Identification and Pathogenicity of Fusarium Spp. Isolated From Flax Roots

Abstract

even different fungi were isolated from the necrotic root tissues of infected Flax seedlings or older plants. Samples used in isolation were randomly collected from the experimental flax plots at Giza Agricultural Research Station. Fusarium spp. were isolated most frequently comprising 41.09%, while frequencies of isolation of the other fungi ranged from 1.00 to 23.97%. Regression analysis revealed that root colonization incidence (RCI) and root colonization severity (RCS) and relationship of rootcolonizating fungi of flax conformed to the linear model. According to the generated model, RCI accounted for 89.8% of the total variation in RCS. A total of 52 randomly selected isolates from infected roots were tested for pathogencity on flax cultivar Sakha 1 under greenhouse conditions. The results of pathogenicity test demonstrated that Fusarium spp. are the major causal agents of flax seedling blight as they accounted for 54% of the pathogenic isolates in the test. A total of 103 monosporic Fusarium isolates were randomly colleced from eight governorates and identified to species level. F.oxysporum (63.60%) and F.solani (27.35%) were the most predominant species. Other species were F.moniliforme (3.88%), F.lateritium(1.04%), F.semitectum (0.66%) and unidentified Fusarium spp. (3.49%). RCI and RCS relationship of rootcolonizing fusaria of flax conformed to the linear model. According to the generated model, RCI accounted for 75.3% of the total variation in RCS. Of the 103 isolates, a random sample of 32 isolates were tested for pthogenicity on seedlings of flax cultivar Giza 10 under greenhouse conditions. The results of the pathogenicity test showed that 66.67% of pathogenic isolates belonged to F.oxysporum, while 33.33% belonged to F.solani. The high frequencies F.oxysporum and F.solani and their ability to cause considerable losses during seedling stage, strongly suggest that they are the most important fusaria involved in the etiology of seedling blight and root rot of flax in Egypt. Grouping the isolates of F.oxysporum, F.solani, and F.lateritium by cluster analysis, based on their virulence patterns was neither related to their geographic origins nor to species.

Fungi Involved in Damping-off of Cotton Seedlings and Their Differential Pathogenicity on Two Cotton Cultivars

“…Once mixed, the bottles were autoclaved for 2h. The secluded inoculum was aseptically placed in the bottle and allowed to colonize on the sorghum for 2 weeks after being obtained from a one-week-old culture on PDA (Aly et al, 1996).…”

“…The only species capable of invading and killing cotton seedlings were F. oxysporum and F. moniliforme; the rest were categorized as wound parasites or saprophytes. Aly et al (1996) found Fusarium spp. in 97.7% of 88 tested samples taken from naturally infected cotton roots in various Egyptian governorates, and also documented that F. oxysporum and F. moniliforme were significant pathogens in the etiology of cotton damping-off in Egypt.…”

“…phaseolina has an extensive dispersion in Egyptian soil, and is easily and commonly obtained from cotton roots, mainly through the late stage of the growing season. For example, M. phaseolina was obtained from 37.5% of 88 examined samples from 12 different governorates (Aly et al, 1996). A negative correlation (r= −0.85, P< 0.01) has been observed between disease incidence and yield (Turini et al, 2000).…”

Pathogenicity assay of some soil-borne fungi isolated from cotton seedlings

“…phaseolina is widely distributed on Egyptian ground, and it is easily and frequently Late in the growth season, cotton roots were isolated. Thus, when (Aly et al, 1996) collected and assayed M. phaseolina was recovered from 37.5 percent of the samples analysed from 88 samples of infected cotton roots from 12 Egyptian governorates. However, it was not clear whether this variation represented usable resistance in a breeding program.…”

“…F. solani isolates, on the other hand, were nearly all extremely pathogenic (Nelson et al, 1997). Fusarium was commonly isolated from damping-off-infected cotton seedlings in cotton (Aly et al, 1996;El Samawaty, 1999). F. solani isolates from cotton were found to be pathogenic in 83 percent of cases (Abd-Elsalam et al, 2006).…”