Mutations induced in some Egyptian cowpea varieties with yield characteristics and high nutritional value using gamma rays and evaluation by microsatellite markers

Abstract

Purpose In order to achieve mutations with enhanced economic, productive, and nutritional characteristics in the two Egyptian cowpea varieties, Dokki 331 and Kaha 1, the application of gamma irradiation at different doses is employed. Additionally, this method aids in distinguishing between these mutations using simple sequence repeat (SSR) analysis. Materials and methods Two different cowpea cultivars were subjected to varying doses of gamma radiation ranging from 50 to 300 Gy. In order to analyze the effects of radiation, both unirradiated and irradiated seeds from both cultivars were planted using a randomized complete block design. This experiment was conducted over a span of six generations, namely M1, M2, M3, M4, M5, and M6, starting from April 2017 and continuing until 2022. Among the various radiation doses, the cultivar Kaha 1 produced promising traits when exposed to a dose of 150 Gy, while the cultivar Dokki 331 showed favorable traits when exposed to a dose of 300 Gy. These traits were further cultivated and studied until the M6 generation. Results Induced mutations in two Egyptian cowpea varieties, Kaha 1 and Dokki 331, are subjected to varying doses of gamma radiation (0, 50, 100, 150, 200, 250, and 300 Gy). Morphological and genetic variations were observed, with mutations being induced at doses of 150 Gy for Kaha 1 and 300 Gy for Dokki 331. The mutation in Kaha 1 (beam 1) resulted in dwarfism, altered leaf shape, early flowering, increased peduncles, pods, and pod seed numbers, ultimately leading to enhanced seed production and acreage productivity. In Dokki 331, the mutations primarily affected pod color, resulting in greenish-brown pods with mosaic seeds, segregating black and gray seeds from the mosaic ones. These mutations led to an increase in the nutritional value of the seeds, including higher nitrogen content, total free amino acids, crude protein, total carbohydrates, and total sugars. The genetic diversity of the seven cowpea mutations was assessed using 20 microsatellite markers. The analysis revealed a total of 60 alleles, with an average of three alleles per locus. The allele frequency ranged from 0.2857 to 1.0, with an average of 0.6036. Gene diversity varied from 0.0 to 0.8163, while the heterozygosity was mostly zero, except for one primer (VM 37) with an average of 0.0071. The polymorphic information content (PIC) ranged from 0.7913 to 0.0, with an average of 0.4323. The Marker Index value ranged from 0.36 to 0.0, with an average of 0.152. Overall, our findings demonstrate the successful induction of mutations in Egyptian cowpea varieties using gamma rays, resulting in improved yield characteristics and nutritional value. Conclusions Radiation as a physical mutagen is highly regarded for its effectiveness, affordability, speed, and safety in inducing mutations. Utilizing gamma rays, we successfully derived a novel cowpea variety called beam 1 mutation, which has gained approval from the Egyptian Ministry of Agriculture.