Genetic Variation for Agronomic Characters in a Burley Tobacco Synthetic Following Recurrent Selection for Increased Black Shank Resistance

Abstract

Black shank, a fuagal disease caused by Phytophthora parasitica var. nicotianae, is a major hazard in the production of burley tobacco (Nicotiutta tubacum L.). Moderate levels of resistance have been bred into cultivars, but little success has been achieved in utilizing high levels of resistance found in the cigar line. Beinhart 1000‐1. Beinhirt 1000‐1 and seven burley cultivars were combined into a synthetic population and three cycles of selection for increased black slunk resistance were conducted. The objectives of this study were (i) t0 estimate genetic variability for agronomic traits in the original base population (Co) and die three selection cycles and (ii) to characterize the effects of selection for black shank resistance on the agronomic traits. Fifty selfed lines From the base population and each of three selection cycles were evaluated in replicated field trials at Lexington and Princeton, KY. Differences among cycle means for six agronomic traits were not statistically significant. Genetic variation for the six traits among lines within cycles was highly significant and did not change during selection. The results indicated that previously assumed associations between black shank resistance in Beinhart 1000‐1 and undesirable agronomic traits were due to chromosomal linkages which were apparently broken by intercrossing. The C3 population would be a useful base population for selection to improve agronomic performance in black shank resistant genotypes.

Sélection récurrente chez les autogames pour l'amélioration des variétés lignées pures: une revue bibliographique. II

“…Cependant, aucune nouvelle expérience de sélection récur-rente basée sur l'haplo-diploïdisation n'a été recensée depuis Patel et al (1985). Plusieurs (Hanson, 1992 (Legg et Nielsen, 1992), des caractères physiologiques ou morphologiques (Matzinger et al, 1989 ; Frey, 1989a et b ;May et Van Sanford, 1992 ;Xu et Wilcox, 1992), et même le rendement en grains (Werner et Wilcox, 1990 (Burton et al, 1983) Frey, 1990Rose et al, 1992 Sanford, 1992 ;Carter et al, 1982 ;Guimaraes et Fehr, 1989 ;Hanson, 1992 ; Burton et al, 1983). Certains utilisent des échantillons restant des individus S 0 ou des familles S 1 testés dans le schéma (Thomas et .…”