Plant pathology

An introduction, disease cycle, different types of diseases, causal agents, control measures

1. PLANT PATHOLOGY: AN INTRODUCTION PRESENTED BY: BHUMIKA ARORA DEPARTMENT OF BOTANY AKAL UNIVERSITY MSC 3 rd SEM UID NO.= 180607004

2. CONTENTS INTRODUCTION TERMS OBJECTIVES IMPORTANT EVENTS IN PLANT PATHOLOGY LOSES CAUSED BY DIFFERENT PEST IN CROPS PLANT DISEASES PLANT PATHOGENS DISEASE CYCLE TYPES OF DISEASES AND THEIR CAUSAL AGENTS CONCLUSION REFERENCES

3. INTRODUCTION FATHER OF PLANT PATHOLOGY IS “ HEINRICH ANTON DE BARY “ → IT IS ALSO CALLED AS PHYTOPATHOLOGY . PHYTON (PLANT) PATHOS (SUFFERING) LOGOS (STUDY) → PLANT PATHOLOGY IS THE BRANCH OF AGRICULTURE , BOTANICAL OR BIOLOGICAL SCIENCE WHICH DEALS WITH THE STUDY OF THE CAUSES , RESULTING LOSSES AND MANAGEMENT / CONTROL OF PLANT DISEASES .

4. TERMS HOST : An organism that supports the activities of a parasite is known as host. INOCULUM : It is the infectious material that can cause disease, and is that portion of pathogens that comes in contact with the host. FUNGITOXIC : These are the substances which are harmful to the fungi and these include fungicides. FUNGICIDE : These are the chemicals which are capable of killing fungi ACERVULUS : A subepidermal , saucer- shaped , asexual fruiting body producing conidia on short conidiophores.

5. TERMS ASCUS : A sac-like cell of a hypha in which meiosis occurs and that contain ascospores. AVIRULENCE : The inability of a pathogen to infect a certain plant variety . PUSTULE : Small blister-like elevation of epidermis created as spores from underneath and push outward. SMUT : These are the fungal diseases which cause the ears to turn black. It also cause other parts of the plant. RUST : These are the fungal diseases that appear on the host surface as small, coloured pustules – red , brown, orange, black in colour

6. TERMS WHITE BLISTERS : These are white, shining ,blister like pustules found on the leaves of cruciferous plant . These pustules visible as powdery masses of spores. BLIGHT : In many plants leaves, stems in response to the attack of pathogen undergo rapid discolouration and leads to death. ROT : It is a disease in which the affected tissues die and undergo decay .It may effect leaves, roots , stem , buds of the host plant. WARTS : These are the outgrowths that develop on tubers and stems showing discoloured cauliflower like appearance . MILDEW : These are the fungal diseases of plants in which pathogen has superficial on host surface (leaves , stems) in the form of patches of varying sizes and colours.

7. OBJECTIVES OF PLANT PATHOLOGY 1) TO STUDY THE BIOTIC , ABIOTIC CAUSES OF PLANT DISEASES. 2) TO STUDY THE MECHANISM OF DISEASE DEVELOPMENT. 3) TO STUDY THE INTERACTION BETWEEN PLANT AND PATHOGEN. 4) TO DEVELOP THE METHODS OF PLANT DISEASE MANAGEMENT/CONTROL.

8. IMPORTANT EVENTS IN PLANT PATHOLOGY 1845-46 LATE BLIGHT OF POTATO / IRISH FAMINE. 1867 COFFEE RUST IN SRI LANKA 1869 COFFEE RUST IN SOUTHERN INDIA 1918-19 BROWN LEAF SPOT OF RICE IN DELTA OF KRISHNA AND GODAWARI RIVERS 1943 BROWN LEAF SPOT OF RICE/BENGAL FAMINE 1956-57 RUSTS IN BIHAR

9. LOSES CAUSED BY DIFFERENT PEST IN CROPS PEST LOSS(%) WEED 33 DISEASES 26 INSECTS 20 STORAGE PESTS 7 RODENTS 6 OTHERS 8 TOTAL 100

10. PLANT DISEASES A DISEASE IS A PARTICULAR ABNORMAL CONDITION THAT NEGATIVELY AFFECTS THE STRUCTURE OR FUNCTION OF PART OR ALL OF AN ORGANISM.

