Morphometry, viability and germination of seeds of Benincasa hispida [(Thunb.) Cogn.]

Abstract

The objective of the study was to evaluate the morphometry, viability and germination of B. hispida seeds, at the Universidad de Córdoba, Colombia. Eight biometric characteristics were measured in a sample of seeds taken at random from a balanced compound originating from 50 fruits. The external and internal morphological description was made on a sample of 10 seeds. Seed viability was estimated by the tetrazolium test, using the combination of two staining times (2 and 3 hours) and three concentrations of (0.5, 1.0 and 1.5%), under a design completely randomized, with six treatments and four repetitions of 50 seeds. The germination test (PRUGER) was performed in a mesh house with four repetitions of 50 seeds to estimate eight physiological parameters of germination. The morpho-metric characteristics of thickness, length and width of seeds showed reduced phenotypic variation, compared with the weight, density and volume of a seed, with variation coefficients greater than 11.7%. The seed, ovoid and flattened, presents an embryo with its cotyledons wrapped in a protective membrane. The viability, determined with tetrazolium, was 89.5-96.5%, while the PRUGER was 100%, with no statistical differences between them (P≥0.05). The combination of 0.5% tetrazolium with 2 hours is sufficient to determine the viability of the seed. Germination elapsed from 6 to 19 days after sowing, with a germination speed index of 0.22, average daily germination of 5.26%, peak value of 5.33 and germination value of 28. Additional key words: winter gourd; biometric characteristics; tetrazolium test; physiological quality. 1 Universidad de Córdoba, Monteria (Colombia). ORCID Espitia-Camacho, M.: 0000-0001-7382-9643; ORCID Villalba-Soto, A. 0000-0003-0558-0801; ORCID Araméndiz-Tatis, H.: 0000-0002-2585-6273; ORCID Cardona-Ayala, C.E.: 0000-0002-9607-3858 2 Corresponding author. [email protected] Doi: https://doi.org/10.17584/rcch.2021v15i1.11724 REVISTA COLOMBIANA DE CIENCIAS HORTÍCOLAS Vol. 15 No. 1, e11724, January-April 2021 e-ISSN: 2422-3719 · ISSN-L: 2011-2173 Benincasa hispida, known as Chinese cucumber, is a cucurbitaceae grown mainly in South and East Asia, where it grows as a climbing or creeping plant, with hairy stems, triangular leaves in alternate arrangement, and small forked strands (Mandana et al., 2012; Ekeke et al., 2019). Benincasa is a monotypic genus with a single cultivated species [Benincasa hispida (Thunb.) Cogn, 2n = 2x = 24] (Pradhan et al., 2020). The importance of the species is given by its cultural and collective value in food, nutrition, biomedicine, traditional medicine and pharmacological industry, beverages, charcuterie, delicatessen, handicrafts, cultural and religious traditions, among others (Chomicki et al., 2020). The fruits can be cylindrical, oblong or rounded, depending on the cultivar; provided with a thick wax in the epidermis when they mature and reach a weight of up to 13.67 kg (Pandey et al., 2015). The seeds, located in the center of the fruit, are oval-elliptical, flattened, smooth and colored light yellow, they measure between 1.0 and 1.5 cm long and 0.5 to 0.8 cm wide, however, their dimensions vary with the shape of the fruit (Pradhan et al., 2020). In Colombia, it has been little investigated and therefore different aspects such as morphological and biometric variability of the seeds are unknown. Biometric studies of fruits, seeds and their associated traits have made it possible to understand the genetic variability of a population (Ekeke et al., 2019), to base the knowledge related to the propagation and germination of seeds (Steiner et al., 2019), and serve to understand the yield, quality and postharvest handling of fruits and seeds (Cañadas-López et al., 2018). On the other hand, the analyses of the morphometry, viability and germination of the seed are key in the production and commercialization of seeds with excellent physiological quality and in the knowledge of the exogenous stimuli that can impair the embryo (Hartmann-Filho et al., 2016). The tetrazolium test is important for assessing seed viability and its application depends on the protocol of each species. Therefore, in the standardization of this test, seed preparation, tetrazolium solution concentration and staining time are important. These standardization efforts are significant because they directly influence the intensity and uniformity of the seed staining process and, therefore, the evaluation and interpretation of the results compared to conventional germination tests (Souza et al., 2010). The objective of the study was to evaluate the morphometry, viability and germination of B. hispida RESUMEN El objetivo del estudio fue evaluar la morfometría, viabilidad y germinación de semillas de B. hispida, en la Universidad de Córdoba, Colombia. Se midieron ocho características biométricas en una muestra de semillas tomadas al azar de un compuesto balanceado originado