Enhancement of Seed Germination and Seedling Vigour through Different Seed Priming Treatments in Blackgram (Vigna mungo L.)

India is the largest producer and consumer of pulses in the world. Pulse crops are an important part of Indian agriculture and have almost three times as much high-quality protein per gram as cereals (Upadhayay et al., 2006). Blackgram (Vigna mungo L.), one of the world’s most nutrient-dense pulse crops, is grown in India and is a member of the leguminoseae family with chromosome number 2n = 2 × = 22 (Malik, 1994). About 70% of the world’s Blackgram still originates in India, despite the fact that Indian immigrants introduced it to other tropical areas (Dahanayake et al., 2014). Blackgram is India’s third-largest pulse crop, accounting for 16 per cent of the country’s total pulse area and 9 percent of total pulse production and contributes significantly to sustainable agriculture by enriching the soil via biological nitrogen fixation. It is mostly grown during the rainy season in Madhya Pradesh, Maharashtra, Tamil Nadu, Uttar Pradesh, Rajasthan and Gujarat and during the winter (rabi) season in Andhra Pradesh and West Bengal (Ram et al., 2010). Due to its short duration, photosensitivity and dense crop canopy, it plays a critical role in crop intensification, diversity, conservation of natural resources and system sustainability (Katiyar and Dixit, 2010). This crop has poor germination and establishment because it is grown in rain-fed marginal lands with insufficient nutrients. Low-fertility soils make it hard to get good germination, which is important for getting a good crop yield (Joshi et al., 2013). High and stable production requires quality seed. Seed quality is the basis of efficient crop production and farmers need such seeds for optimum yield production. Therefore, various procedures are applied in seed production technology that aims to improve not only the germination of seeds but also the speed of its germination (Miladinov et al., 2021). Seed priming is administered as a pre-sowing treatment to help plants endure these issues and the unfavorable weather circumstances.
       
Pre-sowing treatment known as priming involves partially hydrating seeds such that germination begins but no visible radical emergence is seen (Giri and Schillinger, 2003). Using primed seeds has been shown to increase germination rate, germination uniformity, rapid growth, early blooming and yield. As reported, seed priming is a crucial development for speeding up and uniformly emerging of seeds, as well as enhancing resistance for adverse environment conditions in seeds (Heydecker et al., 1973; Harris et al., 1999). Singh et al., (2015) found that organic solutes such proline accumulation in primed seeds increased tolerance to salinity by increasing K⁺ and Ca²⁺ accumulation while decreasing Na⁺ accumulation. There are numerous priming techniques available to improve seed germination. Osmotic priming agents include sugar, polyethylene glycol (PEG), glycerol, mannitol, sorbitol and specialty vermiculite compounds (Pawar and Laware, 2018). Osmo-priming strengthens the antioxidant system and increases seed germination potential, resulting in an increased stress tolerance in germinating seeds (Tiwari and Agarwal, 2021). After drying, organic priming plant extracts such as neem leaf extract, curi leaf extract, tulsi leaf extract and neem seed kernel powder for maize may be used. Priming of seeds with different concentrations of organic treatments are being adapted for improving the physiological stamina of the seed, achieving uniform crop stand and further improving quality of seed by minimizing the variation of seed quality within the seed lots (Sajjan et al., 2017). Over an extended period of time, it was discovered that a larger concentration of this powder was advantageous (Sharma, 1995).

The experiment was done in the postgraduate Seed Testing Laboratory, Department of GPB, SHUATS, Prayagraj (Uttar Pradesh). Priming treatments were applied at varying concentrations with Blackgram (var. PU-31), viz;- T₀-Un-primed (Control), T₁- DH₂O, T₂- PEG₆₀₀₀@ 20%, T₃- NaCl@ 1%, T₄- CaCl₂@ 1%, T₅- Tulsi Leaf Extract@ 5% and T₆-Curi Leaf Extract@ 5%. Afterwards, the seeds were placed in their respective priming solutions and allowed too steep for twelve hours. Before being used for planting, the seeds were air dried in the shade at 20°C for 24 hours to restore their natural moisture content.
 
