Subdivision: Zygomycotina (Mucorales) General characters of Zygomycotina Majority of them are saprobic some are coprophilous some are weak parasites attacking plants. It produces well-developed, branched coenocytic mycelium. Cell wall is composed of chitin –chitosan. Asexual spores are non-motile and are called sporangiospores. Sexual spores are zygospores. Key to the classes of Zygomycotina Class: Zygomycetes Saprobic […]

Viroids Viroids area covalently closed circular RNA molecules. Viroids were the first circular RNAs to be discovered in nature. These are the smallest known infectious agents. Potato spindle tuber viroid was the first viroid reported, and it is widely prevalent in different potato growing areas. Citrus exocortis viroid is wide spread in citrus production areas […]

Systemic Fungicides and Antibiotics Systemic Fungicides Since the late 1960s there has been substantial development in systemic fungicides. Any compound capable of being freely translocated after penetrating the plant is called systemic. A systemic fungicide is defined as fungitoxic compound that controls a fungal pathogen remote from the point of application, and that can be […]

Terms and Concepts in Plant Pathology Plant diseases in the landscape and garden are very important and can be a significant source of frustration and loss to the gardener. There are about 30,000 diseases of economic importance. Plant pathology is the study of the biotic and abiotic agents that cause disease in plants; of the […]

Survival of Plant Pathogen Any pathogen can cause disease under favorable conditions. The only requisite factor is that the pathogen must come in contact with the host for the development of the disease. Pathogen itself or its parts that are capable of causing disease when brought near a host is called inoculum. Fungal pathogens are […]

Symptoms of leaf spots, leaf blights, root rots and wilts and disease cycles Leaf Spot In leaf spot a well marked necrotic area of grey, brown, purple or black tissues in green leaves. i. Blast of rice – Pyricularia oryzae Systematic position Sub-kingdom : Mycota Division : Eumycota Sub-division : Deuteromycotina Class : Hyphomycetes Order […]

Sexual Reproduction Sexual reproduction in fungi involves union of two compatible nuclei. The nuclei may be carried in motile or non-motile gametes, in gametangia or in somatic cells of the thallus. Phases of sexual reproduction Three typical phases occur in sequence during the sexual reproduction. 1. Plasmogamy In plasmogamy (Gr. plasma=a molded object, i.e. a […]

Reproductive structures Fungi reproduce by means of their propagules. In most fungi the propagules are differentiated as spores. But in some fungi the stromatic aggregations of hyphae like the sclerotia also perform the function of propagation. The simple or branched spore-bearing hyphae are known as sporophores, but in some fungi the spores may be formed […]

Plant viruses Virus is a submicroscopic, transmissible, intercellular, obligate parasite and consists of nucleic acid (either RNA or DNA), which is typically surrounded by a protein coat. They are less than 200 millimicron and cannot be grown in artificial media and require living host cell for multiplication. They have both living and nonliving properties. Living […]

Prokaryotes Phytoplasma Phytoplasmas are small, unicellular, gram-positive non-motile bacteria like prokaryotes intermediate between viruses and bacteria. They differ from true bacteria in the absence of cell wall. Phytoplasma is first observed in the phloem of the mulberry plants infected with dwarf disease. Highly pleomorphic and their size range from small spherical bodies to large irregularly […]