensis describes the complete process of disease development in the host, from initial infection to production of symptoms (Lucas 1998). During the initial stage of the interaction, fungal pathogens must sense stimuli from the plant and respond with appropriate morphogenic and biochemical changes (Gordon 1997).Effects caused by pathogens on plants are almost entirely the result of biochemical reaction taking place between substances secreted by the pathogen and those present in or produced by the plant. During pathogensis the fungus penetrate in defence barriers that plant cell walls comprise of ( Mengden et al., 1996).The pathogenic fungi secrete a mixture of hydrolytic enzymes including cutinase, cellulase, pectinase and proteases ( Knogge 1996).After penetration the fungus produce toxins that manipulate plant physiology ( Walton 1994).

Factors Enhance F.oxysporum pathogenesis

Temperature

F.oxysporum optimal growth was found to be between 25 and 28O C Carlile et al. (2001).The growth of the Fusarium wilt pathogeneses disease was maximized at 28 C and inhibited above 33 C, and not favoured below 17 C. Jackson et al. (1990) recorded the relationship between substrate temperature and disease intensity, when they found wilt symptoms in carnations did not developed at extreme high or low temperature a little colonisation was found at 14 C. More severe sympotoms of wilt chickpea were found at 25 and 30 C than at 10, 15, and 20 ( Bhatti and Kraft 1992). Fusarium wilt of carnation was developed at 85% shade Carlile et al. (2001).

Join now!

Harling et al., 1988 suggested that temperature alter the balance between the host plant and Fusarium wilt pathogen.The effect of temperature on wilt occurrence may vary in different pathosystems( Ben-Yephet and Shtienberg 1997).  Brake et al., 1995 found that the impact of temperature was on plant growth not on the pathogen. F.oxysporum f. sp. cubense is present in some tropical regions, it severly affects banana in the subtrobics, indicating that temperature may have an important influence on disease development ( Ploetz et al., 1990).

Ph

Increasing soil pH has appositive effect on Fusarium wilt disease reduction (Jons and Woltz ...

This is a preview of the whole essay