RESUMO
Despite the continuous breeding that has been conducted with asparagus (Asparagus officinalis L.) since the beginning of the last century, there is little information on parameters for predicting direct and indirect selection response. Yield traits for blanched asparagus production were studied along a two-year period in a half-sib family population planted in Zavalla, Argentina. Half-sib family mean heritability values were low for total yield and marketable spear number (0.31 and 0.35), intermediate for marketable yield and total spear number (0.55 and 0.64), and relatively high for spear diameter and spear weight (0.75 and 0.74). An average increase in marketable yield of 15.9% is expected after each cycle of selection of the top 5% of the families. Total yield failed to express significant genetic correlations with any of the yield components; meanwhile marketable yield showed highly significant relations with market spear number (0.96) and spear weight (0.89). Indirect selection response over yield components (CRx) failed to be advantageous over direct selection (Rx), since the ratio CRx/Rx was always equal or below unity.
Assuntos
Asparagus/genética , Cruzamento , Característica Quantitativa Herdável , Seleção Genética , Asparagus/fisiologia , Modelos Genéticos , FenótipoRESUMO
Callus growth and plant regeneration from long-term callus cultures were studied in two elite clones of Asparagus officinalis cv. Argenteuil, to establish a suitable protocol for a prospective in vitro selection program. Callus initiation and growth was evaluated on MS medium with 3% sucrose, 0.9% agar, 1 mg x l(-1) kinetin, and three levels of 2,4-D. The highest callus relative growth was obtained on medium with 1.5 mg x l(-1) 2,4-D and 1 mg x l(-1) kinetin. Shoot primordia (SP) induction from > 18-months-old calluses was evaluated on several media; the highest percentage of SP induction (89%) and average number of SP per callus (8.6) were obtained with clone "265" on MS medium with 5 mg x l(-1) 2iP, 1 mg x l(-1) IAA, 3% sucrose and 0.9% agar. The highest percentage of root induction (100%) was achieved with clone '265' on MS medium with 0.1 mg x l(-1) kinetin, 0.1 mg x l(-1) NAA, 1.32 mg x l(-1) ancymidol, 7% glucose and 0.8% agar. Important medium x genotype interactions were detected, pointing to the need of adjusting this and other in vitro protocols for specific asparagus genotypes.
Assuntos
Asparagus/crescimento & desenvolvimento , Asparagus/fisiologia , Regeneração , Ácido 2,4-Diclorofenoxiacético/farmacologia , Compostos de Benzil , Células Clonais , Meios de Cultura/química , Técnicas de Cultura/métodos , Citocininas/farmacologia , Ácidos Indolacéticos/farmacologia , Cinetina/farmacologia , Reguladores de Crescimento de Plantas/farmacologia , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/fisiologia , Purinas , Fatores de TempoRESUMO
To estimate the heritability values of characters frequently used as selective criteria, 32 half-sib families obtained from selected plants of three populations of the asparagus variety Argenteüil were evaluated in a randomized complete block design. The following characters were measured: days to emergence of the first spear, number and diameter of spears, number of stalks, plant height and average weight. The values of realized heritability were estimated and were compared with those obtained by the parent-offspring regression method. Phenotypic correlation coefficients between the different variables were significant. The values of realized heritability for most of the variables were moderate to high (between 0.18 and 0.68), except for days to emergence; lower values were obtained by the regression method. As there was a high degree of heritability, additive genetic factors contributed significantly to the genetic variance, which would allow the selection of phenotypically superior plants for asparagus improvement projects.