Finger millet (Eleusine coracana), also known as ragi, is a climate-resilient, gluten-free cereal crop widely cultivated in Africa and Asia, particularly in India. It is an allotetraploid species (2n = 4x = 36) valued for its rich nutritional profile, including high levels of calcium, iron, dietary fiber and essential amino acids (Kudapa et al., 2023; Maharajan et al., 2024). Due to its adaptability and health benefits, finger millet plays a vital role in food and nutritional security, especially in semi-arid regions (Nagaraja et al., 2025). However, despite its resilience, the crop is vulnerable to several fungal pathogens, among which Rhizoctonia solani has emerged as a significant threat.

Rhizoctonia solani is a soil-borne, necrotrophic fungus that causes various plant diseases such as sheath blight, seedling blight, root rot and damping-off. First described in 1815 by De Candolle and later taxonomically expanded by Kühn, its sexual (teleomorphic) stage is classified as Thanatephorus cucumeris (Ogoshi et al., 1996). In finger millet, the pathogen causes sheath and banded blight, producing lesions and characteristic banding on leaf sheaths, first reported in Karnataka. The pathogen is grouped into several anastomosis groups (AGs), with AG1-IA being the most virulent in finger millet (Carling et al., 2002). Its morphological features include right-angled branched septate hyphae, dull white to brown mycelium and sclerotia formation.

Considering the increasing incidence and detrimental impact of Rhizoctonia solani on finger millet productivity, it is essential to evaluate the performance of available genotypes under disease stress conditions. Therefore, the present investigation was undertaken to assess the performance of finger millet [Eleusine coracana (L.) Gaertn.] genotypes under both normal and Rhizoctonia-infected conditions in a polyhouse environment. The study aimed to evaluate disease response, estimate genetic variability and analyze the relationship among yield and its contributing traits through correlation and path coefficient analysis. The results of this study will help in identifying potential resistant genotypes and provide valuable information for the development of high-yielding and stable finger millet varieties under biotic stress conditions.

The experimental material consisted of 35 finger millet [Eleusine coracana (L.) Gaertn] genotypes collected from the Indian Institute of Millets Research (IIMR), Hyderabad and M.S. Swaminathan Research Foundation (MSSRF), Jeypore, Odisha. The genotypes represented both improved varieties and indigenous landraces. The study was conducted during the Rabi season of 2024 in a polyhouse at the M.S. Swaminathan School of Agriculture (MSSSoA), Centurion University of Technology and Management (CUTM), under controlled environmental conditions. A completely randomized design (CRD) was adopted with three replications and two seedlings per pot were maintained for both healthy and diseased treatments. Seeds were initially sown in nursery trays on December 18, 2024 and transplanted into pots on January 12, 2025.

Observations were recorded on 14 quantitative traits including days to 50% flowering, days to maturity, plant height at maturity, flag leaf blade width and length, peduncle length, ear head length, number of tillers and productive tillers per plant, number of fingers on the main ear, 1000 grain weight, grain yield per plant, harvest index and per cent disease index (PDI). Disease severity was rated using a 0-5 scale and PDI was calculated using the formula:
 

 

Genotypic and phenotypic correlation coefficients were computed following Falconer (1981). Between October and December 2023, surveys were conducted in four districts of Odisha Paralakhemundi, R. Udayagiri, Gajapati and Ganjam for collection of diseased samples. Five isolates of Rhizoctonia solani were obtained from infected rice and finger millet plants using sequential sterilization and cultured on potato dextrose agar (PDA) at 25±2°C. Pathogenicity was confirmed by detached leaf assay and in vivo pot inoculation using mycelial suspension. The cultural variability of the pathogen was examined on different media (PDA, V8, czapek dox, oat meal and dextrose agar) and growth was monitored under varied pH conditions (4.5, 5.5, 7.0 and 8.0). Seed mortality tests were conducted to assess infection levels by placing seeds around a central mycelial disc on PDA and recording mortality over a 144-hour period. The evaluated genotypes were VL 376, IIMR 7028 FM, FM PR 1731, VL 408, FM WN 566, KOPN 1055, VR 1174, VR 1194, VL 410 FM, VR 1238 FM, VR 1223, VR 1192, IIMR 7202, VR 1184, BR 14 28, FM 1213, VR 1200, VR 1152, IIMR 7066, KMR 1151, Taya, Madli Muskuri, Lalsuru Mandia, Bada Kumnda, Badatara Dangardli, Bada Mandia, Bagadadli, Telugu Mandia, Chillika , Lala Mami Mandia, KMR 301.

