Infection process of Fusarium oxysporum f. sp. phaseoli on resistant, intermediate and susceptible bean cultivars

Abstract

The objective of this study was to understand the infection process of Fusarium oxysporum f. sp. phaseoli (Fop) in bean cultivars classified as resistant (Manteigão Fosco 11), intermediate (VP8) and susceptible (Meia Noite). Plants of the three cultivars were inoculated at 10 days after emergence with a suspension of 1×10 6 conidia of Fop per mL. At 43 days after the inoculation, stem segments were observed with a scanner electronic microscope. The cultivars Manteigão Fosco 11 and VP8 presented an occluding material in the xylem vessels, which may have restricted tissue colonization by Fop. The resistance of bean cultivars to Fop seemed also to be explained by structural differences in the xylem tissue. Key words: Phaseolus vulgaris, Fusarium wilt, host defense.The fungus Fusarium oxysporum Schlecht. f. sp. phaseoli Kendrick & Snyder (Fop) is the causal agent of the Fusarium wilt on common beans (Phaseolus vulgaris L.) and is present in all the regions that produce beans in the world (Alves-Santos et al., 2002;Abawi & Pastor-Corrales, 1990;Schwartz & McMillan, 1989;Buruchara & Camacho, 2000). The inadequate rotation of cultures, especially in areas irrigated with central pivot, the lack of preventive measures of control of the pathogen dissemination and the increase of soil compaction made the Fusarium wilt one of the most important bean diseases in Brazil (Paula Júnior et al., 2006).The dark, thick-walled chlamydospores are the longterm survival structures in soil (Abawi & Pastor-Corrales, 1990). Management practices alone may not be enough to keep the disease in low levels of intensity. Thus, the most efficient and viable alternative for the control of this disease is the use of resistant cultivars (Abawi, 1989;Abawi & Pastor-Corrales, 1990;Paula Júnior et al., 2006).The pathogen is capable of penetrating intact root tissue, although penetration of older parts of root and hypocotyl tissue also occurs, usually through wounds or natural openings (Abawi, 1989;Dongo & Müller, 1969;Duque & Müller, 1969). After penetration, hyphae of Fop move inter-and intracellularly and invade the xylem vessels (Mace et al., 1981). The fungus is confined to xylem vessels until the later stages of disease development, although limited invasion of the adjacent tissues may occur; growth of hyphae and transportation of microconidia in the xylem vessels are observed in susceptible cultivars (Abawi, 1989). On the other hand, in resistant plants the colonization between adjacent xylem vessels is restricted, probably as a result of chemical and structural alterations (Mace et al., 1981), including vascular occlusion by the formation of gel plugs, tyloses, deposition of additional wall layers and infusion of these structures with phenols and other metabolites (Mace et al., 1981).Although there are some reports about the differences in the histopathology of stem tissues from resistant and susceptible bean cultivars infected by Fop, detailed studies that approach the infectious process in plant tissues are scarce, especially compari...

Resistance to Fusarium wilt in common bean

“…Pereira et al (2013) inoculated FOP UFV 01 in differential cultivars of beans, proposed by Woo et al (1996) and Alves-Santos et al (2002), and concluded that this isolate is a new race of the species. FOP UFV 01 inoculum was produced with PDA (potato -dextrose -agar) discs containing mycelia that were transferred to Petri dishes containing PDA.…”

“…The isolate FOP UFV 01 was collected from plants of the common bean cultivar Meia Noite with typical Fusarium wilt symptoms, in Coimbra (Minas Gerais, Brazil) (Pereira et al 2013). Pereira et al (2013) inoculated FOP UFV 01 in differential cultivars of beans, proposed by Woo et al (1996) and Alves-Santos et al (2002), and concluded that this isolate is a new race of the species.…”

“…However, Pereira et al (2013) reported that aside from wilting, the plant is affected by stunted growth in some Fop-infected bean cultivars. To assess this trait by quantifying the rate of stunted growth, plants of the same genotype are used as negative control (uninoculated), which restricts the evaluation to genotypes with high degree of uniformity (lines or hybrids).…”

Doenças e produtividade de genótipos promissores de feijão comum em Quevedo, Equador

“…As linhagens promissoras Ser-03 (8,5%), Ser-31 (10,3%), Ser-08 (11,3%) e EVG-16 (10,5%) e o cultivar crioulo Pata de paloma (10,6%), além de obter a menor intensidade da mela, também apresentaram a menor incidência da podridão (Pereira et al, 2013). Para desenvolver novas estratégias de combate a doenças, como podridão vermelha, o entendimento da biologia desses patógenos e os mecanismos moleculares de defesa do hospedeiro contra esses são cruciais (Yadeta & Thomma, 2013).…”

Fusarium species associated with grain sorghum and mungbean in Queensland

“…phaseoli invades bean plants via wounds, natural openings, or intact roots, whereby hyphae grow intracellularly in the root cortex until they reach the xylem vessels (de Borba et al, 2017). Mycelium spreads rapidly to the upper segments of susceptible plants, causing necrosis of the hypocotyl tissues and stunting (Pereira et al, 2013, de Borba et al, 2017.…”