Cattaneo from Italy published the first description of stem rot or sclerotial disease in 1876. Since then, reports of it have come from a number of rice-growing nations, including Japan, the United States, Ceylon, Burma, Vietnam, the Philippines, and China. In India it was first observed in Bengal in 1911. Butler later documented the condition in full a year later, in 1918. Since then, the majority of states that farm rice have reported it. Damage varies depending on the tract and possibly depending on the season. Stem rot of rice is caused by **Sclerotium oryzae**¹. It is one of a number of organisms that can damage rice leaf sheaths and/or stems. Others are listed in the “Rice field guide to pests, diseases and weeds”¹. The fungus infects the leaf sheath, leading to leaf death and rotting of the stem¹. Source: Conversation with Bing, 15/9/2023 (1) https://en.wikipedia.org/wiki/Magnaporthe_salvinii#:~:text=Magnaporthe%20salvinii%20%28%20teleomorph%29%2C%20also%20known%20as%20Sclerotium,small%2C%20black%2C%20irregular%20lesion%20on%20the%20leaf%20sheath.. https://en.wikipedia.org/wiki/Magnaporthe_salvinii. (2) AN OVERVIEW OF STEM ROT DISEASE OF RICE (Sclerotium oryzae Catt.) AND .... https://www.fortunejournals.com/ijabpt/pdf/96010-K%20Gopika.pdf. (3) Induced tolerance against stem-rot disease of low-land ... - Springer. https://link.springer.com/article/10.1007/s42161-021-00948-5. (4) Pathogenic and Molecular Variability in Sclerotium Oryzae Catt.. https://chesci.com/wp-content/uploads/2021/08/v10i39_8_cs122052031_367-371.pdf. https://vikaspedia.in/agriculture/crop-production/package-of-practices/cereals-and-millets/paddy/rice Sclerotium oryzae is a fungus that causes stem rot of rice. It is a major disease of rice in tropical and subtropical regions. The fungus can survive in soil for several years and can be spread by infected seeds, water, and farm implements. The symptoms of stem rot of rice vary depending on the stage of growth of the plant. In young seedlings, the fungus can cause damping-off, which is the death of the seedlings at the soil level. In older plants, the fungus can cause the stems to rot and the leaves to wilt. The infected plants may also produce fewer grains. To control stem rot of rice, a combination of cultural and chemical methods can be used. Cultural methods include: * Planting resistant varieties of rice * Avoiding waterlogging * Rotating crops * Burning crop residues Chemical methods include: * Applying fungicides to the soil before planting * Treating the seeds with fungicides * Applying fungicides to the plants during the growing season If you suspect that your rice plants have stem rot, it is important to consult with a plant pathologist for diagnosis and treatment. * The fungus is a white, cottony mass that can be found on the stems and leaves of infected plants. * The fungus produces spores that can be spread by wind, water, and insect

1. STEM ROT OF RICE - Sclerotium Oryzae Catte
Magnaporthe salvinii (Teleomorph)
INTRODUCTION
Cattaneo from Italy published the first description of stem rot or sclerotial disease in
1876. Since then, reports of it have come from a number of rice-growing nations, including
Japan, the United States, Ceylon, Burma, Vietnam, the Philippines, and China. In India it was
first observed in Bengal in 1911. Butler later documented the condition in full a year later, in
1918. Since then, the majority of states that farm rice have reported it. Damage varies
depending on the tract and possibly depending on the season.
Magnaporthe salvinii is an ascomycete fungus that infects a plant in a polycyclic
manner. Sclerotium oryzae is a fungal pathogen that causes stem rot disease in rice plants.
This disease is a significant concern in rice cultivation, leading to about 35% crop loss. The
pathogen has different morphological variations in its life cycle, including sclerotium,
perithecium, and conidium. Sclerotia are macroscopic balls of fungal tissue that persist for a
long time in unfavorable conditions. They are the chief infectious agents of S. oryzae and are
found scattered in old rice straw and on the soil after harvest.
CAUSAL ORGANISM : Sclerotium oryzae Catt., (1879)
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Subclass: Sordariomycetidae
Order: Magnaporthales
Family: Magnaporthaceae
Genus:Magnaporthe
Species: M. salvinii
TELEMORPH: Magnaporthe salvinii (Catt.) R.A. Krause & R.K. Webster, (1972)
PERFECT STAGE: Leptosphaeria salvinii Catt., (1879)
CONIDIAL STAGE: Helminthosporium sigmoideum var. irregulare Cralley & Tullis, (1935)
The genetic connection between S. oryzae and L. salvinii, an ascomycetous fungus whose
conidial stage is H. sigmoideum, was shown by Tullis in the United States in 1953.
SYMPTOMS
a) The disease appears in the late stages of plant development. The principal indication
of the disease is an excess of late tillers at the stem's base, which turns discoloured
and rotting in severe cases.

