Impact of gamma radiations on wheat (Triticum aestivum L.) varieties (Batoor and Janbaz)

The present investigation was carried out to evaluate the effect of different doses of gamma rays (15, 25, 35 and 45 Krad) on various morphological and biochemical parameters of two wheat varieties (Batoor and Janbaz). A comparison of the results of different doses with control showed that gamma irradiations significantly affected various parameters. Days to germination were non-significantly delayed in Batoor while significantly decreased at 45 Krad in Janbaz. Germination percentage decreased significantly at 15 Krad in both varieties. Days to spike initiation significantly decreased at 45 Krad in Batoor but increased significantly at 45 Krad in Janbaz variety. Days to spike maturation were increased significantly at 45 Krad in both varieties. Plant height increased significantly at 15 Krad but decreased expressively at 25 Krad and 35 Krad in Batoor. In Janbaz plant height increased significantly at 45 Krad but decreased at 35 Krad. Number of nodes/plant decreased significantly at various doses in Batoor. While in Janbaz number of nodes/plant increased significantly at 15 Krad. Gamma radiation significantly increased number of fertile tillers/plant at 15 Krad in Batoor and at 45 Krad in Janbaz. Number of spikes/plant increased significantly at 15 Krad in Batoor and at 45 Krad in Janbaz. Number of spikelets/spike increased at 15 Krad in Batoor while a decreasing trend was seen in Janbaz with increasing doses. Spike length was nonsignificantly affected by gamma radiation in Batoor variety. However spike length was significantly increased at 45 Krad in Janbaz. Number of grains/spike increased significantly at 15 Krad in Batoor but decreased significantly at higher doses in both varieties. 1000 grain weight significantly increased at 45 Krad in Batoor and at 15 Krad and 25 Krad in Janbaz. Biochemical analysis revealed that gamma irradiation decreased the ash contents significantly at all the doses in both varieties. Moisture contents decreased significantly in Batoor through gamma irradiation except at 45 Krad which showed nonsignificant effect. However, in Janbaz moisture contents increased significantly at 25 Krad. Proteins contents were non-significantly decreased in Batoor, while in Janbaz, proteins contents decreased significantly at 35 Krad.


Introduction
Triticum aestivum is a cultivated wheat species, also known as common wheat or bread wheat and is a member of family Poaceae.Wheat is the major source of food in Pakistan.Pakistan ranks 6th in terms of wheat production, 8th in terms of area but 59th in terms of yield.It adds 12.5% to the value added in agriculture and 2.9% to GDP [1].Wheat is nutritious food which provides proteins, minerals, B-group vitamins and dietary fibers more in quantity than other cereal crop and help in preparation of different types of foods.In general, 70% carbohydrates, 12% water, 2% fat, 12% protein, 1.8% minerals and 2.2% crude fiber are found in the wheat grain kernel.The history of wheat (Triticum aestivum L.) improvement by acclimatization, selection and hybridization dates back to the remote past.Nowadays, mutation induction has become an established tool in plant breeding to supplement existing germplasm and to improve cultivars in definite traits [2].Plants created using mutagenesis are known as mutagenic plants or mutagenic seeds.Mutation breeding has made an official release of over 2700 newly developed crop cultivars in about 170 species [3].Most of the mutant varieties (64%) are developed using physical mutagens such as Gamma rays [4].[5] obtained three high grain yielding and early maturing mutants by treating seeds of Brassica juncea L.cv.S-9 with the combine effect of gamma rays and chemical mutagen i.e., Ethyl methane sulphonate (EMS).[6] developed a new oil seed Brassica napus L.cv ABASIN-95 by induced mutation using gamma rays.[7] Studied the effect of higher doses (30 and 35 Krad) of gamma irradiation on different wheat varieties which created some abnormalities in plant for example, a tiller having two ears attached with each and/or prevalence of sterile ears etc.

