Survey on the Status of Post Flowering Stalk Rots in Telangana State

Author: M. Bhavani*, B. Mallaiah, D. Bhadru, M. Prameela and S. Vanisri

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Abstract

Post-flowering stalk rots (PFSR) are complex and one of the economically important diseases of maize. The PFSR incidence has been increasing in most of the maize growing areas of Telangana. A roving survey was conducted during Kharif -2021 for maize plants with typical symptoms of PFSR in major maize growing areas of Telangana state. Samples were collected from 30 villages in 9 districts. Disease incidence varied from 1.66 % to 48.52% in different villages. The maximum disease incidence was reported in Porandla (Thimmapur) village of Karimnagar district and minimum disease incidence was recorded in Appajipally (Balanagar) village of Mahabubnagar district. Pathogen associated in all the samples were isolated and morphologically identified as Fusarium verticillioides in 17 samples and Macrophomina phaseolina in 13 samples. The disease incidence was high in red soils compared to black soils. Hence, this kind of surveys help in timely identification of associated pathogen and take up necessary IDM measures to overcome the disease incidence.

Keywords

Post flowering stalk rot, Fusarium stalk rot, Charcoal rot, survey, samples

Conclusion

The present study concludes that generally stalk rot of maize is present in almost all the surveyed maize fields with variable intensities. Karimnagar, Warangal, Khammam are among the predominant areas with respect to severity of stalk rot of maize. F. verticillioides and M. phaseolina are responsible for stalk rot of maize in Telangana. Therefore, similar kind of studies should regularly be carried out in different maize growing areas to assess the status of PFSR and making suitable management strategies for future.

