Genetic stability of a synthetic variety

Juan Enrique Rodríguez-Pérez, Jaime Sahagún-Castellanos, José Luis Escalante-González, José de Jesús López-Reynoso, Clemente Villanueva-Verduzco


Synthetic varieties (SVs) have been assumed to be geneticallystable populations through generations. However, it hasbeen recognized that the randomness of the genetic mechanism,the presence of parents with heterozygous genotypes, and the finitesample sizes of the individuals that represent each parent of a SVmay cause gene loss, which may make it difficult to obtain the expectedgenotypic array of a given SV. To study this issue, the numberof non-identical by descent (NIBD) genes in the sample of m plantsof each parental line was considered as a random variable (Ym). Theobjectives were: (1) to determine the mean [E(Ym)] and variance[Var(Ym)] of Ym, and (2) to calculate the average loss of NIBDgenes of each parent (∆NIBD). Parents were assumed unrelated andtheir assumed inbreeding coefficient was F. It was found that E(Ym)and Var(Ym) were 2–Fm and Fm(1–Fm), respectively, and that ∆NIBDwas Fm. Evidently this gene loss was larger as m was smaller andF increased when F < 1. Furthermore, if F < 1 the mean tended to2 as m was larger, whereas the variance and gene loss tended to 0.Finally, if parents are pure lines (F=1) or m is large, Var(Ym) and∆NIBD reduce to 0.

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Phyton. International Journal of Experimental Botany. ISSN print 0031-9457 ISSN en line 1851-5657 Fundación Rómulo Raggio Gaspar Campos 861,  Vicente López, Buenos Aires, Argentina (C.P. 1638) Tel 54 11 4791-0868 / 4796-1456