Development of Maize Haploid Inducer Lines and Doubled Haploid Lines in Pakistan

The work on maize doubled haploid development has started at the Maize Research Station, Ayub Agricultural Research Institute, Faisalabad, Pakistan during 2010 in collaboration with University of Agriculture Faisalabad, Pakistan. The aim of current study was to develop locally adopted maize haploid inducer lines utilizing cheap and easy source of Stock6 and indeterminate gametophyte mutant ig1 gene lines imported from Maize genetic Coop Stock Centre. The lines were later utilized to produce doubled haploid inbred lines. The environmental conditions of Faisalabad are extreme in nature. In spring crop during pollination period temperature may reach up to 45°C. Therefore, locally adopted haploid inducers are needed. Best performing local inbred lines were screened having branched heavy tassel, bold seed, good pollen shedding ability and vigor. These lines were utilized as female donor parent while imported lines as recurrent pollen parent in back cross breeding program until BC4 generation. These lines were selfed twice until BC4F2 and evaluated for haploid induction rate (HIR). Lines with high HIR were further intercrossed to achieve maximum transgressive segregation. Mass selection for the adaptation traits was exercised for individual F2 plants followed by ear-to-row plantation of selected progeny. Four best haploid inducer lines with HIR up to 5% having very good tassel size, height and heat stress tolerance were selected in 2014. Haploid seeds collected in different induction crosses until 2012, were used for colchicine doubling treatment. The doubling percentage of the haploid plants was very low 0.15% and out of 1000 treated seedling 15 survived and only 5 reached up to maturity, where only one D0 cob was harvested. This was successfully selfed and was grown in three different locations for next two seasons and there was no segregation in the successive generations. Developing countries that cannot afford costly haploid inducer lines can work on Stock6 and other cheap sources available free of cost and can develop their own haploid inducer lines well adapted to their own climatic conditions.