References

INTRODUCTION Maize (Zea mays L.) is one of the important and third largest grown cereal crop in India after paddy and wheat. Currently, nearly 1162.7 million MT of maize is being produced together by over 170 countries from an area of 201.8 million ha with average productivity of 5.75t/ha (FAOSTAT, 2020) accounting for ~9% of total food grain production. In India, it was cultivated in an area of 9.891 Mha during 2020-2021 with a production of 31.65 MT and productivity of 31.99 q/ha. In Telangana state, the crop is grown in almost all districts in an area of 259 thousand hectares with a production of 1756.57 thousand tonnes and productivity of 6782Kg’s/ha (INDIASTAT, 2020- 2021). In India nearly 61 diseases are infecting maize. Among them stalk rots are one of the economically important diseases of maize all over the world (Payak and Sharma 1985). Post-flowering stalk rots (PFSR) are complex disease, which are widely distributed in almost all the maize growing regions across the world. A number of fungi are involved in decaying pith causing pre-mature wilting of the plants (Shekar et al, 2006). In India three bacteria and eight fungi were reported to cause stalk rots (Raju and Lal 1976). Stalk rot disease caused by fungal pathogens are the most destructive disease of maize (Munkvold, 2003). Among all Fusarium stalk rot (F. verticillioides), Charcoal rot (M. phaseolina), Late wilt (Cephalosporium maydis) are more destructive in nature (Khokhar et al., 2014). However, predominantly M. phaseolina and F. verticillioides incidence were high in Telangana. Generally stalk rot occurs in areas where drought conditions prevails at or after flowering. The disease is favoured by high soil temperature (30oC to 42oC) with low soil moistures. In a field survey conducted in 2019-2020 in Telangana the disease incidence ranged from 27% to 76.8% with a yield loss of 30% (Mamatha et al., 2020). MATERIALS AND METHODS Survey. The survey for stalk rot of maize was conducted during Kharif-2021, in 30 villages of 9 districts. Survey was typically conducted when crop was at physiological maturity stage and stalk rot symptoms were likely to appear (Kelly et al., 2017). In each village, five fields were selected with 10 km distance apart. Data regarding GPS, soil type, crop stage, previous crop sown, source of irrigation, crop variety, agronomic practices followed by farmer were recorded. Sampling procedure. The disease incidence was recorded by enumerating the number of wilted plants out of total number of plants in a 4m × 4m area of the field at all the four corners and in the centre (Ramesha, V and Krishnan, 2017). Disease incidence percentage was calculated by using the formula Disease incidence (%)=(Number of infected plants )/(Total number of plants) × 100 Diseased stalk sections were packed in paper bags, labelled and brought to the laboratory for isolation and identification of associated fungal pathogens. Diseased samples were examined under light microscope and infected stems with typical stalk rot symptoms were processed further. Isolation . The plants with typical symptoms were first washed with tap water followed by sterile distilled water. Three 5 mm diseased stalk bits were taken at 5, 10 and 15 cm from the first internode above the brace roots (Scauflaire et al., 2011). Diseased portions were cut into small bits of 3-5 mm size, surface sterilized by dipping them in sodium hypochlorite (1%) solution for one minute and then 3-4 bits were transferred aseptically to petri plates containing Potato dextrose agar (PDA) medium that was amended with streptomycin sulphate to inhibit bacterial growth and were incubated at 25 ± 2ºC in BOD incubator. The pathogens isolated from the infected tissue were further purified by single spore isolation method as described by (Ho and Ko 1997) and identified based on cultural and morphological characters. RESULTS AND DISCUSSION In Telangana, disease prevalence was observed in almost all the surveyed villages ranging from 1.66 % to 48.52% in different districts. The highest disease incidence (48.52%) was recorded in Porandla village of Karimnagar district followed by Rajendranagar village in Rangareddy district with 42.42% disease incidence while the lowest recorded in Appajipally village of Mahabubnagar district (Table 1). The disease incidence was high in red soils (1.66% -48.52%) than in black soils (14-42.4%)under rainfed conditions than in irrigated conditions. Variation in incidence and severity of stalk rot disease at different locations might be attributed to variation in various soil and environmental factors, time of irrigation, rainfall, cropping patterns, variety grown, management practices followed in the locations (Doohan et al., 2003; Scauflaire et al., 2011). It was found that samples from Vikarabad (Dharur), Nizamabad (Morthad), Karimanagar (Kondapaka), Warangal (Kurchapalle), Mahabubabadh (Nadivada, Bayyaram), recovered F. verticillioides and samples from Mahabubnagar (Jadcherla), Karimnagar (Choppadhandi) reported only M. phaseolina isolate while samples from Khammam (Kothagudem, Konijerla), Karimnagar (Ramakrishnapuram, Porandla, Medipally), Siddipet (Pragnapur), Rangareddy (Rajendranagar), Warangal (Chagal, Dharmasagar, Velair), Mahabubnagar (Peddharevalle) reported both F. verticillioides and M. phaseolina indicating their complex nature in soil. Maize plants showing characteristic Fusarium stalk rot symptoms includes rotting that extend from infected roots to the stalk and causes premature drying, ear dropping, stalk breakage. Thus reducing maize yields significantly (Hooda et al., 2018). The disease causes internal tissue decay, vascular tissue discolouration, blocking translocation of nutrients and water and resulting in lodging and death of the plant and Charcoal stalk rot symptoms which ranged from seedling blight, rotting of stalk, roots and kernels. It produces brown, water soaked lesions on the plant roots which later gives black discolouration (Thahir et al., 2019). As the plants fungus spread into the lower internodes of the stalk, causing, shredding (Fig. 1), premature ripening and breaking at the crown. Interior stalks gave a charred appearance because of numerous black sclerotia in vascular strands (Fig 1) (Kaur et al., 2008). Sclerotia is found just under the stalk surface and also on the roots. The fungus infects the kernel by turning them black (Shekhar et al., 2006). Gum deposition was observed in the cortical tissues of roots were randomly sampled from each location. These results are in agreement with the (Mamatha et al., 2020) reported that maximum disease incidence was noticed in Karimnagar district because of favourable conditions prevailing during flowering compared to other districts in Telangana. Also (Munkvold, 2003) reported that cultural practices and geographical location including tillage, planting date, crop rotation and fertilizer application also affect the disease incidence of all Fusarium spp causing stalk rot of maize. Also (Khokhar et al., 2014) reported that late sown crop and hot and humid weather favours the disease development more because of heavy inoculum built up in the soil and moisture stress during flowering period. Identification of these isolates were made based on morphological and cultural characters. The fungal colony of F. verticillioides isolates on PDA were initially white, cottony (Plate 1)which after 7 days of incubation at 28±2ºC developed pigmentation like pink, light purple, dark violet (Ayesha et al., 2020). The mycelia growth was observed 24-48 hours after inoculation on PDA medium in M. phaseolina isolates. Within 6-7 days, the colonies became carbonaceous, fluffy, brown to black in colour (Plate 2) covering the complete plate and numerous sclerotia developed throughout the colony with time. Based on morphological and cultural characters of both the pathogens they were identified as F. verticillioides and M. phaseolina. The morphology of the pathogen was in accordance with the description given for maize stalk rot pathogens by Iqbal et al. (2018); Abhay et al. (2020).

How to cite this article

M. Bhavani, B. Mallaiah, D. Bhadru, M. Prameela and S. Vanisri (2022). Survey on the Status of Post Flowering Stalk Rots in Telangana State. Biological Forum – An International Journal, 14(2a): 178-183.