ABSTRACT

The present study was carried out to investigate the effect of x-ray doses on the germination, survival, growth, yield, proximate, mineral, vitamin compositions and DNA sequence characterization of the fluted pumpkin (Telfairia occidentalis Hook F.) in M1 and M2 generations. The treatments include 0.00 mGy, 6.75 mGy, 10.08 mGy, 14.08 mGy and 18.75mGy. The experiment was set up in a randomized complete block design (RCBD) with five replications. Treated seeds were planted and data obtained in both generations revealed a reduction in germination and survival percentages with increase in x-ray doses. The result showed that there was no significant difference (P>0.05) in germination percentage during M1 generation whereas in M2 generation, germination percentage was highly different when compared to the control.  Observation on the survival percentages also revealed a highly significant difference between the treated plants when compared to the control in M1 and M2 generations. The result of the analysis of variance showed that the effect of the mutagen doses on the leaf area during M1 and M2 generation was not significantly different (P>0.05) when compared to the control. The effect of the x-ray doses on the number of leaves per plant, number of branches and vine length was highly significant (P<0.05). Data obtained on the yield parameters showed that the mutagen significantly enhanced the yield of fluted pumpkin. The result showed that treatment 14.08 mGy significant enhanced all the yield traits studied. The proximate composition of fluted pumpkin was affected by the mutagen treatments during M1 and M2 generations.  Crude protein, moisture and carbohydrate contents showed a significant decrease effect (P<0.05) in both generations whereas crude fibre, ash and fat contents were not significantly different but showed increase greater than the control at different treatment concentration levels. Data obtained on the mineral composition showed that the effect of the mutagen doses on the calcium, phosphorus, iron and nitrogen compositions showed significant difference when compared to the control plants during M1 and M2 generations. The result obtained on the vitamin content of the plant showed that there was a gradual reduction and increase at varying treatment concentrations in the vitamins studied during M1 and M2 generations. The aligned DNA sequence of the treated and untreated sequences reveals all kinds of SNP mutation in the form of indels and nucleotide substitutions. However; the indels were the most occurred. A total of 17 indels were recorded with 5 of cytidine and 4 thymidine, adenosine and guanosine respectively. Cytidine, which had the highest indel occurrence were seen at positions 385, 460, 506, 545 and 551. Thymidine indel which had a total of 4 occurrences were at positions 46, 393, 417 and 472 while 4 guanosine indel were seen at positions 360, 339, 453 and 522 respectively. Adenosine indel were seen at positions 371, 423, 529, and 540. Both the transversion and transition occurred in this study and all were in the ratio 4:1 except for G: T transversion and A:G transition at positions 495 and 87 respectively which both had a ratio of 1:1. A total of 7 transversion were recorded among which were the A:C at position  411, A:T at positions 88, 124, and 352, G:C at position 349 and G:T at positions 474 and 495. While only 4 transitions were recorded which were T:C at location 402 and A:G in positions 87, 435 and 530. These variations reveal the effectiveness of physical mutagens. The observed field performance and variation in physiological traits, proximate, mineral and vitamin levels designed by the DNA polymorphism as induced by different doses of x-ray irradiation reveals the effectiveness of physical mutagens. The variation at different treatment levels is linked to more of genetic effects to environmental as this can serve as a useful selection tool. It is therefore recommended that treatment 14.08 mGy of x-ray should be employed in mutation breeding of fluted pumpkin for improved agronomic traits.