Establishment of three line system for hybrid cotton seed production

Hybrid yield 20% higher than a conventional pure variety. Utilization of three line system (ABR) in hybrid seed production may reduce production cost up to 60%. Present study is related with establishment of A & B line for hybrid cotton seed production with efficient fertility restoring (R line) system. It comprises three experiments; First experiment was conducted to select high yielding crosses which were used as parent for hybrid seed production. Thirty F1 crosses were grown and standard heterosis were calculated against two standard checks FH-114 and Tarazan-1. Five crosses expressed best performance on basis of high performance in No. of bolls, boll weight and yield. Their female parents (FH-113, Bt 131, Bt 121 and IR-3701 were selected for their conversion into B line. Second experiment was conducted to select CMS plants from FZ generation of exotic hybrids G-72, G-97, RL-2, RL-6, GL-2 and GL-6. Their sterility was confirmed by potassium iodide staining and 29 out of 200 plants showed no staining under microscope and tagged as CMS plants (A line). These plants were manually crossed with selected plants from first experiment for maintaining of CMS plants and establishment of B line. First backcross was successively completed and further backcrosses will be conducted in future. The third major experiment deals with identification of fertility restoration source (R Line) in F1 generation of hybrid seed production. Thirty two fertile plants from exotic hybrids (G-72, G-97, RL-2, RL-6, GL-2 and GL-6) and local varieties (MNH-886, Bt-131, FH-113) were identified, selfed and crossed with identified CMS plants. F1 progeny were evaluated at glass house of NIGAB, NARC Islamabad where segregation analysis were studied. Five plant's progeny (R-1, R-15, R-16, R-17, and R-18) showed fertility up to 99%. Again fertility was confirmed by potassium iodide staining. F1 progeny were subjected to molecular analysis for tagging of fertility restorer gene Rfl. Primer AF-058430 successively tagged Rfl gene with amplification fragment of 360 base pair in R-1, R-15, R-16, R17 and R-18 plants.