Effects of inoculum density, plant age and temperature on disease severity caused by pythiaceous fungi on several plants

Raftoyannis, Yannis; Dick, M.W.

doi:10.1007/bf02983972

Cited by 31 publications

(18 citation statements)

References 22 publications

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“…Further genetic studies will determine whether R1R2R3 and R4R5R6 in C. moschata and C. pepo, respectively, are syntenic. Deployment of R4R5R6 (from #181761-36P) in susceptible cultivar groups of C. pepo will provide oligogenic resistance against Phytophthora crown rot (Bowers and Mitchell, 1991;Raftoyannis and Dick, 2002), thus providing a critical tool in the integrated management of the disease. Further experiments are required to confirm field resistance to Phytophthora crown rot in breeding line #181761-36P.…”

Section: Resultsmentioning

confidence: 99%

Inheritance of Resistance to Phytophthora Crown Rot in Cucurbita pepo

Michael¹,

Fu²,

Meru³

2019

horts

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Phytophthora crown rot, caused by Phytophthora capsici Leonian, is a devastating disease in commercial squash (Cucurbita pepo L.) production across the United States. Current management practices rely heavily on the use of chemical fungicides, but existence of fungicide-resistant pathogen populations has rendered many chemicals ineffective. Host resistance is the best strategy for managing this disease; however, no commercial cultivars resistant to the pathogen are currently available. Resistance to Phytophthora crown rot in PI 181761 (C. pepo) is an important genetic resource for squash breeders worldwide; however, the underlying genetic basis of resistance in PI 186761 that would allow designing of sound breeding strategies is currently unknown. The goal of the current study was to determine the inheritance of resistance in breeding line #186761-36P, a resistant selection of PI 181761, using phenotypic data from F1, F2, and backcross populations derived from a cross between #181761-36P and a susceptible acorn-type cultivar, Table Queen. The results indicated that resistance in #181761-36P is controlled by three dominant genes (R4, R5, and R6). Introgression of these genes into susceptible cultivar groups of C. pepo will provide an important tool in the integrated management of Phytophthora crown rot.

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Section: Resultsmentioning

confidence: 99%

Inheritance of Resistance to Phytophthora Crown Rot in Cucurbita pepo

Michael¹,

Fu²,

Meru³

2019

horts

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“…Species-specific temperature requirements have been demonstrated in several studies (Bretzel et al 1988;Hancock 1977;Kuznia and Windels 1993;Raftoyannis and Dick 2002). For example, in a field survey in North Dakota and Minnesota, Kuznia and Windels (1993) found that P. aphanidermatum caused more seed rot and damping-off when soil temperatures increased from 14 to 31°C, whereas the reverse relationship was observed for P. ultimum.…”

Section: Environmentmentioning

confidence: 95%

Management of soilborne diseases of beetroot in Australia: a review

Martin¹

2003

Aust. J. Exp. Agric.

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Soilborne fungal diseases threaten the viability of the Australian processing beetroot industry. Globally, Pythium spp., Aphanomyces cochlioides and Rhizoctonia solani are the predominant soilborne fungal pathogens responsible for a root rot complex in beet crops. In Australia, the disease problems have been exacerbated in recent years because crops are now grown virtually year round, and under environmental conditions favourable to infection. This has lead to increased inoculum levels in soils sown to beetroot. Moreover, nowhere in the world does there seem to be a single strategy that is completely efficacious in controlling these pathogens, so an effective management strategy will almost certainly involve a combination of tactics. The most likely combination seems to involve fungicide seed treatments, rotations of gramineous or biofumigant crops and the use of disease-resistant varieties of beet. The first of these, fungicidal seed dressings, are a cost-effective means of reducing pathogen inoculum and protecting young beets from infection. Hymexazol may be particularly useful in the Australian system, since it is active against both Pythium and Aphanomyces. To combat Rhizoctonia, it should be applied in combination with either pencycuron or toclophos methyl. Second, rotations of gramineous crops, such as maize or oats, or biofumigant brassica crops, such as white mustard, brussel sprouts or cabbage should also reduce the build-up of inoculum and offers a tactic to relieve the problem in the longer term. Third, alternative beetroot cultivars with resistance to Rhizoctonia have now been developed in USA breeding programs and should be considered by the Australian industry. Resistant varieties are potentially very useful since they offer a long-term approach to disease management that can be easily incorporated into existing production systems. Fourth, the alteration of sowing dates to avoid periods of high disease risk (e.g. confining sowing to the cooler, drier months) needs to be seriously considered by the Australian industry if it is committed to disease management. There is also evidence to suggest that seed priming may warrant consideration as a tool to use in combination with fungicide dressings to reduce disease in young plants. Biological seed treatments and soil fumigation appear to be tactics of limited value to the Australian beet industry.

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“…From the literature, and an abundance of anecdotal evidence from greenhouse growers and crop advisory personnel, it is clear that a myriad of variables significantly influence Pythium species and root rot development in hydroponic systems. Important variables range from subtleties such as calcium in the root zone, which at millimolar levels strongly influence adhesion of zoospores to roots (33), to elevated temperature, which can bring about abrupt and explosive increases in root necrosis in large portions of crops (4, 28,39,54,61,83,107). This portion of the present article will now focus on effects of factors associated with the host, the pathogen, the environment of the nutrient solution and plant canopy, and human interferences on disease severity and pathogen ecology.…”

Section: Epidemiology Of Root Rotmentioning

confidence: 99%

Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

et al. 2006

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The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.
A etiologia e a epidemiologia da podridão radicular causada por Pythium spp. em cultivo hidropônico são revisadas com ênfase em conhecimentos e conceitos considerados importantes para o manejo de doenças em estufas comerciais. A podridão radicular causada por Pythium continuamente ameaça a produtividade de diversas culturas em sistemas hidropônicos, incluindo pepino, tomate, pimentão, espinafre, alface, capuchinha, rúcula, rosa, e crisântemo. Os principais agentes causais incluem Pythium aphanidermatum, Pythium dissotocum, espécies de Pythium do grupo F e Pythium ultimum var. ultimum. São apresentadas e discutidas as princip...

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Effects of inoculum density, plant age and temperature on disease severity caused by pythiaceous fungi on several plants

Cited by 31 publications

References 22 publications

Inheritance of Resistance to Phytophthora Crown Rot in Cucurbita pepo

Inheritance of Resistance to Phytophthora Crown Rot in Cucurbita pepo

Management of soilborne diseases of beetroot in Australia: a review

Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

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