Rapid Generation Cycling of Chrysanthemum Using Laboratory Seed Development and Embryo Rescue Techniques

Abstract

<jats:p>The generation time (0.75 to 1.5 years) in perennial, hexaploid chrysanthemums <jats:italic>[Dendranthema grandiflora</jats:italic> Tzvelv. <jats:italic>(Chrysanthemum morifolium</jats:italic> Ramat.)] impedes the rate of progress for sexual breeding programs in creating new clonal cultivars, inbred lines for hybrid seed production, and genetic studies. Modifications to the crossing environment and embryo rescue were evaluated to minimize the chrysanthemum generation cycle. One greenhouse chrysanthemum clone was outcross-pollinated using a bulk pollen source. Following emasculation, inflorescences were either left in situ or the peduncle bases were placed in styrofoam boards floating on a solution of 1% sucrose and 200 ppm 8-HQC under laboratory conditions. Embryogenesis occurred at a faster rate under laboratory conditions as tested with histological techniques; the heart stage appeared as early as the second day after pollination, compared with 11 days using in situ methods. Total embryogenic development time ranged from 25 (laboratory seed development) to 52+ days (in situ ripening). In a second test, embryo rescue (ER) significantly improved percent seed set, percent germination, and percent of progeny reaching anthesis relative to normal development. ER progeny from both garden parents were significantly earlier in total generation time than corresponding non-ER siblings. Laboratory seed development and ER were then used sequentially to obtain an average progeny generation time of =100 days, thus allowing for three generations per year. The potential impact of these two techniques on breeding chrysanthemums and other perennial crops with long generation times is discussed.</jats:p>

Inheritance of Seed Set, Germination, and Day Neutrality/Heat Delay Insensitivity of Garden Chrysanthemums (Dendranthema ×grandiflora) under Glasshouse and Field Conditions

“…Mean outcross seed set (32.8%) was lower than previous reports (36% to 71%) in random outcross pollinations (Ronald, 1974). Such low levels of outcross seed set are attributable to matched S alleles between inbreds and/or inbreeding depression, rather than source-sink interactions (Anderson et al, 1990).…”

“…Seed and ovule counts were made for all pollinations and were pooled for the crossing environments. Rapid generation cycling techniques of laboratory seed ripening and embryo rescue were used as crossing procedures to maximize seed set and decrease generation time (Anderson et al 1990). Percent germination [(∑ no.…”

Inheritance of pseudo-self compatibility in self-incompatible garden and greenhouse chrysanthemums, Dendranthema grandiflora Tzvelv

“…Progenies were grown using rapid generation cycling (Anderson et al, 1990). In all, twenty-four inbreds (at various levels of inbreeding), 30 recombinant inbreds (inbreds with a history of inbreeding juxtaposed with outcrossing to facilitate genetic recombination), and four noninbred cultivars were used.…”

Creating novel chrysanthemum germplasm via interspecific hybridization and backcrossing

“…Endosperm failure is thought to be the major factor underlying the phenomenon of early embryo abortion, a common barrier in wide crossing (Buitendijk et al 1995;Lester and Kang 1998;Ssebuliba et al 2006;Deng et al 2009b;Sun et al 2009). The elaboration of in vitro ovary and embryo culture has done much to improve the success rate of hybrid plant recovery (Anderson et al 1990;Watanabe 1977), including in various combinations of Asteraceae sp. (Abd El-Twab and Kondo , 2001Kondo , 2006Cheng et al 2009;Kondo et al 1999;Tang et al 2009), as well as in the present study.…”