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1. MASTER SEMINAR ON HYPERPLASTIC SYMPTOMS INDUCTION BY PLANT PATHOGENS SESSION- 2023-24 INDIRA GANDHI KRISHI VISHWAVIDYALAYA COLLEGE OF AGRICULTURE, IGKV, RAIPUR (C.G) DEPARTMENT OF PLANT PATHOLOGY PRESENTED BY Bhuneshwari Sahu College Id- 20230125 M.Sc. (Ag) 1 st Year 2 nd Semester

2. Introduction Some important diseases representing various abnormal growth Described Diseases- Crown gall diseases Club root of Crucifers Stem & Bulb nematode of Onion Conclusions Reference Content

3. Hyperplastic Symptoms Symptoms associated with hyperplasia include club root, galls, wart, and leaf curls. In some instances, the fungus infecting the plant may produce growth or structures on the plant, stems, or leaves such as masses of mycelium or aggregates of spores with a characteristic appearance. Hyperplasia:- A plant overgrowth due to increased cell division. Sometimes the plant part become abnormal in size due to increase in size of cell called hyperplasia. The abnormal growth is due to disturbances in the hormonal control of growth & differentiation. Hyperplasia is excessive cell division causing plant overgrowth resulting in growth such as galls, tumors, enation (an outgrowth from a leaf or stem often associated with viral infection) proliferation, and witches-broom. Introduction

4. Some important diseases representing various Abnormal growth are- Bacterial diseases 1. Crown gall disease - Agrobacterium tumef aciens 2. Leafy gall of Sweet Pea- Rhodococcus fascians Fungal diseases 1 . Club root of Crucifers- Plasmodiophora brassicae (Finger & Toe Disease) 2. Wart disease of Potato - Synchytrium endobioticum 3. Peach leaf curl- Taphrina deformans 4. Corn smut- Ustilago maydis 5. Gall rust of Pine - Endocronartium harknessii 6. Cedar apple rust- Gymnosporangium juniperi-virginiane Nematodal diseases 1 . Root knot disease- Meloidogne spp . 2. Stem and bulb nematode- Ditylenchus spp.

5. Crown gall is found all over the world. It has been studied extensively because of its superficial resemblance to human and animal cancers. Crown gall has served as a model system to understand the tumorization process at molecular level. The bacterium is called " Nature's genetic engineer ". 'What scientists are doing now; the crown gall bacterium has been doing since ages. It has been used in plant genetic engineering as a 'vector ' for introducing the 'foreign ' gene. Only 1% of the isolates is pathogenic & these contain the Ti-Plasmid, which is essential for pathogenesis & tumerization . They include especially grape, members of the rose family ( Rosaceae ), shade and nut trees, many shrubs and vines, and perennial garden plants. Crown Gall Disease ( Agrobacterium tumef aciens )

6. Crown gall first appears as small, round, whitish, soft overgrowths on the stem and roots, particularly near the soil line. As the tumors enlarge, their surfaces become convoluted, and the outer tissues become dark brown due to the death and decay of the peripheral cells. Others become woody and hard, looking knobby or knotty, and reaching sizes up to 30 centimeters in diameter. Some tumors rot in the fall and develop again during the next growing season. Several galls may occur on the same root or stem, continuous or in bunches. Tumors, however, can also appear on vines up to 150 centimeters from the ground, on branches of trees, on petioles, and on leaf veins. Symptoms

7. The Pathogen : Agrobacterium tumefaciens A soil borne Gram negative bacterium. This bacterium is rod shaped with a few peritrichous flagella. Virulent bacteria carry one to several large plasmids (small chromosome like bodies composed of circular double-stranded DNA). One of these plasmids carries the genes for tumor induction and is called the tumor-inducing plasmid ( Ti-plasmid). The most characteristic property of this bacterium is its ability to introduce part of the Ti plasmid (T-DNA) into plant cells and to transform normal plant cells to tumor cells in short periods of time.

8. Ti-plasmid Ti-plasmid, is an extra-chromosomal molecule of DNA found commonly in the plant pathogen Agrobacterium tumefaciens . A Ti-plasmid is a circular piece of DNA found in almost all Agrobacteria . It carries numerous genes involved in the infection process:- Virulence Region: The virulence region codes for virulence genes that are responsible for the transfer of T-DNA to the plant cells. T-DNA Region: The T-DNA region is the crucial region that gets transferred to the plant cell for infection. Opine Catabolism Region : The opine catabolism region is the region from where the bacteria sources its nutrients for the whole process. Origin of Replication: The origin of replication is the region where replication of the plasmid is initiated.

9. Mechanism of T-DNA Transfer- Agrobacterium tumefaciens is a soil phytopathogen that naturally infects plant wound sites and causes crown gall disease via delivery of transferred (T)-DNA from bacterial cells into host plant cells through a bacterial type IV secretion system (T4SS).

10. Step 5: Transfer of T-DNA from Bacteria to Plant Cell & Step 6: Integration of T-DNA into Plant Genome

11. Fig.- Disease Cycle of Crown gall caused by Agrobacterium tumefaciens Development of Disease

12. Management Use of certified, disease-free planting materials. Measures that prevent wounding. Use of resistant cultivars. Resistant varieties of Rose is Rosa picogol  showed resistance to crown gall disease by blocking the attachment of bacteria to the wound surface with exudates. Soil sterilization by steam (at 82°C for 30 minutes) or soil fumigation with methyl bromide, chloropicrin. Removal and destruction of diseased plants, and change over to other crop for 5 years. Excellent biological control of crown gall is obtained by soaking germinated seeds or dipping nursery seedlings or rootstocks in a suspension of a particular strain (No. 84) of Agrobacterium radiobacter . This strain of bacteria is antagonistic to most strains of A.tumefaciens .