de 50 frutos. La descripción morfológica externa e interna se hizo en una muestra de 10 semillas. La viabilidad de semillas se estimó mediante la prueba de tetrazolio, usando la combinación de dos tiempos de tinción (2 y 3 horas) y tres concentraciones de (0,5; 1,0 y 1,5%), bajo un diseño completamente al azar, con seis tratamientos y cuatro repeticiones de 50 semillas. La prueba de germinación (PRUGER) se realizó en casa malla con cuatro repeticiones de 50 semillas para estimar ocho parámetros fisiológicos de germinación. Las características morfo-métricas grosor, longitud y ancho de semillas mostraron reducida variación fenotípica, en comparación con el peso, densidad y volumen de una semilla, con coeficientes de variación mayores que 11,7%. La semilla, ovoide y aplanada, presenta un embrión con sus cotiledones envueltos en una membrana protectora. La viabilidad, determinada con tetrazolio, fue de 89,5-96,5%, mientras que la PRUGER fue de 100%, sin diferencias estadísticas entre ellas (P≥0,05). La combinación de 0,5% de tetrazolio con 2 horas, son suficientes para determinar la viabilidad de semilla. La germinación transcurrió desde los 6 hasta los 19 días después de la siembra, con índice de velocidad germinativa de 0,22, germinación diaria media de 5,26%, valor pico de 5,33 y valor germinativo de 28. Palabras clave adicionales: calabaza de invierno; características biométricas; prueba de tetrazolio; calidad fisiológica. Received: 10-09-2020 Accepted: 16-11-2020 Published: 10-12-2020 INTRODUCTION 2 ESPITIA-CAMACHO / VILLALBA-SOTO / ARAMENDIZ-TATIS / CARDONA-AYALA Rev. Colomb. Cienc. Hortic. seeds, to generate basic information for the conservation, sustainable use and quality control of the seed. MATERIALS AND METHODS The study was carried out between August/2016 and July/2017 in the laboratory of Genetics and Plant Breeding of the University of Cordoba (Monteria-Colombia). The seeds used in the study consisted of 50 fresh, complete, healthy, mature and free pollination fruits taken randomly at harvest in a batch of 0.5 ha of B. hispida. From each fruit 50 seeds were taken at random, to form a balanced compound, which was stored in a cold room ± 5oC (Espitia et al., 2017; Ekeke et al., 2019). The morphometric characteristics were estimated in a sample of 100 seeds taken randomly from the balanced compound originating from 50 free pollination fruits. Eight biometric characteristics of the seeds were estimated: maximum seed width (AS), maximum length (LS) and maximum thickness (GS), measured in cm using a Spictools® vernier. Likewise, the weight of one seed (P1S) and the weight of one hundred seeds (P100S) in g were estimated, in a precision balance 0.01 g, number of seeds per kilogram (NSK), estimated by counting the number of seeds in five samples of 100 seeds, then the average was taken to kg by the respective expansion factor, the volume of a seed (V1S) was estimated in mL as the average increase in volume that is generated in a test tube with a known distilled water volume when introducing a sample of 100 seeds taken at random, and the density of a seed (D1S) was estimated from the ratio (P1S/V1S). In the external and internal morphological description, the essential anatomical parts of 10 complete and healthy seeds were identified and described, following the methodology proposed by Niembro (1988). The seeds were hydro-pressed in distilled water for 12 h at a constant temperature of 27°C. Subsequently, the seed coat was separated and the internal parts of the seed were fully exposed for description and performance of the tetrazolium test (MAPAB, 2009). The viability of the seeds studied through topological patterns is used to compare and characterize the staining of the seeds through three categories proposed by Rao et al. (2007) and MAPAB (2009): Category 1: Viable seeds that have fully stained embryo and endosperm, sometimes with superficial necrosis in the middle of the endosperm in the regions furthest from the embryo and behind the radicle. Category 2: Non-viable seeds that present the embryo and endosperm unstained, or at least one of the two is stained, the embryo and radicle apex may present acute necrosis or there is serious damage in more than half of the essential parts of the seeds. Category 3: Doubtful partially stained seeds, where more than half are unstained, have healthy essential parts and can produce normal or abnormal seedlings, depending on the intensity and pattern of the staining. For the characterization of topological patterns, preconditioned and cut seeds were immersed in a 1% solution of 2,3,5-triphenyl tetrazolium chloride, with a staining time of 2 h (Pinto et al., 2009; MAPAB, 2009). Subsequently, the seeds were introduced into a DIES® oven at a temperature of 40oC (Espitia et al., 2017), then they were washed three times with distilled water to remove the excess of the dye and the staining of the tissues was observed with the help of a Vista Vision® stereoscope. For the variation in the seed staining patt