11. TYPES OF PLANT DISEASES INFECTIOUS OR BIOTIC ,PLANT DISEASES DISEASES CAUSED BY FUNGI DISEASES CAUSED BY PARASITIC HIGHER PLANTS DISEASES CAUSED BY VIRUSES DISEASES CAUSED BY NEMATODES DISEASES CAUSED BY BACTERIA NON-INFECTIOUS ,OR ABIOTIC PLANT DISEASES DISEASES CAUSED BY TEMPERATURE DISEASES CAUSED BY SOIL MOISTURE DISEASES CAUSED BY POLLUTION DISEASES CAUSED BY LIGHT

12. TYPES OF PLANT DISEASES

13. INFECTIOUS DISEASES A) ENDEMIC DISEASES : A disease which is present from year to year in a certain region ( country) or a part of a region (district ) is a referred to as endemic. The environmental conditions are favourable for its development. The causal agent is well established in the locality. B) EPIDEMIC DISEASES : Diseases which spread widely but occur periodically. The causal agent may be regularly present in the locality but the environmental conditions are favourable but occur periodically. C) SPORADIC DISEASES : These are the plant diseases which occur at irregular intervals or occasionally .

14. PLANT PATHOGENS Any agent which is capable of causing disease in the plants. Most microbes attack only a specific part of the plant and produce disease symptoms , such as a spotting , wilting , powdery mildew etc. The term pathogen is restricted to living agents , which include: Viruses( living proteins),Bacteria ,Fungi and some insect larval stages.

15. ▪ THE PLANT DISEASES ARE CAUSED BY FOLLOWING PATHOGENS: 1 ) PARASITIC FUNGI : They produce a great majority of the parasitic plant diseases called fungal diseases. These diseases cause damage and destruction . Ex : Albugo candida cause white rust of crucifers 2) PARASITIC BACTERIA : They also cause many plant diseases . Ex : Xanthomonas sp. cause citrus canker 3) PARASITIC SEED PLANTS : There are few phanerogamic parasites which cause plant diseases. Ex: Dodders (Cuscuta) etc. Cntd…...

16. 4) PARASITIC ALGAE : There are very few parasitic algae that cause plant diseases. Ex : Cephaleuros parasitica cause orange rust of tea 5) VIRUSES : These are the pathogens which almost completely dependent upon their host for their growth and replication. They cause serious plant and animal diseases. Ex : Yellow vein mosaic virus in bhindi

17. TYPES OF PLANT PATHOGENS

18. DISEASE CYCLE The chain of events that leads to the development of a disease is called disease cycle . ELEMENTS OF THE DISEASE CYCLE : Host Pathogen Environment

19. TYPICAL DISEASE CYCLE

20. PLANT DISEASES AND THEIR CAUSAL ORGANISMS

21. S.NO. DISEASES PATHOGENS 1) WART DISEASE OF POTATO Synchytrium endobioticum 2) LATE BLIGHT OF POTATO Phytophthora infestans 3) WHITE RUST OF CRUCIFERS Albugo candida 4) DOWNY MILDEW OF BAJRA Sclerospora graminicola 5) POWDERY MILDEW OF GRAPEVINE Uncinula necator 6) BROWN RUST OF WHEAT Puccinia triticina 7) BLACK RUST OF WHEAT Puccinia graminis tritici 8) YELLOW RUST OF WHEAT Puccinia striiformis

22. S.NO. DISEASES PATHOGENS 9) LOOSE SMUT OF WHEAT Ustilago tritici 10) RED ROT OF SUGARCANE Colletotrichum falcatum 11) TIKKA DISEASE OF GROUNDNUT Cercospora sp. 12) ROOT KNOT OF VEGETABLE CROPS Root – knot nematodes 13) EAR COCKLE OF WHEAT Anguina tritici 14) KARNAL BUNT OF WHEAT Tilletia indica 15) YELLOW VEIN MOSAIC OF BHINDI Monopartite begomovirus 16) LITTLE LEAF OF BRINJAL Phytoplasma

23. WART DISEASE OF POTATO host Solanum tuberosum PATHOGEN Synchytrium endobioticum SYMPTOMS The disease occur on the underground parts except roots i.e. tubers , buds , stems, and stolons. There is a Cauliflower like outgrowths on infected parts. In the early growing season they are greenish white in colour. In advanced stages, the warts become dark black in colour.

