EVALUATION AND IMPROVEMENT OF DEVELOPED INBRED LINES FOR THE PRODUCTION OF HYBRID MAIZE (Zea mays L.)

Abstract

As a part of hybrid maize breeding program under the Department of Genetics and Plant Breeding, ten single cross maize hybrids were collected from different sources to develop source population and accordingly thirty nearly homozygous lines were raised up to F4 selfed generation, from where the inbred lines were received to advance for next two generations. The entire research work was divided into four experiments and accomplished during the period of 2009-2013. All the field trials were conducted in each rabi season of each year. Only three inbred lines were derived from each of the single cross hybrids. The homozygosity in fifth and sixth selfed generations were tested by some biometrical approaches like paired“t” test, pooled analysis, correlated response and genotypic and phenotypic correlation of fifteen quantitative characters. Of the thirty inbred lines, ten lines yet to be heterozygous for 1-2 quantitative characters and cob girth alone showed maximum heterozygosity in most of the inbred lines which was assessed by significant paired“t” values between fifth and sixth selfed generations. Slow correlated response in between two generations was the indicator of homozygosity among the inbred lines for the quantitative characters. Since self breeding depression was the major barrier in inbred lines development, the negative correlated response for days to 50% tasseling and days to 50% silking had further confirmed the attainment of homozygosity among the inbred lines. Finally the non significant mean differences for each of the fifteen pair of characters of fifth and sixth selfed generations revealed fairly homozygosity among the inbred lines. The genetic diversity in the inbred lines was estimated by Mohalanobis’s D” statistics; thereby the thirty inbred lines were grouped into six clusters. The cluster IV was the biggest and comprised with 8 inbred lines and the cluster III was the smallest which comprised with 2 inbred lines. Both cluster distances and rank distributions were considered in selecting the superior inbred lines for combining ability test. In view of that six parental lines viz. ML01, ML02, ML05, ML1S, ML25 and ML29 were integrated in hybridization operated in a half diallel fashion. The inbred lines, ML01, MLO5 and ML29 appeared as the best general combiners with significant GCA, while the crosses like ML01xML02, ML02xML05, ML02xML29 and ML05xML29 exhibited the significant SCA against GY/P. The simultaneous consideration of SCA and standard heterosis suggested that the F; hybrid (ML02xML29) should be promoted instantly for commercial cultivation by the hybrid maize growers of the country. At the end of the study a total of thirty six treatments were employed with MS, N¢ and three concentrations 2,4-D. The six parental lines were differentially responded to the treatments and finally an effective protocol was developed to utilize in genetic transformation.