Genetic diversity in chestnuts of Kashmir valley To identify the genotypic effects of parents for wheat × maize crossing system, five F 1 wheat genotypes were crossed with five maize cultivars. The data for haploid seed and embryo production in each cross was recorded and analyzed. The data revealed that maize genotypes have significant variable effects on haploid wheat seed and embryo production. The line × tester analysis proved that wheat and maize genotypes along with their interactions, affect haploid seed and embryo production in wheat × maize crossing system. In this experiment a maize variety named Sadaf showed best performance on the basis of high GCA value as compared to others. It was also discovered that high seed production phenomenon could not be associated with high haploid embryo formation in a wheat × maize crossing system. It was concluded that maize genotypes having great potential for wheat haploid production should be identified and utilized in this system to improve its efficiency as in this study Sadaf is recommended for wheat × maize crossing system. Keywords: Haploid wheat, wheat × maize, genotypic effect, gene interaction, homozygosity INTRODUCTION Doubled haploids (DH) are used for genetic studies like gene interaction, QTL mapping and cytogenetics. DH in plant breeding is the fastest method to attain complete homozygosity in a single generation from a heterogenous population (Mujeeb-Kazi, 2006ab; Akhtar et al., 2012). Production of haploid plants is the most important step for the development of DH. In wheat haploid plants can be produced through in vitro anther culture and wide hybridization (Khan et al., 2012). But high genotype specificity, production of albino wheat plants and poor response of anthers to tissue culture media are main constraints in this technique, resulting in adoption of wide hybridization method. Haploids in wheat mediated through crosses between wheat × hordeum bulbosum were reported by Barclay (1975). But the presence of dominant Kr genes in most wheat genotypes causes incompatibility and hence reduces the haploid embryo formation. The wheat × maize crossing system is the most successful method of viable haploid production. The maize pollen hybridizes with wheat egg cell and produces hybrid zygote. The maize chromosomes are preferentially eliminated from hybrid zygote resulting in haploid (1n) wheat embryos after few mitotic divisions. First haploid embryo production in hexaploid wheat via wheat × maize crossing system was reported by Zenkteler and Nitzsche (1984). Their results were further confirmed by Laurie and Bennett (1986), through a systematic study. The parental genotypic effect on haploid embryo production in wheat × maize cross system is still controversial phenomenon in literature. Studies indicate that haploid production is influenced by wheat and maize genotypes (Verma, 1999). Suenaga and Nakajima (1989) reported that maize genotypes influence the success of wheat × maize crossing system. But Suenaga (1994) found that wheat genotypes significantly affect the crossability. Laurie and Reymondie (1991) observed that in crosses of winter and spring wheat with F 1 hybrid of maize, significant differences for haploid embryo production were present between groups but absent within groups. Suenaga and Nakajima (1993) studied the effects of maize pollen on haploid wheat embryo production and observed differences in haploid embryo production by different maize genotypes on single wheat genotype. The genotypic specificity of the wheat × maize- mediated haploid production system is not up to the magnitude, as reported for other haploid production systems including anther culture (Kisana et al., 1993; Bitsch et al., 1998) and wheat × H. bulbosum (Sitch and Snape, 1986). The genotypic specificity may reduce the efficiency of these systems to a level where they are not applicable to a breeding program. Ovary development and plant formation is affected by wheat genotype and embryo production influenced by maize genotypes. It is suggested that more responsive maize genotypes could be identified to ensure maximum production of haploid plants in this system. In the present study influence of both wheat and maize genotypes Pak. J. Agri. Sci., Vol. 51(2), 363-367; 2014 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 http://www.pakjas.com.pk SADAF- A POTENTIAL DONOR FOR ENHANCING FREQUENCY OF DOUBLED HAPLOIDS IN WHEAT × MAIZE CROSSING SYSTEM Muhammad Ahsan Khan 1,* , Muhammad Kashif 1 , Javed Ahmad 3 , Abdus Salam Khan 1 , Ihsan Khaliq 1 , Fatima Bilquees 2 and Shadab Shaukat 1 1 Department of Plant Breeding & Genetics, University of Agriculture, Faisalabad, Pakistan; 2 Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan; 3 Wheat Research Institute, Ayub Agricultural Research Institute, Faisalabad, Pakistan. * Corresponding author's e-mail: ahsankhanpbguaf@gmail.com