24. WART DISEASE OF POTATO Resting spore

25. WART DISEASE OF POTATO DISEASE CYCLE CONTROL MEASURES The diseased potato area should be discarded. Soil treatment may control the disease to a large extent .This include steam sterilization, mercuric chloride and copper sulphate application and formalin. It is very costly. Cultivation of disease resistant varieties continuously for 8-10 years.

26. LATE BLIGHT OF POTATO HOST Solanum tuberosum PATHOGEN Phytophthora infestans SYMPTOMS The disease appears on the top of the plant i.e. on the tip and margins of the leaflets , petiole , stem and this is mainly infected in the field. The disease makes its appearance as dead ,small , brownish to purplish black areas. There is more discoloration of the skin of those parts of the tubers which lie nearest to the surface of the soil.

27. LATE BLIGHT OF POTATO Lemon shaped sporangia

28. LATE BLIGHT OF POTATO DISEASE CYCLE CONTROL MEASURES The seed tubers should be free from the disease. Storage of potato tubers in cold storage. By spraying fungicides such as Blitox-50 etc. in proper time. The tubers should be dipped in mercuric chloride solution for 90 minutes before storage.

29. WHITE RUST OF CRUCIFERS HOST Members of Crucifers like Brassica sp. , Raphnu s sativus , etc. Pathogen Albugo candida SYMPTOMS The disease affects all the aerial parts of the plant, roots are not affected. There are 2 types of infection : Local and Systematic . In local infection, spots appear on leaves, stems . These spots have variable size. In systematic infection, young stems and inflorescence are infected.

30. WHITE RUST OF CRUCIFERS Conidia

31. WHITE RUST OF CRUCIFERS DISEASE CYCLE CONTROL MEASURES Cultivation practices should be followed and destruction of weed should be done. Crop rotation prevent the disease. Disease resistant varieties should be preferred.

32. DOWNY MILDEW OF BAJRA HOST Pennisetum glaucum PATHOGEN Sclerospora graminicola SYMPTOMS In this there are two stages of symptoms. One is downy mildew stage, in which leaf is affected and leaves then start showing chlorotic streaks on their upper surface and just opposite to streaks on lower surface. Other is the green ear stage, affecting inflorescence. In this a whole or a part of inflorescence is transformed into twisted leafy structure.

33. DOWNY MILDEW OF BAJRA Sporangia of Sclerospora SEM Inflorescence of Bajra Diseased spikelet

34. DOWNY MILDEW OF BAJRA DISEASE CYCLE CONTROL MEASURES Removal of the infected tissues Crop rotation Deep ploughing Use fungicides Some of the resistant cultivars like NHB 10 etc. are resistant to downy mildew.

35. POWDERY MILDEW OF GRAPEVINE HOST Vitis vinifera PATHOGEN Uncinula necator SYMPTOMS The disease attacks the vines at any stage of their growth All aerial parts of the plant are attacked Floral infection results in shedding of flowers Powdery growth is visible on berries and the infection results in the cracking of skin of the berries.

36. POWDERY MILDEW OF GRAPEVINE Lower Surface of Leaf On fruit surface

37. POWDERY MILDEW OF GRAPEVINE DISEASE CYCLE CONTROL MEASURES Resistant varieties should be grown Fungicides like Sulphur etc. should be used to control the disease The use of fungicides for control of powdery mildew should begin during early stages of vine development

38. BROWN RUST OF WHEAT (leaf rust) host Triticum vulgare PATHOGEN Puccinia triticina SYMPTOMS Pustules appear on the leaf ,on the upper surface. Pustule is orange brown in colour. Pustule have random arrangement They may group into patches Losses takes place between 5% and 20%

39. BROWN RUST OF WHEAT Diseased leaf

40. BROWN RUST OF WHEAT DISEASE CYCLE CONTROL MEASURES Use of fungicides is useful to control infections. Cultivars are the best method of controlling the disease. Variety resistance is important Wheat should be sown as early as possible to avoid rust periods.

