CP 102 Principles of Plant Disease Diagnosis & Management 2024-2025 PDF

02/10/2024 CP 102 Learning objectives Principles of Plant At the end of the chapter, the student must be able to: Disease Diagnosis...

02/10/2024 CP 102 Learning objectives Principles of Plant At the end of the chapter, the student must be able to: Disease Diagnosis 1. Know the characteristics of plant parasitic nematodes. and Management 2. Understand the importance of plant parasitic nematodes. 1st Semester 2024-2025 3. Know the different techniques in diagnosing nematodes. 4. Identify and characterize plant parasitic nematodes. Joanne A. Langres, MSc Assistant Professor IV 2 1 2 Definition of Terms What are the Nematology characteristics of ▪ is the scientific discipline conventionally concerned with the study of phyto-nematodes which parasitize plants and are of phytopathogenic economic importance to agriculture, horticulture and nematode? "Nematode" is a greek word (nema = thread, oides = form) i.e. thread like organisms as they look like tiny threads moving under microscope. 3 3 4 ▪ Nematodes possess a false body cavity General Characteristics or pseudocoelom i.e. a cavity lacking mesodermal lining internally or a cavity present between mesoderm and ▪ Belongs to Phylum Nematoda endoderm. Pseudocoelom is fluid filled ▪ bilaterally symmetrical and most part of it is occupied with intestine and components of ▪ The body is covered by a transparent, tough, resistant cuticle that reproductive system is secreted by a layer of hypodermal (epidermal) cells lying just beneath it. ▪ Oral aperture (mouth) is terminal and is surrounded by lips which contain ▪ protrusible hypo-pharyngeal needle like knobbed stylet (spear) at sensory cephalic papillae. the anterior end of the body, which is used to suck the cell cytoplasm from the host plants. ▪ All other body openings like excretory pore, vulva and anus (in females) and ▪ Fungal feeding nematodes also possess stylet which may or may cloacal aperture (in males)are ventrally not be knobbed 5 located (Fig. 3.2) 6 5 6 1  02/10/2024 ▪ Plant parasitic nematodes are small worm-like Plant parasitic animals that have a cuticle made of chitin and a piercing mouthpart called a stylet Nematodes (PPN) ▪ free-living species, which are more common in soil samples, do not have stylets ▪ Plant parasitic nematodes are small worm-like ▪ Shape: animals that have a cuticle made of chitin and a ✓ elongated piercing mouthpart called a stylet ✓ kidney-shaped ▪ free-living species, which are more common in soil ✓ globose samples, do not have stylets ▪ PPN are mostly obligate parasite 7 8 7 8 Plant Parasitic Nematode Nematode Morphology 10 9 10 Morphology Morphology … the cross section of a nematode body looks like a “tube within a ▪ Inner Tube tube” begins from the mouth opening to the anus (for female) or cloaca (the Outer Tube common opening of digestive and reproductive systems for male) Cuticle – semi-permeable outermost covering of the nematode body; possess stylet that they use in puncturing plant cells and withdrawing made up of protein (keratin and collagen); shed off during molting to their contents allow growth Epidermis – thin layer which functions mainly for secretion of new cuticle during molting Muscles – allows movement by alternate contraction and relaxation of dorsal and ventral muscles 11 12 11 12 2  02/10/2024 Types of Stylet ▪ The life cycle of a plant parasitic nematodes has six stages: egg, four juvenile stages and a. Stomatostylet – with distinct cone, shaft and adult knobs; inside hallow; possessed by members of the ▪ It undergoes molting in between stages. Order Tylenchida ▪ Most species produce between 50 b. Odontostylet – a hallow spear; possessed by and 500 eggs per female depending on the nematode species and their members of the Order Dorylaimida environment. c. Onchiostylet – a bent solid needle-like stylet ▪ Some species produce more than 1,000 eggs possessed by members of the Order Triplonchida ▪ All motile nematode stages 13 are capable of feeding from the plant. eggs - larva (four molts) - adult 14 13 14 Reproduction Means of Amphimictic – nematode species which requires the presence of both female and male for reproduction to occur. Dissemination Parthenogenic – nematodes reproduce from eggs without fertilization by sperm ✓ Water cells. ✓ Soil Hermaphroditic – possessing both functional male and female reproductive organs. ✓ plant materials Sexual dimorphism – phenomenon wherein the male and female nematodes of ✓ insects the same species have entirely different morphology. ✓ contaminated equipment Sex reversal – phenomenon observed in juveniles of parthenogenic species of Meloidogyne during unfavorable condition. Depending on the onset of the unfavorable condition, the gonad of “destined to be” female juveniles develops into non-functional testis. 15 16 15 16 ▪ Although most nematodes are parasitic on roots, Signs and Symptoms of some nematodes are parasitic on aerial portions of plants (e.g. Aphelenchoides fragariae) nematode infection Foliar Nematode Typical root symptoms indicating nematode attack are root knots or galls, root lesions, excessive root branching, injured root tips and stunted root systems 17 18 17 18 3  02/10/2024 ▪ Symptoms on the above-ground plant parts indicating root infection are a slow decline of the entire plant, wilting even with ample soil moisture, foliage yellowing and fewer and smaller leaves. These are, in fact, the symptoms that would appear in plants deprived of a properly functioning root system. ▪ Bulb and stem nematodes produce stem swellings and shortened internodes ▪ Bulb and stem nematodes produce stem swellings and shortened internodes 20 19 20 4