33. Rice Blast and Their Losses

Introduction of Rice:

    Oryza sativa, commonly known as rice, is a crucial staple crop worldwide, particularly in Asia, where it provides a significant source of dietary carbohydrates and calories for roughly half of the global population. In addition to its nutritional value, rice serves as a vital economic crop in many countries, contributing to foreign income through exports. Each year, billions of tons of rice are consumed globally, with billions more being exported to various regions around the world.

• Rice is a grain that comes from either the Oryza sativa (Asian rice) or Oryza glaberrima (African rice) species. 
• There are more than 40,000 different varieties of rice, with Basmati, Thai Jasmine, and Italian Arborio being among the most popular.
• Interestingly, two Japanese car brands were named after rice: Toyota, which translates to "Bountiful Rice Field," and Honda, which means "Main Rice Field."
• Growing rice requires a significant amount of water, with approximately 5,000 liters needed to produce just one kilogram of rice.

1. Rice Blast:

Causal Organism:

    Pyricularia oryzae

Hosts and Symptoms:

    M. grisea is a pathogenic ascomycete fungus that can reproduce both sexually and asexually to produce specialized infectious structures called appressoria. These structures can infect aerial tissues, while hyphae can infect root tissues, making the fungus highly effective as a plant pathogen.

    Rice blast disease has been reported in various rice strains, including M-201, M-202, M-204, M-205, M-103, M-104, S-102, L-204, and Calmochi-101. Among these, M-201 is the most susceptible to infection.

• Leaf Blast: The crop is susceptible to fungal attacks throughout all stages of its growth, with visible signs of infection appearing on its leaves, nodes, rachis, and glumes. Lesions may start as tiny, bluish-green flecks on the leaves, which can expand during periods of high humidity to form spindle-shaped spots with a grey center and a dark brown margin. This symptom is commonly known as "Leaf Blast."

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  Nodal Blast: As the disease progresses, the spots on the leaves will merge, resulting in the drying and withering of large areas of the affected leaves. In addition to the leaves, spots may also develop on the sheath, and severe infections can cause the entire nursery or field to appear burnt. The fungus may also cause the formation of black lesions on the nodes, which can girdle and weaken them. This can result in the breakage of the affected nodes and death of the plant parts located above them, a symptom referred to as "nodal blast."
• Neck Blast: As the crop enters the flowering stage, the fungus can also infect the peduncle, causing the appearance of brownish-black lesions. This symptom is commonly referred to as "rotten neck," "neck rot," or "panicle blast" and is sometimes also called "neck blast."

    Early neck infection can result in the failure of grain filling, whereas late disease may only allow partial grain filling to occur. Additionally, small brown to black spots may be visible on the glumes of heavily infected panicles. The fungus can significantly reduce crop yields, with losses ranging from 30 to 61 percent depending on the stage of infection.

Pathogen:

• The mycelium of the fungus is typically hyaline to olivaceous in color and contains multiple septa. 
• Conidia, pyriform to ellipsoid in shape, are produced in clusters on long, septate, olivaceous conidiophores. These conidia have a broad base with a hilum and are typically 3-celled and hyaline to pale olive green in color. 
• The perfect state of the fungus, M. grisea, produces perithecia. The ascospores are hyaline, slightly curved, fusiform, and typically have 4 cells.

Favorable Conditions:

• Rice blast disease is favored by intermittent drizzles, cloudy weather, more rainy days, longer periods of dew, and high relative humidity ranging from 93-99 percent. 
• Additionally, low night temperatures below 26˚C or between 15-20˚C, the availability of collateral hosts, and excessive nitrogen can contribute to the development and spread of the disease. 
• To forecast rice blast disease, a combination of factors must be considered, including a minimum night temperature range of 20-26˚C, a high relative humidity of 90 percent or above, and these conditions lasting for at least one week during any of the three susceptible phases of crop growth: the seedling stage, post-transplanting tillering stage, and neck emergence stage. 
• The first leaf blast forecasting model in Japan was developed and known as BLAST.

Disease Cycle:

    Rice blast disease is primarily spread through airborne conidia, which are present throughout the year. The fungus can also be transmitted through infected straw and seeds, and irrigation water can carry conidia to different fields. Collateral hosts such as Panicum repens, Digitaria marginata, Brachiaria mutica, Leersia hexandra, and Echinochloa crusgalli can also serve as a source of survival for the fungus.

