Lecture 10b: Plant-Pathogen Fungi and OOmycetes Flashcards
Major types of plant diseases
Vascular wilts
Leaf spots
Smuts and Rusts
Root rots
Crankers
Galls
Mildews
Soil-borne pathogens
Vascular wilts and root rot diseases
Vascular wilt diseases
Blockage of xylem vessels, impending water transport
Fungal causal agents and symptoms of vascular wilt disease
- Fusarium oxysporum
- Verticillium albo-atrum
- Verticillium dahlia
Symptoms: - Progressive yellowing of the leaves
- Early
Panama wild
Host: Banana and plantain
Pathogen: Fusarium oxysporum
first reported in Australia
Symptoms of Fusarium wilt of banana
- Chlorosis and death of oldest leaves
- Yellowing and wilting of leaves
- Young leaves develop symptoms and skirt the stem
- Plant collapse
- No symptoms on fruit
Fusarium wilt of banana disease cycle
- Infection of young fleshy/wounded roots
- colonisation: Proliferates up into the xylem vessels and produces spores that act as second inoculum
- Survival: Chlamydospores are produced when the plant dies. They germinate under favourable conditions and the cycle is repeated
- Pathogen introduced to plantation when planting infected material
Epidemiology of Fusarium wilt of bananas
- Polycyclic disease (more than one infection cycle per crop cycle)
Pathogen dissemination of fusarium banana wilting
- Infected rhizomes
- Surface water
- Poor sanitation practices
- Banana weevil
Management of Fusarium wilt of banana
- Pathogen exclusion
*Rapid containment of affected sites (destruction of symptomatic and surrounding plants) - Disease-free tissue planting material
- Resistant cultivars
Smut diseases
- Affect members of the family Poaceae: maize, wheat, sugarcane and sorghum
- Fungal spore accumulate in sooty-like masses, formed within ‘blisters’
Sugarcane Smuts host and pathogen
Host: sugarcane
Pathogen: Sporisorium scitamineum
Favoured environment of Sporisorium scitamineum
Long, dry and warm winters followed by good spring rains
Symptoms of Sugarcane smut diseases
- Black whip-like structures develop from tops of infected shoots
- Shortening and crinkling of spindle leaves, and elongated internodes
- Infected plants are stunted
- Thin stalks with grass-like appearance
Disease cycle of Sugarcane smuts
- Transmission: airborne teliospores, vegetative propagation of infected canes, infected plant debris or soil
- Infection: Teliospores deposited at the leaf and the sheath junction; travel to the bud
Moisture required for teliospore germination
Basidiospores fuse to form dikaryon, which germinate to produce hyphae
Infection of meristem tissue
Epidemiology of sugarcane smuts
- spore adapted to aerial dispersal
- Spore survival in soil about 2-3 months
- Requires living host plant to produce spores
Management of sugarcane smuts
- Resistant sugarcane varieties
- Disease-free seedcane (Hot water treatment/ fungicide application)
- Rogue infected stools, plough out severely smutted flieds
Host and pathogen of cob and tassel smuts
Host: Maize
Pathogen: Sphacelotheca reiliana
Symptoms of cob and tassel smuts
- ear infections: round and swollen, lack silks, black powdery spore mass
- Tassel infections: Few spikelets to entire tassel, leafy structures
- Other symptoms: aborted ears, stunting, excessive tillering
epidemiology of cob and tassel smuts
- Soil-borne
- Teliospores = wind dispersal
- Condition optimal for maize germination: 21 DC, moderate to low soil moisture
Management of cob and tassel smut management
- Resistant hybrids
- Sanitation systems: crop rotation, burning infected plants
- Planting later, in high soil temp and frequent rainfall
- Fungicide seed treatment
- Quaratine