Preparation of solutions
 
The solution was obtained by putting one gram of each ingredient. These chemicals were added to 1000 ml distilled water, continually stirring. When the solution volume reaches one litter, it should be a 1000 parts per million stock solutions of each component. To avoid contamination, the chemical flasks were covered with muslin cloth. The PEG₆₀₀₀ solution 20% was made by taking 200 (g.) of PEG and diluting it with distilled water to a volume of 1000 ml. finally, NaCl (1%) solution 10 (g.), CaCl₂ (1%) solution 10 (g.), Tulsi leaf extract (5%) solution 50 (g.) and Curi leaf extract (5%) solution 50 (g.) were also taken in the same way.
 
Preparation of plant leaf extract
 
Drying the tulsi and curi leaves in the shade was the first step in preparing the plant leaf extract. A mortar and pestle were used to grind the shade-dried leaves into a fine powder. Afterwards, weigh 50 grams of leaf powder and dissolve it in 1000 ml of pure water that has been calibrated in the beakerto generate a 5 percent leaf extract. The leaf extract was filtered through muslin cloth in order to remove any unwanted particles or leaf debris.
 
Moisture content after priming
 
 

The following characteristics were observed: germination percentage (ISTA, 2004), root length (cm), shoot length (cm), seedling length (cm) (ISTA, 2004), seedling fresh weight (g), seedling dry weight (g) (ISTA, 2004), seedling vigour index-I and seedling vigour index-II (Baki and Anderson, 1973). The collected experimental data were analyzed statistically to determine the analysis of variance, range, mean, critical difference and coefficient of variation (Fisher, 1936).

The results indicate that the treatments had an impact on all of the characteristics tested, with a significant difference between the control (unprimed seeds) and the primed seed (Table 1 and Fig 1 to Fig 6).
 

 

 

 

 

 

 

       
All seedling characteristics, including the percentage of seedlings that germinate, Root length (cm), shoot length (cm), seedling length (cm), seedling fresh weight (g.), seedling dry weight (g.), Seedling Vigour index-I and Seedling Vigour index-II were profoundly influenced by PEG₆₀₀₀@ 20%.
       
Significantly highest germination percentage (86.25%) recorded in seed treatment with T₂-PEG₆₀₀₀@20% followed by T₄- CaCl₂@ 1% (82.75%), which was at par with T₆-Curi leaf extract@ 5% (82.75%) and found to be lowest in T₀-Control (78.75%). Fig 1 depicts the germination percentage data and similar findings are reported by Heydecker et al., (1973); Arif et al., (2014); Arun et al., (2017) and Nawaz et al., (2013). The increase in germination % under primed seed might be a result of water and certain substances accelerating metabolic activities, resulting in fast cell division and multiplication. Numerous osmotic agents, such as PEG, have been found to improve germination capacity (Toklu et al., 2015), which is essential for the seed embryo’s growth and development.
       
Maximum root length, shoot length and seedling length were measured in seed treatment with T₂-PEG₆₀₀₀@ 20% (17.10 cm, 21.40 cm and 38.50 cm), followed by T₄- CaCl₂@ 1% (15.45 cm, 19.65 cm and 35.10 cm), which was at par with T₆-Curi leaf extract@ 5% (14.25 cm, 18.87 cm and 33.12 cm) and found to be minimum in T₀-Control (10.55 cm, 13.20 cm and 23.75 cm), respectively. Fig  2 depicts the length of root shoot and seedling data and similar findings are reported by Bray et al., (1989); Saha et al., (1990); Heydecker et al., (1973); Afzal et al., (2008); Ananthi et al., (2015) and Babu and Rosaiah,(2017). The increased seedling length seen with PEG and halo-priming is a result of the cumulative positive effect of H₂O and PEG on root and shoot growth (Demir and Oztokar, 2003). According to some research, seed hydration equivalent to, but not higher than, the lag phase of priming enables early DNA replication, enhanced RNA and protein synthesis, increased ATP availability, quicker embryo development and repair of degraded seed components (Karssen et al., 1989). All of these factors contributed to an increase in seed root and branch length, which resulted in an increase in overall seedling length.
       
