Taro leaf blight, a serious disease of taro caused by the fungus phytophthora colocasiae occurs in many countries of south east asia and the pacific trujillo. Phytophthora colocasiae is a water mould, an oomycete, not a fungus. Variations in morphological and molecular characteristics. An epidemic of taro leaf blight in western samoa and american samoa has been confirmed. It also causes pod rot of cacao theobroma cacao and was reported in china on taro colocasia esculenta 12. The possibility of combining the breeding programs is discussed. The disease has become a major constraint for taro production globally.
Mildew taro caused by phytophthora colocasiae affection is the most devastating of taro cultivation in cameroon since 2010. Sridevi2 1department of plant pathology, prof jayashankar telangana state agricultural university, rajendranagar, hyderabad 500 030, telangana, india. Studies on the prevalence of leaf blight disease in taro were conducted in the aowin suaman district of ghana. These sporangia are oval, hyaline, semipapillate tip of spore is not pointed, deciduous spores fall from the colony, and have a short stalk or pedicel attached to the base of the spore. The genus phytophthora includes species causing diseases such as late blight of potatoes, phytophthora infestans, and sudden oak death and ramorum blight, p.
Characterization of isolates of phytophthora colocasiae collected from andhra pradesh and telangana causing leaf blight of taro g. Cytological analysis of defense related mechanisms induced. Evaluation of taro leaf blight disease phytophthora. Isolation and culture of phytophthora take an unripe apple and stab it with needle on one side and press it in to the soil after few days a brown rot appears on the fruit. The effect of certain carbohydrates and amino acids on growth and respiration of phytophthora colocasiae. There is a tendency for these necrotic spots to merge and. It has been studied in leading the influence that can have a parameter considered favourable in the kinetics of the disease, and secondly, the interaction between plots through zoospores that can move from one. Phytophthora colocasiae tlb is caused by phytophthora colocasiae, a hemibiotrophic oomycete plant pathogen raciborski 1900. The oomycete, phytophthora cinnamomi, is a widespread soilborne pathogen that infects woody plants causing root rot and cankering. This book presents an overview of phytophthora diseases. The main objective of this study was to analyze the genetic variation in phytophthora colocasiae populations using ssr markers. Hence, the pathogen was maintained on carrot agar medium to carry out further studies. Taro leaf blight american phytopathological society.
Pectolytic and cellulolytic enzymes produced by phytophthora colocasiae, p. Efficacy of trichoderma harzianum edtm and trichoderma. Pdf mating types of phytophthora colocasiae on the. In the case of regulated organisms, the availability of sensitive and reliable assay is essential. Lesions are the result of oomycetes leaching nutrients out of the leaves via haustoria to create white powdery rings of sporangia. It needs moist soil conditions and warm temperatures to thrive, and is particularly damaging to susceptible plants e. Phytophthora leaf blight of taro colocasia esculenta a. Both a1 and a2 mating types have been reported and it is believed that the fungus. Identifying species by morphology and dna fingerprints, enables diagnosticians and regulatory personnel as well as researchers to identify phytophthora species with speed and confidence. Wingfielda adepartment of microbiology and plant pathology, forestry and agricultural biotechnology institute fabi, university of pretoria, pretoria 0002, south africa bschool of biological sciences and biotechnology, murdoch university, murdoch 6150.
Two previously unknown phytophthora species associated with. Origin and distribution of four species of phytophthora. The word phytophthora is derived from the greek language that is literally translated into plant destroyer. Please participate on that page and not in this talk. Seven primer pairs produced 431 markers, of which 428 99.
The most significant plant disease affecting taro is taro leaf blight tlb, caused by phytophthora colocasiae. Full length research article leaf blight disease caused by phytophthora colocasiae is the main constraint affecting taro plants in tropical and subsubtropical countries. Phytophthora colocasiae is one of the most destructive diseases of taro colocasia esculenta, causing leaf blight and corm rot of taro. Habitat of phytophthora symptoms of phytophthora vegetative structure of phytophthora reproduction in phytophthora some common. There were only about 50 identified species when the last key was published in 1990, but now that species. The presence of yellow tissue around lesions figure 8 is not well understood, but could be a cultivarspecific reaction or a stress response to dry weather. The failure to adequately identify plant pathogens from culturebased morphological techniques has led to the development of cultureindependent molecular approaches. Taro cultivation in the solomon islands is in decline because of severe disease and insect problems. Two new phytophthora species from south african eucalyptus plantations bongani masekoa, treena i. Taro leaf blight caused by phytophthora colocasiae is the most destructive disease of taro.
The oomycetous fungus phytophthora colocasiae causing leaf blight of taro is widely distributed in india. Characterization of isolates of phytophthora colocasiae. Field trials were conducted to determine the effect of fungicides and the spray regimes on leaf growth, disease incidence, disease severity and tuber yield of cocoyam. Characterizing the pathogenicity profiles of phytophthora. Modelling of infection mildew of taro phytophthora colocasiae.