Analysis of variance revealed highly significant differences among the 35 finger millet genotypes for most of the traits studied (Table 1). The mean sum of squares due to genotypes was highly significant (p<0.01) for traits such as days to 50% flowering, plant height, days to maturity, grain yield per plant and other yield-contributing characters. This indicates the presence of substantial genetic variability among the genotypes evaluated. Higher magnitudes of genotypic mean squares were observed for plant height, days to maturity and grain yield per plant, suggesting differential genotypic responses. The relatively low error mean squares for most traits indicate good experimental precision and reliability of the recorded observations.



Further, the ANOVA indicated significant differences among genotypes for all the characters studied, except percent disease index, which was significant at the 5% level (p<0.05) (Table 1). For instance, days to 50% flowering recorded a mean square value of 5.105 compared to an error variance of 0.54, confirming the existence of significant variation among genotypes.

Correlation analysis under controlled conditions revealed that grain yield per plant exhibited significant positive correlations with peduncle length (0.477**), number of productive tillers per plant (0.602**), thousand grain weight (0.419*) and days to maturity (0.417*). Plant height (0.240) and number of fingers per ear (0.243) also showed positive but non-significant associations with grain yield.

Days to 50% flowering showed a strong negative association with grain yield per plant (-0.559) and peduncle length (-0.444), indicating the advantage of early flowering genotypes for yield improvement. Flag leaf blade length showed a positive correlation with number of fingers per ear (0.461*) and plant height (0.283), while a significant negative correlation was observed with number of productive tillers per plant (-0.505**). Ear head length was strongly and negatively correlated with number of fingers per ear (-0.704**). The number of tillers per plant (0.191) and harvest index (0.036) exhibited weak but positive associations with grain yield.

Correlation analysis under disease stress conditions (Table 2) indicated that grain yield per plant had significant positive correlations with plant height (0.457**), harvest index (0.511**) and thousand grain weight (0.352*). Peduncle length (0.296), ear head length (0.279) and number of tillers per plant (0.313) also showed positive but non-significant associations with yield.



Days to 50% flowering exhibited a significant negative correlation with grain yield (-0.559**), suggesting that early flowering genotypes may perform better under Rhizoctonia solani stress. Per cent disease index (PDI) was significantly and negatively correlated with grain yield (-0.416*), indicating the adverse effect of disease severity on productivity. Flag leaf blade length (-0.001) and flag leaf blade width (-0.235) showed negligible negative associations with yield. Similarly, number of productive tillers per plant (-0.179), number of fingers per ear (-0.118) and days to maturity (-0.009) exhibited weak negative correlations with grain yield.

Path coefficient analysis under controlled conditions indicated that peduncle length (0.340), number of productive tillers per plant (0.497), number of fingers per ear (0.411), plant height (0.214), harvest index (0.143) and days to maturity (0.464) exerted positive direct effects on grain yield per plant. Among these traits, peduncle length and number of productive tillers per plant also showed strong positive correlations with grain yield.

Negative direct effects were observed for days to 50% flowering (-0.233), flag leaf blade length (-0.083), ear head length (-0.032) and number of tillers per plant (-0.153). Thousand grain weight exhibited a negative direct effect (-0.168), but it maintained a positive correlation with yield due to strong indirect effects through plant height and number of tillers per plant.

Under Rhizoctonia solani stress conditions (Table 3), harvest index (0.4075), plant height (0.4337) and thousand grain weight (0.1675) exhibited strong positive direct effects on grain yield per plant. In contrast, days to 50% flowering showed a maximum negative direct effect (-0.3820) on yield. However, percent disease index (-0.416*) and days to 50% flowering (-0.559**) were significantly negatively correlated with yield. Peduncle length (0.296) and ear head length (0.279) showed moderate positive associations with grain yield.

