*2.3.1 Distribution*

False smut or green smut is a common disease of rice caused by *Ustilaginoidea virens* in rice growing regions of India. Epidemics of false smut disease of rice were reported in Tamil Nadu in India and later in many countries of world [52]. Pannu et al., [53] also reported losses up to 44 per cent in Punjab. In Uttar Pradesh, yield losses up to 44 per cent were observed by Singh and Dube. In some rice growing districts of Bihar, 15–50 percent losses occurs due to false smut of rice when comes as medium to severe form [54]. The fungus overwinters in soil by means of sclerotia and chlamydospores. Sclerotia produces ascospores, which are primary source of infection to rice plants, whereas secondary infection may come from air-borne chlamydospores [55, 56]. Sclerotia can survive in the field for several months. Infection starts in grains of rice before flowering. Infection results in one or more kernels on mature heads of plants being replaced by globose, yellowish-green, velvety smut balls. When smut balls burst open, powdery dark green spores are released [57]. The infection of *U. virens* is favored by high relative humidity (>90%) and temperatures between 25 and 30°C [58]. Rainfall, high humidity, and soils with high nitrogen

#### *Integrative Advances in Rice Research*

content during flowering also favors disease development [59]. Reports on the effect of rainfall are conflicting, high disease intensity has been attributed to rainfall at heading, but the opposite (low rainfall favoring the disease) has also been reported [60]. The fungus attacks some of the weed species that commonly occur in rice fields and may also serve as sources of inoculums [57].

The pathogen specifically infects rice flowers and later transforms the grains into smut balls. Initially the balls are slightly flattened, yellow in color covered with a thin membrane. As the smut ball matures, it increases in size converting yellowishgreen to green or greenish-black. At final maturity, the entire smut ball looks dark black in color with rough surface. Very few grains in the panicle or all the grains may convert into smut balls (**Figures 9**–**12**).

## *2.3.2 Integrated management*

Select seeds which are free of smut balls for sowing. Avoid excess nitrogenous fertilizer application. Follow alternate wetting and drying of the field to avoid moisture build-up which helps in disease incidence. Remove and destroy infected panicles, crop debris after harvest. Identification of the stable and durable sources of resistance is always been the better option in disease management [56]. Large number of varieties have been screened and identified for their resistance or tolerance to false smut disease under artificial/natural inoculation conditions [60].

**Figure 9.** *Yellow ball covered with thin membrane.*

**Figure 10.** *The ball converting to greenish-yellow.*

*Emerging Minor Diseases of Rice in India: Losses and Management Strategies DOI: http://dx.doi.org/10.5772/intechopen.99898*

**Figure 11.** *The ball converted to black sori.*

**Figure 12.** *Heavily infected panicle.*

Artificial inoculation is still not dependable which is the major obstacle in screening large number of varieties under artificial conditions [56, 61]. Phenotyping for false smut resistance has been taken by many researchers in India, Philippines, China, Bangladesh, Pakistan and other countries by following standard evaluation system (SES) scale of IRRI (2002). In India, Kaur et al. [62] identified some of the hybrids namely VNR-211, GK-5025, HRI-140, IRH-74, PRSH-9018, KPH-467, RH-10428, 27P64 and KRH-4 showing complete resistance to false smut. Screening and identification of genotypes and QTL mapping is been carried out by pioneer rice research institutes in India such as National Rice Research Institute, Cuttack (Odisha), Indian Institute of Rice Research (IIRR), Hyderabad (Telangana), Punjab Agricultural Universty (PAU), Ludhiana (Punjab) and Indian Agricultural Research Institute (IARI), New Delhi. Identification of quantitative trait loci (QTL) and utilization in resistance breeding program is atmost priority in management of this disease [63]. Other management options like Seed treatment should be followed strictly: use carbendazim 50% WP @ 2 g/kg or biological control agents like *Trichoderma* or *Pseudomonas* talc based formulations @ 8–10 g/kg of seeds. Fungicidal spray with Propiconazole 25EC @ 500 ml/ha or copper hydroxide 77%WP @ 1.25 kg/ha at boot leaf initiation stage. Repeat the above spray at 50% flowering stage. Biological control of false smut disease has been successful with the strains of *Bacillus subtilis* in solution of Validamycine [64, 65].