    When spores land on rice leaves, they can germinate, penetrate the leaf, and cause a lesion within four days. The fungus can produce more spores in as little as six days. Infections that result from spores arriving from a distance are known as primary infections, which typically result in a few scattered spots on leaves. However, spores that arise from primary infections can lead to many more infections, a process known as the secondary spread. Secondary spread is responsible for the severe epidemics of rice blast disease in fields and localized areas.

Management:

• To prevent disease in crops, it's recommended to cultivate moderately resistant varieties such as CO47, IR 20, ADT36, ADT39, ASD 18, and IR64, while avoiding highly susceptible varieties like IR50 and TKM6 during disease-prone seasons. 
• It's also important to remove weeds from the field bunds and channels.
• Treating seeds with Captan, Thiram, Carbendazim, Tricyclazole, or Pseudomonas fluorescens at a rate of 2 g/kg can help prevent disease. In the nursery, spraying with Carbendazim (500mg/L) or Tricyclazole (300mg/L) is recommended.
• To protect the main field, it's advisable to spray with Edifenphos (500 ml), Carbendazim (500 g), Tricyclazole (500 g), or Iprobenphos (IBP) (500 ml/ha).

Global Losses:

• Scenario three analysis showed that an average of $69.34 million is lost annually to blasts in the Mid-South of the US, due to yield loss and mitigation costs.
• If the maximum infection rate of 46.95% is applied to susceptible hectares, the potential economic loss is estimated to be $203.49 million annually.
• The calculated potential economic loss as a share of the total value of rice production in Mississippi, Louisiana, and Arkansas is estimated at 3.98%, 4.02%, and 4.92%, respectively.
• The total value of rice production data was obtained from USDA and converted to 2014 dollars using annual CPI retrieved from IMF.
• Overall, the potential economic loss for scenario three is estimated at 4.08% as a share of the total value of rice production in the Mid-South of the US.
• The rice blast caused by Magnaporthe oryzae is a significant threat to global food security, resulting in around 30% of rice production losses worldwide.
• These losses have a direct impact on consumer welfare and increase the global price of rice, which can adversely affect food security.

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20. Rice Production Technology

 Rice

Scientific Name:

Oryza sativa L.

Rice Botany:

• It's miles a self-pollinated plant. 
• It produces four to five tillers. 
• The stem or culm is hollow, erect, and accessible. 
• It consists of nodes and internodes. 
• The leaf consists of a long, slim leaf blade and a loose-leaf sheath with generally long ligules. 
• The inflorescence is unfastened, with many-branched panicles, every bearing many spikelets. 
• The root system is shallow and consequently concentrates in the topsoil layer to an intensity of 20 to 25 cm. 
• It consists of seminal or seed root, and adventitious root, arising from nodes close to the soil surface. Safe-to-eat seeds are borne in a dense head (called panicle) on separate stalks. It's miles a long day plant that's self-pollinated.

Economic Importance of Rice:

• It's by far the critical meal crop of the world and is the staple meal in South East Asia at present extra than half of the global populace relies upon this crop for its nutritional wishes. It occupies 2nd function after wheat in Pakistan and plays an important position in Pakistan’s economic system as billions of bucks are earned yearly by its export. 
• In Pakistan, all through the year 2018-19 its region is 2.8 million ha with a total manufacturing of 7.20 million tons with an average paddy yield of 2562 kg/ha.

Production Technology of Rice:

• The nursery must not be sown before 20 May to prevent the rice from the attack by insects.
• Super Basmati, Basmati 385, PK 386, and Chenab Basmati these varieties have the time of sowing for their nursery is 1st June-20 June and the time of planting for this is 1st July-20 July.

Methods for nursery sowing:

These the following three which discussed given below:

• wet bed method
• Dry bed method
• Raab method

Wet bed method:

• Soak the seed in water for twenty-four hours, after that cover the source with moist jute bags and area it beneath the shade.
• The seed will germinate after 36-forty eight hours.
• Irrigate, plow, puddle, and degree the sector.
• Put together beds of 1 to 1.5 m width, 4-five cm height & any convenient period.
• Germinated seed is sown with broadcast technique @ 1kg/Marla for ARRI sorts and @ 500-750g/Marla for Basmati types.
• 1-1. Five-inch water should be a gift before broadcasting the pre-germinated seed at night.
• Drainage the water the next night and irrigate it in the subsequent morning. Repeat it for one week.
• Preserve a water level of two-5 cm, depending on the peak of seedlings.
• If the seedling weakens, observe urea 250g in line with Marla.
• Seedlings might be ready for transplanting in 25-30 days.
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Dry Bed Method:

• Practiced wherein puddling is not possible as soils are loamy or silt loam.
• The plot is ready in water situations after irrigation.
• Dry seed is sown with broadcast method @ 1.5 kg/Marla for ARRI varieties and 750g/Marla for Basmati varieties.
• The straw layer is spread and irrigation is implemented.
• The straw layer is eliminated after some days to facilitate sunlight.
• The seedling might be ready in 35-40 days.