41. BLACK RUST OF WHEAT (stem rust) host Triticum vulgare PATHOGEN Puccinia graminis tritici SYMPTOMS Pustules appear on the stem,leaf bases. Pustules have reddish brown colour Large number of uredo spores are released Towards the end black telia are produced

42. BLACK RUST OF WHEAT Uredospores Teleutospores

43. BLACK RUST OF WHEAT DISEASE CYCLE CONTROL MEASURES Use resistant varieties. Use of fungicides Cultivars is the method of controlling disease

44. YELLOW RUST OF WHEAT (stripe rust) host Triticum vulgare PATHOGEN Puccinia striiformis SYMPTOMS There is a appearance of yellow pustules on the upper surface of leaf. Pustules are round ,blister like and small Yellow coloured uredo spores are released

45. YELLOW RUST OF WHEAT

46. YELLOW RUST OF WHEAT DISEASE CYCLE CONTROL MEASURES Resistant varieties is the most effective method to control this rust. Use of fungicides C ultivars are also used to control disease

47. LOOSE SMUT OF WHEAT HOST Triticum vulgare PATHOGEN Ustilago tritici SYMPTOMS They bear loose, black ,powdery masses of smut spores instead of flowers. All the floral parts except the awns are converted into masses of smut spores. Membrane bursts and smut spore release Group of smut spore called sorus

48. LOOSE SMUT OF WHEAT Teliospores

49. LOOSE SMUT OF WHEAT DISEASE CYCLE CONTROL MEASURES Use of healthy seed for sowing Seeds are treated with the fungicide to kill any fungus which is present inside. Use of resistant varieties By heat treating the seed to kill the fungus before planting

50. RED ROT OF SUGARCANE host Saccharum officinarum PATHOGEN Colletotrichum falcatum Glomerella tucumanensis SYMPTOMS Appear after rainy season when plant growth stops In the early stage, yellowing and drooping of upper leaves is there In the later stage, the stem shrivels and loses its bright colour At advanced stage of disease blood red colour with dark margins develop on the midribs of the leaves

51. RED ROT OF SUGARCANE Sickle shaped conidia

52. RED ROT OF SUGARCANE DISEASE CYCLE CONTROL MEASURES By collection and burning of sugarcane trash in the field Crop rotation Use of resistant varieties is the most effective method of controlling the disease .

53. TIKKA DISEASE OF GROUNDNUT HOST Arachis hypogaea PATHOGEN Cercospora sp. Cercospora personata Cercospora arachidicola

54. SYMPTOMS Cercospora personata Leaf spots are small , more circular The mycelium consists of internal hyphae. The conidiophores occur on the lower surface of the host leaf The conidia are light in colour Cercospora arachidicola Leaf spots are larger in size ,and are irregularly circular. The mycelium consists of both external and internal hyphae. The conidiophores occur on the upper surface of the host leaf The conidia are pale yellow in colour

55. TIKKA DISEASE OF GROUNDNUT Conidia

56. TIKKA DISEASE OF GROUNDNUT DISEASE CYCLE CONTROL MEASURES By crop rotation By spraying fungicides Burning of the diseased plant debris will reduce the infection

57. ROOT KNOT OF VEGETABLE CROPS This disease is caused by root knot nematodes. Most of the vegetable crops serve as the host plant : carrot , sweet potato , okra , brinjal , chili , tomato etc.

58. ROOT KNOT OF tomato HOST Solanum lycopersicum PATHOGEN Meloidogyne sp. SYMPTOMS Leaf size decreases Yellowing of leaves Slow growth and dwarfing Yield reduces and it also kills the plant This root knot nematode produces root galls

59. ROOT KNOT OF tomato

60. DISEASE CYCLE

61. ROOT KNOT OF TOMATO CONTROL MEASURES ● Crop rotation ● Field sanitation ● Use of resistant varieties ● Deep ploughing ● Use of fungicides

62. EAR COCKLE OF WHEAT HOST Triticum vulgare PATHOGEN Anguina tritici SYMPTOMS Affects all growing stages There is a rolling and twisting of the leaves A rolled leaves traps the next growing leaf and inflorescence within it and causes it to become bent Base of the stem are bent and generally stunted.