#### **2.4 Grain discoloration/dirty panicle disease**

Pathogen: *Drechslera Oryzae, Sarocladium oryzae, Alternaria padwickii, Curvularia spp., Epicoccum sp., Fusarium moniliforme, Aspergillus spp.*

#### *2.4.1 Identification symptoms*

Seed discoloration has time and again proved to be a major recurring issue in the Indian coastal regions haltering the levels of desired grain production. Discoloration, though a minor disease in nature, has assumed a greater importance in agriculture owing to effect of global warming in production due to unpredictable hailstorms, delayed or low levels of rainfall, higher temperature and humidity levels after fowering stage. This has further led to relaxation in the procurement norms by the agencies. Grain discoloration serves as a visible indicator of seeds having lower quality in association with [66] microorganisms. This malady has been a prime retardant in the post-harvesting of paddy grains. The minimum threshold for the procurement of discolored kernels of paddy crop is kept at 3%, and all the samples above that are rejected. Several biotic and abiotic factors are responsible for discoloration of rice seeds. Glume discoloration is term for the alteration in color of mature seed from its original color, and seed possesses series of problems in seed certification programme. This disease though minor in nature reduces the vigor and yield of the crop and causes grain discoloration at maturity, thus reducing the economical and marketable value of the crop. The prevalence of monoculture and year around growth of only economical crops like paddy and wheat have led to seed discoloration gradually turning out to be a major problem [67]. This is also due to the many pests and pathogen that are common to both the crops. Since rice is a crop of immense importance, there is an increased need for research and development on various fungal fora that can afect the vigor, yield, morphology and constitution of the newly introduced higher yielding and aromatic rice cultivars. The reason for such discoloration whether pathological and/or non-pathological is not always clearly understood. In most of the cases, discolored rice seeds are frequently associated with micro-organisms, mainly fungi, though sometimes it also occurs due to insect bite and physiological or genetic reasons. Attempts have been made in the past to identify causal agents causing seed discoloration and also to control them by the use of chemicals. Grain discoloration is the early indication of poor yield and quality which leads to reduced market value. The discolored grain suffers more infection during storage also due to the development and infection of many storage fungi [68, 69]. Storage fungi such as *Aspergillus* spp. and *Fusarium* spp. produce deadly micotoxins which are detrimental to the human and animal health. Fungal pathogens such as *Alternaria alternata* (cause ashy gray discoloration) and *Helminthosporium oryzae* (cause black dicolration with dark brown spots on seeds) found mostly on the seed coat and endosperm region of the seeds. *Curvularia geniculata* which caused eye shaped spots, *Fusarium* spp. (*Fusarium oxysporum, F. moniliformae*) are responsible for pink discoloration and *Sarocladium oryzae* causes light brown discoloration. All these fungi found in embryo, seed coat and endosperm of the seeds [70]. Maximum colonization of seed borne fungi was observed in seed coat (0–3.30%) and endosperm (0.1–1.65%) as reported by Halgekar and Giri [71]. The losses due to grain discoloration were estimated approximately about 20–25 percent [72]. In our previous studies we reported that, the grain discoloration incidence ranged from 25 to 92% in different rice genotypes [73]. There may be a number of factors responsible for the disease starting from the varietal susceptibility, changed climatic conditions and agronomic managements which ultimately leads to the increased incidence of the disease with more damage.

*Emerging Minor Diseases of Rice in India: Losses and Management Strategies DOI: http://dx.doi.org/10.5772/intechopen.99898*

The disease is an important emerging problem in all the rice growing seasons. The type of infection may be external contamination by saprophytic pathogens or internally seed born where pathogens infects endosperm. There are different kinds of like ashy gray discoloration, black discoloration, pink discoloration and light brown discoloration based on the pathogens involved (**Figures 13**–**16**). The infected grains convert into dirty discolored grains which have numerous spots and lesions on them. Infection in field may transfer to storage where the pathogens multiply and produces some of the harmful toxins. The early infection in field leads to complete yield losses due chaffiness of the grains. The severe infection leads to rotting of the panicles leads to qualitative and quantitative losses.

#### *2.4.2 Integrated management*

Use disease free seeds. The seeds should also be free from damage, chaffiness and other deformities. Treat the seeds with carbendazim 50% WP @ 2 g/kg or biological control agents like *Trichoderma* or *Pseudomonas* talc based formulations @ 8–10 g/kg of seeds. At tillering and pre-flowering stage, spraying of carbendazim 50% WP @500 g/ha or copper oxychloride 50% WP @ 1 kg/ha will control the disease effectively. At boot leaf initiation stage, spray with Mancozeb 75% WP @ 1 kg/ha or Iprobenphos 48% EC @ 500 ml/ha or Carbendazim 50% WP @250 g/hac.

**Figure 13.** *Infected panicle.*

**Figure 14.** *Discolored grains.*

**Figure 15.** *Severe infection of the grains.*

**Figure 16.** *Chaffy grains.*

During grain maturity stage, spray with Mancozeb 75% WP @ 1 kg/ha or Iprobenphos 48% EC @ 500 ml/ha. Biological control agents like *Trichoderma atroviride* or *Bacillus amyloliquefaceance* talc based formulations @10 g/lit of water at grain maturity stage.
