Yogesh, VikalRavneet Kaur2017-06-202017-06-202012http://krishikosh.egranth.ac.in/handle/1/5810022051Maize (Zea mays L.) is deficient in the essential amino acids, lysine and tryptophan. The low nutritive value of maize endosperm protein is genetically corrected in Quality Protein Maize (QPM), which contains the opaque 2 (o2) gene along with numerous modifiers for kernel hardness. Two normal inbred lines viz. LM12 and LM13 were targeted for conversion into high quality protein versions using gene based SSR markers located within o2 using two generation marker-based backcross breeding program. DMR7 and CML165 were used as the QPM donor parents. In BC2F1 foreground selection for o2 gene was done using SSR marker phi057 in cross 1 (LM12/DMR7//2*LM12) and with SSR marker umc1066 in cross 2 (LM13/CML165//2*LM13). Out of the total 188 BC2F1 plants of cross 1, 87 heterozygous plants were obtained and similarly in cross 2, 114 heterozygous individuals were obtained out of 206 plants. The BC2F1 plants having o2 allele in heterozygous form were further screened using o2 gene flanking SSR marker and the plants either single or double recombinants, were identified. Whole genome background selection on the single or double recombinants using 104 SSR markers identified three plants with 83.7 to 91.0% recurrent parent genome content in each cross and were selfed to generate BC2F2 population. The three BC2F2 families were subjected to foreground selection and phenotypic selection for kernel modification. Fifty six plants in cross 1 and thirty nine plants in cross 2 having o2 allele in homozygous condition were selfed to generate BC2F3 progenies. The kernels from BC2F2 ears were segregated for hardness of endosperm and showed different levels of modification. In BC2F2 kernels the tryptophan concentration ranged from 0.56% to 0.97% for cross 1 whereas for cross 2 it ranged from 0.58% to 0.91%. 50% opaque BC2F3 lines were evaluated for agronomic traits for selection of single plant progenies to generate BC2F4 progenies.ennullThesis