63. EAR COCKLE OF WHEAT

64. EAR COCKLE OF WHEAT DISEASE CYCLE CONTROL MEASURES Use of healthy seed from healthy crop. Use of fungicides By crop rotation Hot water treatment of seed , first soaking seed in cold water for 4-5 hours and treating at 54C

65. KARNAL BUNT OF WHEAT HOST Triticum vulgare PATHOGEN Tilletia indica SYMPTOMS The fungus causes a reduction in the length of ears Not whole grain but partially are infected so, called as P artial Bunt Ovoid sori develop, containing dusty, brown to black spore masses.

66. KARNAL BUNT OF WHEAT sporangium

67. KARNAL BUNT OF WHEAT DISEASE CYCLE CONTROL MEASURES Use of healthy seed By crop rotation By spraying fungicides Use of resistant varieties

68. YELLOW VEIN MOSAIC OF BHINDI HOST Abelmoschus esculentus PATHOGEN Monopartite Begomovirus SYMPTOMS Yellowing of the entire network of veins in the leaf In severe infections younger leaves turn yellow ,become reduced in size The veins of the leaves w ill be cleared by the virus and intervenal area becomes completely yellow Virus is spread by whitefly

69. YELLOW VEIN MOSAIC OF BHINDI

70. YELLOW VEIN MOSAIC OF BHINDI DISEASE CYCLE The virus penetrates in the several hosts This virus is transmitted by whitefly The insect vector acquires virus , so viruses undergo incubation period of 7 hours within the vector body Further vector inoculates them on crop plants Vectors retain viruses in them and may infect host plant until they die CONTROL MEASURES By selecting varieties resistant to yellow vein mosaic. Organic neem oil is used to kill whitefly For sowing during the summer season ,when whitefly activity is high, the susceptible varieties should be avoided

71. LITTLE LEAF OF BRINJAL host Solanum melongena PATHOGEN Phytoplasma ( Mycoplasma like organism) SYMPTOMS There is a production of very short leaves by affected plant. The petioles are reduced in size L eaves are narrow, soft , yellowish Internodes are also reduced in size. This gives whole plant a bushy appearance Fruiting is rare

72. LITTLE LEAF OF BRINJAL Diseased leaf Diseased fruit

73. LITTLE LEAF OF BRINJAL DISEASE CYCLE Disease is transmitted from diseased to healthy plants by vectors. This is mainly transmitted by leafhoppers This leafhopper is inhabitants of brinjal leaves CONTROL MEASURES Removal of weeds and infected plants Spraying of insecticides Spray tetracycline which helps to control the disease. Use disease resistant varieties

74. CONCLUSION ● Plants are grown for beautiful flowers, fruits, seeds, vegetables but plants also affected by many diseases. ● Plant diseases cause great loses annually throughout the world and reduce the yield even with the use of improved varieties and technologies. Because of the dependence of humans for food, fiber and other resources, plant diseases and their control is vital for our survival. ● There is need to increase the productivity of crops for future generation to achieve the goal of sustainable development. ● Plant pathology is intimately related to the health of plant and production of more crop yield. ● Many new techniques and chemicals have been evolved to fight plant diseases. Efforts have been made to understand the nature of diseases at molecular levels and the relationship between host and pathogen.

75. REFRENCES Agrios , G.N. 2005. Plant Pathology . Elsevier Academic Press Vashishta , B.R. and Sinha , A.K. 2008 . Botany for degree students –Fungi. S . Chand and Company Ltd , New Delhi. Singh , R.P. 2005. Plant Pathology. Kalyani Publ., Noida. Mehrotra , R.S. and Aggarwal , A. 2013. Fundamentals of plant pathology. Tata McGraw Hill. Singh , R.S. 1970. Plant Diseases. Oxford and IBH Publ., CO. PVT. LTD. New Delhi.