Influence of genetic contamination on seed yield and quality of IR50
1988
Selvaraj, J.A. | Subramanian, P. (Tamil Nadu Agricultural Univ., Coimbatore (India). Seed Technology Dept.)
The effect of cultivar TKM 9 as a contaminant on seed yield and quality was studied in a pure seed crop of IR50 over successive generations of seed multiplication. Field experiments were conducted under irrigated conditions during the dry-wet-dry seasons 1986-87. IR50 was contaminated by transplanting TKM 9 at 2, 4, 6, 8, 10, and 12% in a randomized block design. Pure seed crops of IR50 (T0) and TKM 9 (T7) were included for comparison. Levels of contamination and seed yield and quality attributes - germination and vigor - were correlated negatively. Yield potential and seed quality declined with generation advance. Yield reduction was due not only to varietal contamination, but also to loss in vigor across generations. A slow inbreeding depression in seed vigor caused a subsequent reduction in yield. The pure seed crop IR50 gave the highest yield, germination, and vigor in generation 1; seed yield was reduced 4.6% by generation 3. A contamination of 2% reduced yield 42.5%. Germination and vigor declined by 7 and 20% and 24.5 and 45.4%, respectively. Under the present system of seed production, seed is multiplied across four generations - breeder, foundation, and certified 1 and 2. The observed reduction in seed yield and vigor by the third generation highlights the need for renewal of seed stock after 3 years of multiplication
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