Seedling fresh weight and dry weight recorded maximum in seed treatment with T₂-PEG₆₀₀₀@ 20% (4.27 g. and 0.448 g.), followed by T₄- CaCl₂@ 1% (3.97 g. and 0.417 g.) which was at par with T₆-Curi leaf extract@ 5% (3.77 g. and 0.380 g.) and found to be minimum in T₀-Control (1.80 g. and 0.250 g.), respectively. Fig 3 and 4 depicts the seedling fresh and dry weight data and similar findings are reported by Bewley and Black, (1994); Koehler et al., (1997); Sedghi et al., (2010); Arif et al., (2014) and Babu and Rosaiah, (2017). Ashrsaf and Rauf, (2001) also revealed that their findings on root and shoot fresh weights are consistent with those of who observed that the fresh and dry weights of seedlings from halo-primed seeds were significantly greater than those from other un-primed seeds. Jie et al., (2002) demonstrated that PEG treatment activates numerous chemicals that enhance germination, resulting in increased root and shoot dry matter accumulation.
       
Seedling vigour index-I and II was recorded highest in seed treatment with T₂-PEG₆₀₀₀@20% (3318.62 and 38.64), followed by T₄- CaCl₂@ 1% (2980.60 and 35.49), which was at par with T₆-Curi leaf extract@ 5% (2740.00 and 31.42) and found to be lowest in T₀-Control (1870.50 and 19.72), respectively. Fig 5 and 6 depicts the seedling vigour index-I and II data and similar findings are reported by Finch-Savage et al., (2016); Sedghi et al., (2010); Toklu et al., (2015); Arif et al., (2014); Saha et al., (1990); Paparella et al., (2015); Musa et al., (1999) and Hussian et al., (2014). The increased seed vigour index-I under PEG and CaCl₂ treatment compared to control is attributable to their pro-germination and seedling length promoting actions. During osmotic priming, the normal/low-vigor seed’s vigour may be boosted due to the mobilization of food reserves and the activation and re-synthesis of certain enzymes. It has been found that primed seeds exhibit a more favorable germination pattern and a greater degree of vigour than un-primed seeds (Ruan et al., 2002).
 
Outlook
 
This research has helped us in the screening of priming strategies for seed germination and seedling characteristics at 12 hours. The outcomes of this study can be used to further research.
► The study focused on improving the quality of black-gram seeds by different priming treatments in terms of germination, seedling characteristics and vigour indices.
► The study looked at how different priming treatments could improve the quality of black-gram seeds, such as how quickly they sprouted, how well they grew and how strong they were.
► Seeds exhibited poor dormancy or may have exhibited late germination as a result of deterioration during harvesting, processing and storage. Seeds are treated with various priming methods (strategies) before to germination to reduce the degradation impact and improve seed quality.
► Seed treatment with T₂-PEG₆₀₀₀@ 20% showed maximum germination percentage, seedling length (cm), weight of seedling (g.) and vigour indices among all the treatments, due to their positive effect and less phyto-toxics.
► The greater percentage emergence of seedlings and vigour indices that were observed with PEG in comparison to other treatments suggest that it should be used as a pre-sowing treatment to retain more elevated seed vigour.

Priming improves the germination and vigour of blackgram seeds. Osmo-priming (PEG) and Halo-priming (CaCl₂) greatly improved black-gram germination and seedling characteristics. Osmo-priming with PEG resulted in the greatest increase in viability and vigour, as well as the greatest rise in germination. Priming the black-gram seeds for 12 hours with PEG results in improved germination, vigour and seedling characteristics. These findings are the outcome of a six-month investigation; consequently, further research is required to make valid suggestions.

None.