Macrophomina phaseolina ppt

PLANT PATHOGEN AND DISEASE
MSC MICROBIOLOGY 2ND YEAR

1. Sub- Microbial ecology topic- PLANT DISEASES

2. PATHOGEN- MACROPHOMINA PHASEOLINA DISEASE- CHARCOAL ROT PRESENTED BY- SHARON MARIAM ABRAHAM M.Sc. MICROBIOLOGY 2 nd YEAR

3. Macrophomina phaseolina   Macrophomina phaseolina is a soil- borne fungus that primarily causes “Charcoal rot”. It is one of the most harmful seed & soil borne pathogen fungus that infects nearly 500 plant species in more than 100 families.

4. HOST PLANTS Peanut Cabbage Chickpea Soybean Sunflower Sweet potato & Potato Alfalfa Sesame Sorghum, Wheat, and Corn

5. DISEASES CAUSED BY THE FUNGUS INCLUDE: Damping off Seedling blight Collar rot Stem rot Charcoal rot Basal stem rot Root rot

6. SYMPTOMS The pathogen  M. phaseolina  affects the fibrovascular system of the roots and basal internodes of its host, impeding the transport of water and nutrients to the upper parts of the plant. As a result, the characteristic symptoms of the fungal infection include: Progressive wilting Premature dying Loss of vigor Reduced yield

7. CHARCOAL ROT ONSET During or after flowering, Grey discoloration of the stem and taproots, Shredding of plant tissue in the stem and top of the taproot, and Hollowing of the stem are observed. Small black dots may form beneath the epidermis of the lower stem and in the taproot, giving the stems and roots a charcoal-sprinkled appearance. When the epidermis is removed, small and black microsclerotia (a sign of the disease) may be so numerous that they give a greyish -black tint to the plant tissue.

8. Sclerotia of  Macrophomina phaseolina  on mung bean. ( Sclerotia (Single- Sclerotium ); is a compact mass of hardened fungal mycelium containing food reserves).

9. DURING UNFAVOURABLE CONDITIONS The fungus has aggregates of hyphal cells, which form microsclerotia within the taproots and stems of the host plants. The microsclerotia overwinter in the soil and crop residue and are the primary source of inoculum in the spring. Microsclerotia are black, spherical or oblong structures that allow the persistence of the fungus under poor conditions, such as low soil nutrient levels, low (winter) and high temperatures (above 30 C).

10. These have been shown to survive in the soil for up to three years under favorable conditions. However, in wet soils, microsclerotia survival is significantly lower, often surviving no more than 7 to 8 weeks, and mycelium cannot survive more than 7 days. The fungus- infected seeds carry the organism in the seed coat and do not germinate or produce seedlings that die soon after emergence.

11. INFECTION Macrophomina phaseolina has a monocyclic disease cycle. It usually attacks the plant during stress conditions like drought. The fungus itself favors growth under low water potential (not very wet soil conditions) and relatively high temperatures. Germination of the microsclerotia occurs throughout the growing season when temperatures are between 28 and 35 C.

12. DURING FAVORABLE CONDITIONS Hyphae germinate from these microsclerotia on the root surface, and germ tube forms appresoria that penetrate the hosts' epidermal cell walls using turgor pressure or through natural openings. Initially, the hyphae enter the cortical tissue and grow intercellularly , then infect the roots and the vascular tissue. Within the vascular tissue, mycelia and sclerotia are produced and these plug the vessels.

13.  This causes the greyish -black color often observed in plants infected by  M. phaseolina , and it also prevents water and nutrients from being transported from the roots to the upper parts of the plant. Thus, due to this systemic infection, diseased plants often wilt and die prematurely

14. Macrophomina phaseolina on a culture plate

15. MANAGEMENT OF THE FUNGUS FUNGICIDES: Inhibit mycelial growth. Most powerful active ingredients/ fungicides are Carbendazim & Penflufen + Trifloxytrobin . ORGANIC METHODS: SOIL SOLARIZATION: Use of solar power for controlling pathogens in the soil by mulching the soil (to trap moisture) and covering it with a large, usually transparent polyethylene tarp to trap solar energy and heat the soil

16. CROP ROTATION: Studies have shown that Corn is not as a good host as Soybean for M. phaseolina . Thus, rotation of crop every 3 years can decrease the seed and soil contamination by the microslerotia .