Mutagenic Effects of Gamma Radiation on Eight Accessions of Cowpea (<i>Vigna unguiculata</i> [L.] Walp.)

Abstract

Mutagenesis is used for creating new genetic variability in cultivar improvement. Optimal mutagenic treatment is required for effective mutation induction in crop species. Therefore, radiosensitivity of cowpea accessions to gamma irradiation was investigated. Seeds of eight cowpea accessions were irradiated with 60 Co gamma radiation doses of 100, 200, 300, 400 and 500 Gy. The seeds were sown in pots to evaluate the treatment effects on seed germination (SG), seedling survival (SS) and growth habits of M1 generation. Data were analyzed using descriptive statistics. Low rates of SG (10%-45%) were recorded at higher doses (500-400 Gy) in Ife Brown (IB) and its derivatives, whereas high SG rates (74%-94%) were observed in IT90K-284-2 across all treatments. Percentage SS was inversely related to gamma dosage. A wide range of LD50 for SG (329-1054 Gy) and SS (149-620 Gy) were observed across the cowpea accessions. Low LD50 scores for SG (329-516 Gy) and SS (149-357 Gy) were observed among cowpea with rough seed coat, whereas cowpea with smooth seed coat recorded higher LD50 for SG (521 and 1054 Gy) and SS (449 and 620 Gy). Seed germination LD50 and SS LD50 were highly correlated with mean coat thickness (0.899 and 0.937) than mean seed weight (0.621 and 0.678). Gamma irradiation of cowpea seed at low dosage (100 Gy) increased the vigor of M1 seedlings with respect to primary leaf area, terminal leaflet area, seedling height and plant height at six weeks. Doses of 200 Gy and above resulted in a progressive reduction in vigor of plant and seed setting of cowpea. Radio-sensitivity varied with cowpea genotype and was associated with seed testa texture, thickness and seed weight. Low gamma * Corresponding author. F. O. Olasupo et al. 340 irradiation treatment (100 Gy) may be used to enhance seedling vigor, vegetative growth and yield of cowpea at M1 generation.

Genetic Analysis of Selected Mutants of Cowpea (<i>Vigna unguiculata</i> [L.] Walp) Using Simple Sequence Repeat and <i>rcb</i>L Markers

“…The 32 cowpea genotypes used in this study are listed in Table 1. Twenty three out of the whole 32 plants were selected mutant lines induced by gamma irradiated cowpea seeds [27] [28], while only one line was a mutant induced by UVirradiated pollen of cowpea [29].…”

Dosis óptima de irradiación gamma con Co60 para inducción de mutagénesis en pastos

“…Lo anterior, se debe a que dosis altas de irradiación inhiben las funciones vitales de las células; lo cual puede provocar la muerte del embrión en la semilla. Este fenómeno aumenta conforme se incrementa la dosis de irradiación y es la causa por la que la germinación disminuye (Olasupo et al, 2016). En contraste, el pasto navajita mostró un incremento en germinación de alrededor del 20% con dosis de 100, 200 y 300 Gy.…”

“…Resultados similares fueron encontrados por Aparna et al (2013), quienes encontraron que la velocidad de germinación en cacahuate (Arachis hypogaea) disminuyó al incrementar la dosis de irradiación de 58.4 a 6.8 con dosis de 2300 Gy. Es probable que el retraso en la germinación de semillas irradiadas probablemente se deba a que dosis altas de irradiación, inhiben funciones vitales para la célula como la síntesis de proteínas y la actividad enzimática; esto a su vez retrasa la división celular y por ende la germinación (Chandrashekar, 2014;Olasupo et al, 2016). Por otro lado, en pasto navajita la velocidad de germinación aumentó con las dosis de 100, 200 y 300 Gy.…”

“…Por otro lado, Talebi y Talebi (2012) encontraron este mismo efecto en arroz. Respecto a esto, la disminución en longitud de plúmula y radícula al igual que el retraso en la velocidad de germinación, puede deberse a un retraso en la actividad metabólica y la división celular por causa de la irradiación (Chandrashekar, 2014;Olasupo et al, 2016). No obstante, la LP del pasto navajita mostró incremento en la dosis de 200 Gy, lo cual podría indicar que esta dosis de irradiación estimula los procesos metabólicos y la actividad proteica en esta especie (Chandrashekar, 2014).…”

Radio-sensitivity of cowpea to ultra-violet radiation by pollen treatment

“…The LD50 was determined by adopting the method described in Olasupo et al (2016). Percentage seed setting at M1 generation following hand pollination with UV irradiated pollen were calculated for each treatment.…”