Papaya (Carica papaya L.) is an important tropical fruit crop that holds significant importance in agriculture, particularly in regions with warm climates. It belongs to the family Caricaceae and has a chromosome number of 18. Due to its quick-growing habit, minimal input requirement, and multipurpose uses, papaya has gained considerable popularity. Also, it is a highly remunerative crop and has a high cost-benefit ratio [1]. Papaya is a tropical fruit that is perfect for growing in kitchen gardens. It is a good source of minerals, potassium, vitamin C, vitamin A, and other vitamins. The crop may bring in a good income for farmers and is generally easy to cultivate and maintain [2]. It has a longer fruiting period. Papaya trees are quickly growing to resemble trees. The fruit has an oval or pear shape. Dioecious papaya plants are distinguished by having distinct male and female blooms that develop on separate plants [3]. For them to produce fruit, insect pollination is crucial. Certain papayas are hermaphrodites, meaning they can self-pollinate by producing both male and female flowers on the same plant. In commercial production, these hermaphrodite papaya varieties are more widely utilized [4].

One of the key components of horticultural production systems worldwide is growing media. It serves as a reservoir for water, minerals, and nutrients; oxygen to permeate the roots; and gaseous exchange between the roots and the surrounding atmosphere. A healthy growing medium gives the plant the support it needs. It is also crucial for the germination of seeds. The growth media's composition affects the quality of the seedlings [5]. The development of papaya required sustainable seeds. The availability of the seeds with the quality and vigorous seedling becomes the priority for papaya nursery growers [6]. The problems faced in growing papaya are because of the long process of germinating seeds if there is no pre-treatment for the seeds and they cannot germinate at the same time, so that causes the seeds to not grow uniformly [7]. The emergence of papaya seeds is generally completed in 2-3 weeks. Papaya seed is enclosed within a gelatinous sarcotesta, which makes for a long process for seed germination. The sarcotesta itself contains phenolic compounds [8].

Papaya is primarily propagated by seed, yet low germination and weak seedling vigor occur from early seed degeneration after harvest [9]. In the pursuit of improving these essential attributes, the application of growth regulators and the selection of appropriate propagation media have gathered significant attention among researchers and horticulturists [10]. Understanding how these variables influence the early stages of papaya growth is pivotal for enhancing the quality and yield of papaya crops and ultimately contributing to the advancement of sustainable agriculture and the production of nutritious fruits [11]. Germination of seeds is also greatly influenced by the propagation medium. Media serve both as a growing environment and a source of nutrients for plant development [12]. Humus soil provides sufficient nutrients to plants and has good water-holding potential. Besides having good water-holding capacity also has sufficient porosity, thus permitting adequate moisture and exchange of gases between the germination growth media and the embryo of the seed [13]. This study, therefore, assessed seed germination and seedling characters in collected accessions of Carica papaya in some southern states of Nigeria.

Source of Planting Materials

Collections of Carica papaya were sourced from open markets across the following southern Nigerian states: Abia, Imo, Rivers, Enugu, and Anambra. Six (6) accessions were collected per state, resulting in 30 accessions. These were collected as mature fruits. The collections were based on morphotypes: oblong, long, round; and pulp color: yellow, red, etc.

Germination and Seedling Growth Studies

The seeds from different accessions, collected as mature fruits, were sown at 20 seeds in a pot; 10 pots were assigned to each accession, making it a total of 300 pots. The following data were taken: days to emergence and number of seedlings that emerged. At 2, 3, 4, 5, and 6 weeks after emergence (WAE), the following data were recorded: seedling height, seedling vigor, number of leaves, seedling girth, leaf length, leaf width, and dry matter.

Seedling Emergence (SE)

Days to 50% Seedling Emergence: The number of days to 50% emergence of the planted seed in different accessions was noted and recorded [14].

Seedling Height and Vigor Index

Seedling height (SH): The height of each seedling from different accessions was measured with a meter rule from ground level to the tip of the seedling 2, 3, 4, 5, and 6 weeks after germination.

Seedling Vigor Index (SVI): This was determined by multiplying seedling height (SH) by seed emergence (SE) [14].

Statistical Procedures

The data collected was subjected to analysis of variance using the GenStat Discovery 12th edition. The analysis estimated the location and genotype effects as well as their interactions.

Days to Emergence, Total Emergence, and Vigor Characteristics in Different Accessions of C. papaya Seeds

Days to emergence, total emergence, and vigor characteristics in different accessions of C. papaya seeds planted in the nursery are presented in Table 1. The results revealed that the days to first emergence of the seedlings emerged between 17 and 24 days after planting. However, accession AN4 had the longest days to first emergence (23). While the shortest (17.0) was recorded in IM1. The mean value of days to first emergence among the accessions under consideration is 21 days, while the LSD (p<0.05) is 3.52. Furthermore, days to 50% emergence ranged from 22 to 35 days. However, accession RV6 had the highest days to 50% first emergence (35.0). While IM2 had the shortest (22.0). The mean value of days to 50% first emergence among the accessions under consideration is 30.5, while the LSD (p < 0.05) is 3.95. The highest value of the total number of emerged seedlings (40.0) was observed in accession IM5. While the lowest value of 31.0 was recorded in EN2. The mean value percentage emergence among the accessions being considered is 34.7, while the LSD (p<0.05) is 4.03 (Table 1).

Moreover, the percentage emergence of the emerged seedlings in different accessions of C. papaya planted in the nursery is presented in Table 1. Also, the highest percentage emergence (80.0%) was observed in accession IM5. While the lowest value of 62.0% was recorded in EN2. The mean value percentage emergence among the accessions being considered is 69.5, while the LSD (p < 0.05) is 8.05. The seedling vigor index in different accessions of C. papaya planted in the nursery is presented in Table 1. The highest values of seedling vigor index (2.7) were observed in accessions AB5 and EN2. While the lowest values of 1.1 were recorded in EN5 and RIV5. The mean value percentage emergence among the accessions being considered is 1.8, while the LSD (p<0.05) is 0.90.

Table 1: Days to Emergence and Vigor Characteristics in Different Accessions of C. papaya Seeds.

Key: ACC- Ascension; LOC- Location; ns- not significant; * = P<0.05; ** = P<0.01; *** = P<0.001

Seedling Characteristics of C. Papaya at 2-6 Weeks after Emergence (WAE)

Seedling Height (SHT) 

The seedlings' height in 30 accessions of C. papaya from 2 to 6 weeks after emergence (WAE) is shown on Table 2. At 2 WAE, the accession IM4 and IM6 had the longest SHT (9.00cm), while accession EN5 had the shortest (3.00 cm). The accession effect was highly significant at p<0.001. At 3 WAE, the best SHT (10.00cm) was recorded in accession IM4 and IM6, while the lowest (4.00 cm) was observed in accession EN5. The accession effect was highly significant at p<0.001. At 4 WAE, the highest SHT (11.00cm) was recorded in accession IM4 and IM6, while the lowest (6.00 cm) was in accession EN5. Very highly significant (p<0.001) of accessions effect was equally observed, Also, at 5 WAE, the longest SHT (12.00cm) was recorded in accession IM6, while the shortest (5.00 cm) was observed in accession EN5. Moreover, at 6 WAE, accession RV1, had the longest   SHT (14.00cm), while the lowest (8.67 cm) was recorded in accession EN5. The accessions effect was also highly significant (p<0.001).

Table 2: Seedling Height (cm) in Different Accessions of C. papaya at 2-6 Weeks after Emergence.

Key: ACC- Ascension; LOC- Location; ns- not significant; * = P<0.05; ** = P<0.01; *** = P<0.001

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