Materials and methods
The M2 seeds of two wheat varieties i.e.Batoor and Janbaz were selected for the research project.These seeds were obtained from M1 plants in 2013-14.Gamma irradiation used was generated from the Cobalt-60 source, at Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan.Wheat seeds (M0) were irradiated with 15, 25, 35 and 45 Krad while nonirradiated seeds of each variety were kept as control.An experiment was executed in 2013-2014; M0 plants resulted in M1 seeds which were subjected to experiment in the present study.This study aimed to evaluate the effect of gamma rays in M2 generation.

Field experiment
A field experiment was carried out in botanical garden, Department of Botany, Islamia College Peshawar, during 2014-2015.M2 Seeds of each dose were sown on 24 November 2014 in pots; all pots were equally spaced with equal soil contents in each pot.The experimental design was completely random with each dose having 5 replicates.Equal numbers of seeds were sown in all pots.Parameters The parameters i.e., days to germination, germination percentage, days to spike initiation, days to spike maturation, plant height, number of nodes per plant, number of fertile tillers per plant, number of spikes per plant, number of spikelets per spike, spike length, grains per spike, 1000 grain weight, ash percentage, moisture percentage and proteins percentage were studied during this experiment.

Statistical analysis
Experimental data was statistically analyzed for the Analysis of variation (ANOVA) and least significant difference (LSD) at α = 0.05 using Statistics 10.0 software.

Proximate analysis
Proximate analysis of seeds was carried out at Nuclear Institute for Food and Agriculture (NIFA), Peshawar, Pakistan.

Results and discussion
Gamma irradiation, being known for its mutagenic effect also showed pronounced effect on M2 generation of wheat varieties.Both varieties responded to gamma rays in M2 generation.However, the response was non-conventional; following results explore the findings of present investigation.

Germination percentage
Table 1 show that the lowest germination percentage was recorded at 15 Krad in Batoor and Janbaz (84% and 74%) as compared to control (90% in both).Germination percentage was nonsignificantly affected at 45 Krad in both varieties as compared to control [10] as well observed decrease in germination percentage at radiation doses.[11] find that germination percentage decrease at higher irradiation doses.These results also confirm the finding of [12].Similarly, [13, 14] obtained low germination percentage at irradiation doses.

Plant height (cm)
Table 1 show that in M2 generation of Batoor verity, the highest height was obtained at 15 Krad (67.6 cm) followed by 45 Krad (66.2 cm) as compared to control (61.5 cm).[15] observed the same trend.These results are in agreement with the finding of [16].In Janbaz, plant height decreased with higher doses of irradiation i.e., 15 Krad (70.1 cm), 25 Krad (67.5 cm), and 35 Krad (63.4 cm).The highest height was obtained at 45 Krad (72.5 cm) as compared to control (70.6 cm).[14, 17] have already shown that irradiation doses decrease plant height.observed an improvement in the number of spikes/plant at 15 Krad.In Janbaz, the efficient dose was 45 Krad (8 spikes/plant) as compared to control (3.18 spikes/plant).

Days to spike initiation
[13] obtained mutants that produce higher number of spikes/plant through irradiation doses.
[19] already concluded that gamma irradiation up to 30 Krad has little or no Inhibitory effect on number of spikes/plant.
[22] also observed variation in number of spikes/plant at different radiation doses.In Janbaz a significant increase in moisture contents was obtained at 25 Krad (0.68%) as compared to control (0.35%).

Number of spikelets/spike
[24] observed the same trend.

Proteins contents (%)
Data in Table 3 shows that in Batoor, highest mean value for proteins was obtained at 15 Krad (13.16%) followed by control (13.01%).In Janbaz, mean value for proteins contents was maximum in control (13.97%) and decreased at 35 Krad (13.16%).This decrease could be due to partial nitrogen destruction at different doses.
[27] also observed a decrease in proteins content at higher irradiation doses (Table 3).

Table 1 . Effect of gamma irradiation on different parameters of wheat verities (Batoor and Janbaz) Radiation Doses Days to germination Germination % Days to spike initiation Days to spike maturation Plant height in cm Batoor Janbaz Batoor Janbaz Batoor Janbaz Batoor Janbaz Batoor Janbaz
Data are represented as Mean (n = 05).Means followed by different letter within the column are significantly different (P < 0.05).(ANOVA followed by Tukey LSD test)