13. Club Root of Cabbage or Finger & Toe Disease ( Plasmodiophora brassicae ) Infected plants at first have pale green to yellowish leaves. Later, infected plants show wilting in the middle of hot, sunny days, recovering during the night. Wilting symptoms Club Root symptoms Symptoms The most characteristic symptoms of the disease appear on the roots as spindle-like, spherical, knobby, or club-shaped swellings. The swellings may be few and isolated or they may coalesce and cover the entire root system. The older and usually the larger clubbed roots disintegrate before the end of the season because of invasion by bacteria and other fungi.

14. Pathogen : Its body is a Plasmodium (Naked slimy mass of protoplasm containing numerous nuclei) gives zoosporangia/resting spores released into soil when decayed and produce zoospores. Zoospores are biflagellate, unequal in length and uninucleate , both the flagella are of whiplash type. Resting spores are tiny, hyaline spherical, haploid, uninucleate with spiny walls. Resting spore Plasmodium

15. Mechanism The disease cycle of club root of crucifers begins as haploid resting spores in the soil germinate to form primary zoospores. These spores, as agents of dispersal, identify, encyst , and penetrate the root hairs of susceptible hosts. A primary, multinucleate plasmodium forms as the nuclei divide through mitosis.

16. Disease cycle of Club root of Crucifers

17. Management Choose well-drained sites, free of the club root pathogen for crop production. Rotations, which include cereals and other non-host crops for 7 or more years, have been helpful at minimizing the incidence of club root in some areas. Amendment of soil to adjust pH to 6.8 using ground limestone (CaCO3), hydrated lime (Ca(OH)2) or combination of hydrated lime and PCNB i.e. penta - chloro -nitrobenzene. Seedlings can carry the pathogen so the use of disease free seedlings is therefore very important. Seed treatment with Captan or Thiram 4g/Kg, followed by T. viride 4g/Kg. Soil drenching with Copper oxychloride 0.25%.

18. Nematodes are triploblastic , bilaterally symmetrical, unsegmented , vermiform and colourless . Ditylenchus dipsaci is a plant pathogenic nematode that primarily infects onion and garlic. It was first recorded in Netherlands in 1883 . It attacks a large number of host plants, including Alfalfa, Onion, Garlic, Hyacinth, Tulip, Oat, and Strawberry . Stem and bulb nematode of Onion ( Ditylenchus dipsaci ) The stem and bulb nematode is an endoparasitic migratory nematode. (Migratory endoparasites can move into, through, and out from host tissues at any stage of development (except the egg). Migratory endoparasites generally live and feed in tender tissues such as the root cortex).

19. Symptoms- When infection occurs in seedlings, they become dwarfed, twisted and abnormally white and also develop swollen areas where the epidermis sometimes splits. Young plants show stunting, light yellow spots, swellings on the stem, shorter and curled leaves, and swollen base. Older infected bulbs show swelling (bloat) of scales. Onion have a frosted appearance caused by the dissolution of cells that results from nematode feeding. As the season advances the bulbs become soft and when cut open show browning of the scales in concentric circles and give off a foul odor.

20. Mechanism Inside the infected plant tissue, the nematodes hatch from an egg as a second stage juvenile and continue to feed and molt into a third stage and later a fourth stage juvenile. It is the fourth stage larval phase that will exit plant tissue in search of a new host .

21. Disease cycle Fig- Disease cycle of Stem & Bulb Nematode

22. Management The use of nematode-free sets or seeds is extremely important. Infested seeds or bulbs can be disinfested by treating them with hot water for 1 hour at 46°C, with a nematicide in a gas-tight container, or with 0.5% formaldehyde. In the field, control can be achieved by fall fumigation of the soil, by preplant row treatment, and by treatment at or soon after planting with appropriate nematicides . Nematophagous fungi such as Verticillium balanoides may be suitable for development as biological control agents for D. dipsaci . Metam Sodium, Dazomet , and Methyl Isothiocyanate (MITC) nematicides most commonly used for nematodes control. Metam sodium is a soil fumigant used to control nematodes.

23. Conclusions Plasmodiophora brassicae is a highly persistent pathogen capable of infecting a multitude of agricultural important crops, break crops, common weeds and enduring more than 17 years in the soil. Plant pathogens induces phytohormone manipulation of the host carbon metabolism and physiological processes by predominantly auxins and cytokinins , leading to excessive cell development (hypertrophy and hyperplasia). Agrobacterium tumefaciens induced tumor formation in plant by transformation. and stimulate to production of novel plant hormone- opine. Plant pathogens secreted enzymes in host cell, that catalyze the formation of cell hormones, responsible for cell elongation and cell division resulting gall formed. Poor cell differentiation in root galls leads to decreased uptake of water and nutrients for the plant, eventually leading to plant death .

24. Reference: Aagrios G.N., (2005). Plant Pthology , Page no. 407-409, 662-666, 858-861. Comelis , K. et al., (2001). The plant pathogen Rhodococcus fascians colonizes the exterior and interior of the aerial parts of the plants. MPMI 14 (5) pp 599-608, American Phytopathological Society. Dube H.C., (2020). Modern Plant Pathology, Page no. 435-455. Laidlaw, W.M.R. (1985). A method for the detection of the resting sporangia of potato wart disease ( Synchytrium endobioticum ) in the soil of old outbreak sites. Potato Research 28: 223-232. Vyas , R.V. and Patel, D.J. (2000). Biological control of root-knot nematodes in India. In: Annu . Rev. Plant Pathology. (Ed. Dube HC et al.). Indian Soc. Mycol Plant pathol . India.