Raab method:

• Practiced in areas of D.G. Khan and Muzaffargarh wherein soil is challenging.
• The uprooting of the nursery is tough.
• Nursery plots are leveled.
• Crop residues (5cm layer) spread uniformly and burnt.
• Ash is pressed on the soil after cooling.
• Dry seed is sown with broadcast approach @ 2kg/Marla for ARRI sorts and @ 1kg/Marla for Basmati varieties.
• The seedling can be prepared in 35-40 days.
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Land Preparation for Transplanting:

• Irrigate the sector until the status water situation is a minimum of three days before puddling.
• In wetlands, a waterproof layer is created at an intensity of about 20cm.
• Degree the sphere during puddling.
• Use ‘Raja Hal” in high clayey soils with more water availability earlier than puddling.
• Transplant the nursery as quickly as feasible after area guidance.
• Puddling isn't always executed in salt-affected soils as salts will no longer leach down.

Transplanting:

• Seedling age needs at most 30-forty days on the transplanting.
• Irrigate the sector 1-2 days before uprooting the seedling as it facilitates the uprooting.
• Transplanting must be executed in 1. Five-inch-deep water.
• Maintain water depth at 1.5 inches for the first week of transplanting annat at 3 inches.
• Do now not use damaged or diseased flowers for transplanting.
• Use two flora in keeping with hollow with a nine × 9-inch distance.
• As 80000 holes and 160000 plants in line with acre.
• Location some seedling bundles near field banks in water to refill the gaps in 7-10 days’ length.

Fertilizer Application:

• IRRI-6, KS282, KSK133, and KSK 434 when sown after wheat then apply N 69, P 41, K 32 form urea, SSP, and K2SO4. 

Irrigation:

• Standing water has to be present in the rice field for 25-30 days after transplanting.
• Water intensity must be 1-2 inches.
• Stop irrigation before 15 days of ripening.

Measures for Plant Protection:

• All weeds should be removed within a month after transplanting.
• Weeds reduce the yield and deteriorate the high quality.
• The crop rotation method allows governing weeds.
• Keep the water stage up to three inches for 30 days if available.
• Use recommended herbicide 3-five to days after transplanting.
• Consult the rural professionals for endorsed herbicides.
• Do now not let the sphere dry for one week after the herbicide utility

Diseases Treatment:

• Use sickness-resistant sorts.
• Treat the seed with encouraged fungicide.
• Burn the crop residues after harvesting.
• Concern the agriculture workforce for in addition steerage.

Insect Control:

• Damage the insect eggs and nymphs.
• Use alternative plant life or weeds for insect feed.
• Biological manipulation techniques also can be used.
• The light trapper can also help to govern bugs.
• Crop rotation can reduce the probability of insect attack.
• Use suitable insecticides for bugs.

Harvesting of Rice:

• Timely harvesting is essential for optimum yield.
• 20-22% moisture in grain is an excellent time for harvesting.
• After harvesting yield must be reached in the market well timed.
• Save the product after 4-6 days of drying (at 12-13 % moisture).
• Traditional harvesting is an extra complex and time-eating method.
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Rice Varieties:

    Pakistan is one of the most important manufacturers and customers of rice. A number of the generally grown and fed rice sorts in Pakistan include:

1. Basmati Rice - a protracted grain, fragrant rice with a sensitive taste
2. IRRI Rice - medium grain rice, broadly grown inside the Indus Valley area
3. D-98 Rice - an excessive-yielding type of IRRI rice, regarded for its company texture
4. PUSA Basmati Rice - a diffusion of Basmati rice with an exceptional aroma and flavor
5. Kainat Rice - a hybrid variety of Basmati rice, recognized for its outstanding cooking first-rate
6. Splendid Basmati Rice - a high-yielding form of Basmati rice, regarded for its lengthy grain length.

    These are a number of the famous rice varieties grown and consumed in Pakistan.

NOTE:

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