It was first reported from java in 1900 raciborski 1900. A taro breeding program was established at the university of hawaii to develop taro varieties with improved characteristics including resistance to tlb. Bright orange or reddish brown plant exudate oozing from infection sites is another symptom of leaf blight disease in taro figure 7. The vanuatu breeding program is based on combining genotypes. Schott is an important tropical tuber crop, used as a staple food or subsistence food by millions of people in the developing countries in asia, africa, and central america. A synopsis of phytophthora with accurate scientific names. Colocasiae esculenta var antiquorum l schott and colocasiae esculenta var. Isozyme and pcrbased genotyping of epidemic phytophthora. Morphological and molecular techniques were used to characterise the population of phytophthora colocasiae obtained from different locations in ghana. Disease incidence was assessed on two taro accessions namely. Studies on morphological characters of different isolates of phytophthora colocasiae revealed that the mycelium of phytophthora colocasiae was aseptate, hyaline with hyphal width of 1. To control the disease, farmers commonly use chemical pesticides. We do not use these to store personal information about you.
Uppal research 2fellow, iowa agricultural experiment station introduction in recent years a large amount of work has been done on spore germination in relation to. Disease and pest problems of taro colocasia esculenta l. Pdf taro leaf blight tlb caused by phytophthora colocasiae is a damaging disease that destroyed samoas taro industry following its. Agriculture 2012, 2 184 yield by up to 50% 710 and leaf yield by 95% in susceptible varieties 11. Taro leaf blight phytophthora colocasiae is a highly infectious plant disease that is characterized by the formation of large brown lesions on the leaves of infected taro plants. Rapid and sensitive detection of phytophthora colocasiae. Modelling of infection mildew of taro phytophthora. Pdf first report of taro colocasia esculenta leaf blight.
It has been studied in leading the influence that can have a parameter considered favourable in the kinetics of the disease, and secondly, the interaction between plots through zoospores that can move from one field to another while estimating their dispersal throughout. The development of sustainable and appropriate management strategy to control leaf blight of taro depends on a good understanding of the population structure of its causal pathogen. Plantdisease72n10 909 american phytopathological society. Genetic diversity of phytophthora colocasiae isolates in. Mildew taro caused by phytophthora colocasiae affection is the most devastating. The spots merge and secondary spots develop photo 6, and rapidly a blight develops as most of the leaf blade. Phytophthora colocasiae that causes taro leaf blight is one of the most devastating diseases of taro which is widely distributed in india. Breeding strategies for controlling diseases of taro in solomon.
United states department of new pest response agriculture. In this article we will discuss about phytophthora. Cytological analysis of defense related mechanisms induced in taro 199 fig. Infected corm tissue is brown, firm, and develops rapidly after harvest. Pdf mating types of phytophthora colocasiae on the island of. Analysis of genetic diversity in phytophthora colocasiae. Phytophthora colocasiae produces microscopic, asexual spores called sporangia. Laboratory experiment was conducted to test the possibility of combining trichoderma. Pdf in november 2009, many farmers in abia state were alarmed by complete. Field management of phytophthora blight disease of cocoyam.
Phytophthora infestans is a wellknown species of phytophthora, which causes late blight potato blight. The studies comprised a survey to assess the incidence and severity of the taro leaf blight disease in ten communities in the district in. Phytophthora colocasiae, taro leaf blight, trichoderma, biochemical defense. Besides, the pathogen also causes the serious postharvest decay of corms.
Phytophthora colocasiae on taro and phytophthora recovered from streams in eastern tennessee. Information is presented on possible origins, and on the distribution of four species of phytophthora. Because of the importance of diseases caused by phytophthora, there is a need to have rapid access to the literature using their scientific names. Leaf blight has become a limiting factor in all tarogrowing countries, including india, causing yield loss of up to 50% gollifer and. A brown firm rot in the top part of a corm caused by the water mould, phytophthora. Note the concentric rings, lesions merge as they develop, causing extensive necrosis of the leaf. United states department of agriculture marketing and regulatory programs animal and plant health inspection service plant protection and quarantine cooperating state departments of agriculture july 09, 2010 new pest response guidelines phytophthora species in the environment and nursery settings. Leaf blight caused by phytophthora colocasiae raciborski is the most destructive disease of taro. General information about phytophthora colocasiae phytoo this website uses cookies our website uses cookies to ensure that we give you the best possible online experience. This knowledge can be further exploited for the development of a good breeding strategy and utilization of plant resistance mechanisms for the effective disease management. Taking into account the needs of graduate students, scientists, and agricultural professionals, this volume integrates guides to literature, background information, physiology and genetics, the effect of environmental factors on disease, control by biological and cultural means, resistant cultivars, fungicides, and techniques for.
Fungal diseases, the most important of which is leaf blight caused by phytophthora colocasiae rac, result in considerable crop losses. The timely and accurate detection of pathogens is a critical aid in the study of epidemiology and biology of plant diseases. Place a portion of the rotted tissue in a dish containing tap water. I think the species of phytophthora mentioned may be phytophthora colocasiae rac. Ooka department of plant pathology university of hawaii kauai branch station abstract although taro is susceptible to attack by at least twentythreepathogens, only a few cause serious reduction in growth and production.