2. b) The emergence of tiny, black, irregular lesions on the outer leaf sheath at the water
line is the first symptom of the disease.
c) The discoloration extends up and down from the water line as the sickness progresses.
d) The interior of the culm may be filled with grey fungal mycelium when the infected
plants are cut apart and examined.
e) Numerous sclerotia might be discovered inside the culm or implanted in the host
tissue.
f) The plants that are harmed produce ears with lighter grains. Seedlings are also
impacted, resulting in leaf dryness. On the withering older basal leaves, masses of
sclerotial bodies can be detected.
g) In the main field, infected plants collapse owing to stem base weakness, and as the
illness progresses, the basal stem up to around 2-3 inches becomes dark green, and
the tissues within may rot.
PATHOGEN
a) The mycelium in the sclerotial stage is composed of extensively branching white to
greyish hyphae that are 4-8 µ thick and produce sclerotia that are nearly spherical,
smooth, black, and shiny, measuring around 200-350µ in diameter and visible to
the naked eye as black spots.
b) Sclerotium oryzae is phobic, buoyant, and uniform in size
c) Perithecia at the ideal stage are globose, each capped with a short cylindrical beak,
350-400 µ, in diameter, with clavate asci bearing 8 ascospores, the spores
measuring around 60 x 9 µ, are three septate, and pale yellow in colour.
d) Conidiophores are erect and nodular in the conidial stage, with 8-10 septa bearing
falcate to sigmoid, three septate, pale olivaceous conidia measuring 55-65 x 11-14
µ.
e) The fungus's imperfect stage can be found both inter- and intracellularly in the host
tissues.
f) Morphology of the sclerotia can be used to distinguish between S. oryzae and S.
oryzae var. irregulare.
DISEASES CYCLE
a) During the off-season, the fungus's sclerotia thrive in soil and stubble and serve
as the principal source of inoculum.
b) Sclerotia are present in the upper 5-8 cm of soil in the field and float on the
surface of water when the fields are flooded.
c) Sclerotium oryzae is a necrotrophic pathogen, which means it applies brute
force during invasion by secreting potent tissue-degrading enzymes or toxins.
d) They are carried from field to field by irrigation or flood water, accounting for
secondary disease dissemination.
e) They sprout quickly in the presence of enough soil moisture. Sclerotia survive
in dry soil for several months before becoming active in the following cropping
season.
f) When conidia are generated, they contribute to the spread of the disease.

3. FACTORS INFLUENCING DISEASE
a. This is a weak pathogen that only becomes active under favourable conditions.
b. Severe outbreaks of the illness have been linked to plant weakness caused by
physiological imbalance, unusual dryness, or insect attack, specifically stem
borer incidence. Plant lodging hastens disease transmission.
c. While several writers have reported success in infecting rice plants with the
fungus through artificial inoculation, the mere presence of sclerotial bodies in
soil does not appear to induce any meaningful incidence of the disease in the
field.
d. Application of nitrogen and phosphorus fertilizers to soil, either individually or
in combination, increases the disease intensity. Potash effectively counters the
harmful effects of nitrogen and phosphorus.
INTEGRATED DISEASE MANAGEMENT SPECIFIC TO BIOCONTROL
a) Controlling the disease is challenging since sclerotia can live in the soil for lengthy
periods of time.
b) Burning the stubble left in the contaminated field is beneficial but difficult to
implement, especially when rice is grown in rainy conditions.
c) Draining the irrigation water and leaving the soil to dry appears to be the greatest
approach for controlling the disease when done carefully. Furthermore, soaking the
soil with 0.1 per cent Ceresan after draining the water three times during the growing
season in the main field has been shown to effectively control the disease.
d) Balanced manuring aids in the control of the disease. Irrigation water should never be
directed from an affected field to an uninfested field.
e) Stem rot in rice can be controlled through the use of biological control agents. Some
important biocontrol agents for stem rot include Pseudomonas fluorescens,
Pseudomonas aeruginosa, Bacillus subtilis, and Bacillus pumilus.
f) These agents can be applied through direct inoculation, such as dipping seeds in
culture or aerial spraying, or by using solid-phase inoculants.
g) Additionally, formulations of these biocontrol agents, such as those containing methyl
cellulose and talc, have shown satisfactory results in suppressing stem rot.
h) However, it is important to note that commercially available biocontrol agents for rice
disease control are currently limited.
i) One such method is the use of microbe-based biofertilizers, which can control the
pathogenic activity of S. oryzae by exploiting, competing, or exhibiting antibiosis
against the fungus
j) The combined use of butachlor mix in soil and propiconazole spray at 400 ppm and
100 ppm, respectively, after pathogen inoculation followed by introduction of T. viride
and P. fluorescens, just as disease symptoms appeared, was found to be highly
effective in controlling disease spread and even beneficial in promoting rice plant
growth.

4. k) Biocontrol using Trichoderma is mentioned as an alternative and cost-effective method
for controlling stem rot. This approach can help reduce the reliance on fungicides,
which can have negative environmental and health effects
l) The document mentions the use of various fungicides for stem rot management, such
as hexaconazole, propiconazole, butachlor, and carbendazim. These fungicides can be
applied at different stages of the disease to reduce its incidence and severity.
m) Inorganic fungicides like potassium fertilizers, benzoic acid, and naphthalene acetic
acid have been found to induce resistance against stem rot in rice plants. However, the
negative impacts of these chemical substances on the environment and other
organisms are also acknowledged.
n) Cultural practices like proper management of rice residues, crop rotation, and
polyethylene mulching of soil have been suggested to reduce the viability and growth
of Sclerotium oryzae, the causal agent of stem rot