STUDIES ON THE EXTENT OF GENETIC CONTAMINATION IN SEED PRODUCTION OF EXERTED STIGMA TOMATO (Solanum lycopersicum L)

Studies were conducted at the experimental farm of Punjab Agricultural University, Ludhiana, during Rabi season for three years, 2006 to 2010 to standardize the minimum isolation distance required for maintaining genetic purity in hybrid seed production of exerted stigma (recessive) tomato under open field conditions. The exerted stigma seed parent with recessive potato leaved seedling marker was sown at 25 m, 50 m, 75 m, 100 m, 150 m, 200 m and 250 m distance away from normal stigma (inserted) contaminator parent cv. Castle Rock having dominant cut leaf seedling marker. The pooled data of three years indicated that the highest percentage of genetic contamination of 9.26% was recorded at a distance of 25 m from the contaminator (Castle Rock). It was also observed that there was a gradual reduction in contamination level with increasing distance at 100 m isolation distance of 2.56% although it was not within the prescribed maximum permissible limit of genetic contamination (1 and 2% for foundation and certified seed, respectively). There was zero genetic contamination at the highest isolation distance of 150 m. In the present study, in the isolation distances studied until 100 m, the level of contamination was well above the permissible minimum seed certification standards (98% genetic purity for certified seed). However, based on the present study, the isolation distance required for maintenance of genetic purity of tomato using exerted stigma seed parent for hybrid seed production under open field conditions of Punjab is 150 m as against the recommended isolation of 25 m and 100 m for production of certified seeds of open pollinated seeds and hybrid seeds, respectively.