Influence of endophytes on seed quality in heat resilient maize hybrid/RCRMH-2 seed production

Introduction

Crops are colonized by complex microbial communities (Hardoim et al., 2015) [10] , and some of them are detrimental and cause diseases, whereas others promote plant growth and enhance nutrient acquisition and tolerance to biotic and abiotic stresses via a multitude of mechanisms (Brader et al.,) [3] . The fungi or bacteria which grow inside the plant tissue without causing any harm to the host are termed as endophytes. Endophytes are endosymbionts that are integral components of a plant micro-ecosystem, which is associated with the plant throughout its life cycle without inducing any disease. They perform symbiotic functions, including production of secondary metabolites or synthesis of signalling molecules that function as both internal and external stimuli during mutualistic interactions (Tidke et al., 2018) [19] . Endophytes produces various plant growth hormones viz., auxin, abscisic acid, ethylene, GA 3 , IAA, enzymes and biologically active metabolites which help augment the host betterment. Maize is the only food cereal that can be grown in diverse seasons, ecologies and uses, because of potential market and lower risk involved in the production. To meet the demand of the seed requirement the private and public sectors have introduced their hybrids. As a public sector organization, the University of Agricultural Sciences, Raichur has developed maize hybrid (RCRMH-2) and released it for general cultivation in Karnataka. RCRMH-2 is heat stress resilient hybrid and multiple disease resistant. Recent studies predicted that world population may reach 8.6 billion by 2030 (www. India budget. gov.in) such an increasing human population places pressure on agriculture. There is a need to always meet the increasing demand. To feed this population with quality and to run industries, an increase in production is needed. On the other side, today's agriculture is becoming input-intensive with more reliance on synthetic fertilizers and agrochemicals to fulfill the feed demand of the growing numbers. (Lin et al., 2019) [13] . In this scenario, the use of beneficial endophytic microbes as an enchanting strategy to overcome the use of synthetic and chemical products.

The present study aims to explore the potential ability of a few selected endophytic fungi in modulating seed quality parameters under laboratory conditions. The reason behind the use of endophytes is to maintain a safe environment. These are the promising agents that promote their host growth even in stressed environments. Today these endophytic bacteria grab the attention, because these are the potential source of sustainable agriculture (Fiore et al.,1995) [7] and prevents the growing population of the world from future hazards in agriculture.

Materials and Methods

Collection of experimental materials

The freshly harvested maize hybrid RCRMH-2 seeds produced during rabi season to evaluate the effect of endophytes on seed yield and its parameters (Pallavi et al., 2025) were used in this experiment as seed source to evaluate the seed quality parameters.

Laboratory experiment

The laboratory experiment was carried out with 12 treatments replicated four in a Factorial Complete Randomized Design (FCRD) during rabi season of 2024-25 at the Department of Seed Science and Technology, College of Agriculture, Raichur, Karnataka. The first factor Endophytes (P) viz., Beauveria bassiana at 5% (P 1 ), Metarhizium anisopliae at 5% (P 2 ), Bacillus subtilisat 8% (P 3 ) and second factor consists methods of application (M) viz., M 1: Seed treatment 20 g kg -1 of seed, M 2: Seed priming for 12 hrs duration with a solution ratio of 1:1, M 3: Foliar spray at 30 and 45 days and M 4: drenching at 30 and 45 days.

One hundred seeds in four replications were drawn at random from each treatment, and the germination test was conducted using the between paper (BP) method as per ISTA (Anon., 2024). The rolled towels were incubated in a germination chamber maintained at 25 + 2°C temperature and 90 + 5 per cent relative humidity. The germinated Seedlings were evaluated on the seventh day at the final count and seed germination was expressed based on normal Seedlings.

During the final count, ten normal seedlings will be selected at random from each treatment andreplication. The seedling length was measured from the tip of the longest root and growing meristematic tip of shoot and expressed in centimeter.

Ten seedlings used for measuring the shoot and root length were kept in butter paper covers and dried in a hot air oven at 70 °C + 2°C for 24 hours. Then the butter paper bags were removed and cooled in desiccators for 30 minutes and weighed on an electronic balance and expressed in grams.

Seedling Vigour Index

Seedling vigour index was calculated as per the formula given by Abdul Baki and Anderson (1973) [1] expressed as a whole number.

Seedling vigour index-II = Germination (%) x Mean seedling dry weight (g).

Statistical analysis

The data obtained from the experiment were statistically analysed by adopting appropriate statistical methods as outlined by Panse and Sukhatme (1985) [16] . The critical difference (CD) values were calculated and treatments means were compared at 1 per cent for laboratory observation.

Results and Discussion

The results pertaining to seed quality parameters viz., germination percentage, seedling length, seedling dry weight, seedling vigour index-I, seedling vigour index-II of the maize hybrid (RCRMH-2) were found to be significant due to the effect of endophytes and its application methods (Table 1). Among the different treatments imposed application of Metarhizium anisopliae via as seed treatment (P 2 M 1 ) recorded significantly highest germination percentage (99.50%), seedling length (30.86 cm), seedling dry weight (2.54 g), seedling vigour index-I (3071), seedling vigour index-II (252), followed by Metarhizium anisopliae applied as priming (P 2 M 2 ). The probable reason may be seed treatment with beneficial endophytes during the parental plant's life cycle results in vertical transmission of these microbes to the next generation of seeds, leading to significantly enhanced seed quality parameters. Where the endophytes effectively colonize the reproductive tissues (flowers, ovules, pollen) of the parent plant and are passed directly into the developing seeds. This ensures that the next generation of seedlings is immediately inoculated with beneficial microbes upon germination, by these endophytes produce phytohormones (like auxins and gibberellins) and enzymes (like 𝛼 -amylase) that promote cell division, elongation, and the breakdown of stored nutrients, providing the seedling with a strong start. giving them a significant competitive advantage from the earliest stages of life (Maiwenn and Robin., 2021). In contrast Bacillus subtilis applied as foliar spray (P 3 M 3 ) recorded minimum germination percentage (89.00%), seedling length (19.07 cm), seedling dry weight (1.97 g), seedling vigour index-I (1697), seedling vigour index-II (175). So taken together, these effects make Metarhizium anisopliae an effective, eco-friendly seed treatment that boosts seed quality sustainably. (Rivas-Franco et al., 2020) [17] . Similar result found by Lastochkina et al., 2020 [12] in wheat, Espinoza et al., 2019 [6] in chilli, Gayathri et al., 2020 [8] in maize, Chowdhury et al., 2024 [4] in wheat, Elena et al., 2011 [5] in tomato, Theertha et al., 2023 [18] in cowpea.

Conclusion

Based on experimental results, it was concluded that application of 20 g /kg Metarhizium anisopliae via as seed treatment recorded higher seed quality attributing parameters of hybrid maize. The results affirm that endophytes enhances seed early seedling establishment through improved phytohormone activity, nutrient mobilisation so that seed producers may get good quality seeds than other treatments. It can be recommended as a practical, eco-friendly technology for augmenting productivity and sustainability in seed production.

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