INT. J. BIOL. BIOTECH., 16 (1): 129-135, 2019. IMPACT OF GAMMA RAYS ON PHENOLOGICAL, GROWTH AND YIELD ASSOCIATED CHARACTERS IN BREAD WHEAT GENOTYPES Tanweer Fatah Abro 1 , Abdul Wahid Baloch 1 , Zahoor Ahmed Soomro 1 , Mehboob Ali Sial 2 , Wahid Dino Sipio 1 , Muhammad Naveed Tareen 4 , Ayaz Ahmed Lashari 3 , Muhammad Sharif Kakar 4 ,Gul Muhammad Panezai 4 and Ghulam Asghar Baloch 4 1 Department of Plant Breeding & Genetics, Sindh Agriculture University, Tandojam, 2 Nuclear Institute of Agriculture, Tandojam, Pakistan, 3 Agriculture Extension, Dera Murad Jamali, Balochistan, 4 Agriculture Research Institute Quetta ABSTRACT The effect of gamma rays on morphological and yield associated traits of bread wheat irradiated with 150, 200, 250 and 300Gy was observed on newly developed mutant population (M1). The population was developed from four commercial wheat varieties viz., Khirman, TD-1, NIA-Sarang and ESW-9525. The mutation populations originating from four different doses of gamma rays were evaluated along with their mother varieties (non-irradiated) under the field conditions for growth, phenological and yield associated traits in a split plot design with three replications. The present research revealed that means were significantly different (P<0.05) among the genotypes for most of the traits, whereas treatments also created significant variations for some of the traits. Thus, these genotypes and treatments (Gamma rays) can be utilized for further breeding programs to improve bread wheat for various traits. Among the doses, the lowest dose (150 Gy) exhibited desirable results for most of the traits, referring that low dose of radiation may be useful in order to achieve better results for various quantitative traits. Considering the mean performance among the mutants, the TD-1-mutant showed outstanding performance for majority of the traits, followed by NIA- Sarang-mutant. Of special note, the mutants of TD-1and NIA-Sarang were found to be promising for variety of traits, suggesting that TD-1 and NIA-Sarang mutant can extensively be used in breeding programs, so that bread wheat can be improved with respect to growth, phenological and yield associated traits. Keywords: Mutation, gamma irradiations, wheat varieties, yield associated traits INTRODUCTION Wheat, Triticum aestivum L., belongs to the family Poaceae is considered as staple cereal crop in the World. Due to main consumption of wheat in human diet and wide adaption makes it one of the most important crops in the world (Farzi and Bigloo, 2010). There is limited genetic variability among the existing wheat genotypes; however, to enhance the genetic variability Muller (1927) and Stadler (1928) initiated the mechanism of induced mutation which became an important tool in plant breeding. Mutation breeding has very significant contributions in various crops for improving agronomical traits (Maluszynski et al., 1995). Induced mutation can improve the existing genotypes for certain specific traits. Induced mutations have been successfully used in major crops such as wheat, rice, cotton and barley (Ahloowalia and Maluszynski, 2001). Different kinds of radiation such as alpha, beta and gamma rays are being used for inducing mutation among the existing wheat genotypes. The utilization of radiation enables the plant breeder for selecting the highly diverse mutant genotype. Gamma rays are highly penetrating radiation with high level of energy in comparison to alpha and beta (Kovacs and Keresztes, 2002). Agronomical, physiological and other yield contributing characters of wheat can be improved by treating the wheat genotypes with gamma rays (Kiong et al., 2006). Although advance molecular techniques such as embryo culture, tissue culture and pollen culture have also been developed for improvement of crops, but still induced mutation remained of prime importance due to existence of rare type of beneficial mutants. Till to date, more than 3088 varieties of different crop species have been produced through mutagens (FAO, 2014). Different researchers have studied the effect of gamma rays. Rao (1975) reported that there will be drastic effect on quality of wheat if dose is above 5 kGy. Similarly, Ghafoor and Siddiqui (1976) found significant difference for number of tillers and plant height in wheat varieties after exposing to gamma irradiation. Choudhry (1983) applied 10-14 kr gamma rays to dry grain of wheat varieties for evaluating germination percentage, and found that germination increase, on applying lower dose in lines having poor germination. Thus, mutation plays an important role to produce highly diverse and promising genotypes. Keeping in view the above facts, the current study was carried out with the aim to determine the effect of gamma irradiations on growth, phenological and yield associated characters in bread wheat genotypes.