The Evaluation of the Fruit Morphological Diversity in Some Species of Pepper (Capsicum ssp.)

Abstract

Introduction To specify the diversity of pepper plant (Capsicum ssp.) population and the inheritance of fruit characteristics for use in seed production breeding programs, there is a need for a diverse population in terms of the characteristics affecting fruit yield. By a large variety of options available for each product, there is a greater probability of selecting the best decision. A population's genetic variety may be used in several ways, including selection and hybridization. Pepper is a plant belonging to the genus Capsicum and the family Solanaceae. It is cultivated globally, particularly in tropical and subtropical regions. The genus Capsicum contains more than 30 wild and domestic species, which are classified according to flower structure, fruit, and the number of chromosomes (2n= 24, 26). Materials and Methods To compare different pepper species based on fruit morphology, a greenhouse experiment was conducted under hydroponic conditions in Zarandieh region, Markazi province, in a completely randomized design with three repetitions in 2021. The seeds of 42 pepper genotypes from 7 species were obtained from Gene Bank of Leibniz Institute of Plant Genetics and Crop Plant Research (IPK). Initially, the seeds were sown in dedicated planting trays. Once the seedlings had grown six leaves, they were transplanted to the main greenhouse. Within the greenhouse, the rows of cultivation were spaced 160 cm apart, with a 25 cm gap between individual plants. Each genotype was represented by ten plants. Throughout the growing season, the plants were managed by maintaining two branches and removing any surplus ones. In this research, the following characteristics were evaluated: fruit production across three harvests, fruit weight, fruit length and diameter, fruit flesh thickness, fruit flavor (spicy or sweet), unripe fruit color, and ripe fruit color. Descriptive statistics of evaluated trait, including mean, minimum and maximum traits and the percentage of phenotypic and genotypic diversity coefficients, heritability, and the analysis of variance and comparison of means, were used to analyze the data. Results and Discussion A diverse collection of pepper was evaluated due to the fruit morphological traits and significant differences among different genotypes in terms of these traits. The average fruit weight of the assessed population was 26.54 g. The minimum and maximum fruit weights of 152.70 and 0.13 g were related to genotypes 409 and 276, respectively. Genotype 318, with an average weight of 144.20 g, was not significantly different from genotype 409. Both genotypes were of the species annuum, but were in two separate groups regarding fruit morphology. The heritability rate of fruit weight was 93%, which is consistent with the results of Usman et al. (2014). Length, diameter and length to diameter ratio (fruit morphology index) are the most important factors in marketing pepper fruit. The mean fruit length, diameter and morphology index were 6.35, 2.57 cm and 3.04, respectively. The highest fruit length was related to genotypes 296 and 318 at 26.33, 20.20 and 19 cm, while the lowest fruit length was 0.70, related to genotype 277. The genotypes with the highest lengths were long pepper and Kapia sweet pepper, respectively, and the genotypes with the shortest lengths tasted spicy. Genotypes 409, 200, 318, 326, 272 and 348 had the largest diameter with 6.50, 6.23, 5.80, 5.67, 5.60 and 5.30 cm, respectively. These genotypes are bell, round, Kapia, triangular, triangular, round and sweet in terms of morphology. The smallest fruit diameter belonged to genotype 293 (0.30 cm), and the nineteen genotypes with a diameter of less than 2 cm did not differ significantly from 293. Twenty genotypes with the smallest fruit diameter have a pungent flavor (Table 1). The range of the fruit morphology index was from 0.56 to 8.99. The lowest and highest values were associated with genotypes 342 and 296, respectively (Table 3). The fruit of genotype 296 was sweet, whereas the fruit of genotype 342 was spicy. The heritability of length, diameter and fruit morphology index were 0.97, 0.97 and 0.98%, respectively. The lowest and highest numbers of fruits per plant in each hand-harvest were 1 and 67 fruits, respectively, belonging to genotypes 342 and 326. However, regarding shallow length, diameter, pulp thickness and, consequently, the low weight of the fruit in genotype 342, an almost low yield of this genotype was obtained in three harvests (2742.67 kg/ha). In contrast, genotype 318, despite its small number of fruits per hand-harvest (3 fruits per hand-harvest), had the highest fruit yield of 25379.20 kg Per hectare due to having fruits with large size and pulp thickness and as a result of high fruit weight. The lowest yields related to genotypes 276 and 293 belonged to C. frutescens L., with fruit yields of 17.60 and 44.00 kg/ha in three harvests. However, there was no statistically significant difference among the performance of these genotypes and the genotypes 277, 210, 282, 358, 261, 332, 394, 304, 311, 407, 321, 215, 427, 203, 342 and 200. The percentage of phenotypic and genetic variations in fruit yield was 61, 55% and the heritability of fruit yield was 81%. Conclusion This study evaluated a diverse collection of different species of pepper with a wide range of appearance traits. However, the most desirable and marketable characteristics of the fruit were obtained from genotypes belonging to C. annuum. However, genotypes belonging to other species, which were not addressed due to the high number of fruits per plant and resistance to pests and diseases, can play a complementary role in hybrid seed production breeding programs. Based on the results, genotypes 318 (Kapia, yellow and sweet), 287 (long, red and spicy), 348 (round, red and sweet), 272 (triangular, red and sweet), 309 (black, red and sweet) and 296 (long, red and sweet) could be introduced as cultivars after evaluating their compatibility, in terms of their high yield, suitable size fruits and marketability. In addition, because to the substantial variety of the examined population, breeding efforts might develop hybrid cultivars with unique traits.

Keywords

• broadscence heritability
• fruit yield
• morphological diversity
• pepper germplasm