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The present study also evaluated the cultural characteristics of Rhizoctonia solani isolates obtained from infected finger millet genotypes. Among the four culture media tested, potato dextrose agar (PDA) supported the highest radial mycelial growth of 8.90 cm after 120 hours of incubation, followed by V8 agar (8.83 cm), oat meal agar (8.40 cm) and czapek dox agar (7.80 cm).

Mycelial growth on PDA appeared dense, cottony white with smooth margins, indicating active hyphal development. These results suggest that PDA provides optimal nutrient and moisture conditions for the growth of R. solani.

The growth of Rhizoctonia solani varied significantly across different pH levels under laboratory conditions. Maximum radial growth was observed at pH 7.0, with a colony diameter of 8.40 cm after 120 hours of incubation, followed by pH 6.0 (7.70 cm). Moderate growth occurred at slightly alkaline conditions (pH 8.0), while growth declined under acidic conditions. The lowest growth was recorded at pH 4.0 (2.20 cm). These findings indicate that R. solani prefers near-neutral pH conditions for optimal growth.

Seed mortality tests revealed considerable variation in host response among finger millet genotypes infected with R. solani. The genotypes Bada Kumunda and FM1213 recorded the highest seedling mortality (approximately 60%), followed by VR1152, indicating high susceptibility.

In contrast, several genotypes showed lower mortality levels, indicating moderate to high resistance against the pathogen. This variability suggests the presence of genetic differences in disease response among genotypes, which can be utilized in breeding programs aimed at developing resistant cultivars (Table 4).

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Finger millet yield under normal conditions was strongly influenced by productive tillers, 1000-grain weight, panicle length and maturity duration, as also noted by Reddy et al., (2021). Plant height and number of fingers had minor indirect effects (Sneha et al., 2019, Reddy et al., 2013). Early flowering improved yield by avoiding longer vegetative duration. Peduncle length contributed marginally, while longer ear heads and heavier grains enhanced productivity.
Under Rhizoctonia solani stress, yield was mainly governed by harvest index, plant height and grain weight (Subrahmanyam et al., 2000; Amarnath et al., 2018). Early flowering genotypes performed better by escaping peak disease pressure (Chavan et al., 2020), while higher PDI reduced yield, confirming the need for resistance breeding (Mishra et al., 2017). Peduncle and ear head length had positive but limited roles (Kadam et al., 2009), while excessive tillering and flag leaf traits contributed little.

Path analysis showed strong direct effects of peduncle length and productive tillers, while 1000-grain weight, though having negative direct effect, indirectly improved yield via plant height and tillering. These results align with Subrahmanyam et al., (2000); Priyadharshini et al., (2011); Owere et al., (2015) and Gohel et al., (2018), who emphasized peduncle length, productive tillers and balanced maturity traits.

Cultural studies confirmed PDA as the best medium for R. solani growth (Kumar et al., 2014), with V8 and Oat Meal Agar as alternatives. Growth was highest at neutral pH (7.0), in line with Muhsin et al., (2013) and Nuri et al., (2021). Pathogenicity tests identified FM1213 and Bada Kumunda as susceptible checks, while resistant and moderately resistant lines offered breeding potential.

Overall, breeding for early flowering (Chavan et al., 2020), higher harvest index (Subrahmanyam et al., 2000), ideal plant height (Amarnath et al., 2018), larger grains and disease resistance is essential for yield stability under Eastern India conditions.

The results showed considerable genetic diversity among the 35 genotypes of finger millet with remarkable variations in agronomic characters. Isolation and characterization of Rhizoctonia solani from infected leaf and sheath tissues showed varied virulence between isolates. The most favourable medium for growth of fungi was PDA and pH 7.0 was the best for mycelial growth. Pathogenicity tests also verified that the FM1213, Bada Kumunda and VR1152 genotypes were highly susceptible, while many others were moderately to highly resistant. Harvest index (%), plant height (cm) and panicle length (cm) were strongly positively correlated with grain yield (g), thus being good candidates for selection in breeding projects. Early flowering had a positive correlation with grain yield, indicating that early-maturing genotypes are preferable under disease stress conditions. The research highlights the need to use early maturing, high-yielding and disease-resistant genotypes to fight the emerging diseases such as banded and sheath blight of finger millet. These results are useful for breeders and pathologists in creating disease-resistant cultivars appropriate for the Eastern Ghats region and other comparable agro-climatic regions.

All authors declared that there is no conflict of interest.