While social interactions play a crucial role on the development of young
individuals, those of highly mobile juvenile birds in inaccessible environments
are difficult to observe. In this study, we deployed miniaturised video
recorders on juvenile brown boobies Sula leucogaster, which had
been hand-fed beginning a few days after hatching, to examine how social
interactions between tagged juveniles and other birds affected their flight and
foraging behaviour. Juveniles flew longer with congeners, especially with adult
birds, than solitarily. In addition, approximately 40% of foraging
occurred close to aggregations of congeners and other species. Young seabirds
voluntarily followed other birds, which may directly enhance their foraging
success and improve foraging and flying skills during their developmental stage,
or both.
Intergeneric hybridization was performed between Moricandia arvensis and four inbred lines of Brassica rapa following embryo rescue. Three F1 hybrid plants were developed from three cross combinations of M. arvensis × B. rapa, and amphidiploids were synthesized by colchicine treatment. Six BC1 plants were generated from a single cross combination of amphidipolid × B. rapa ‘Ko1-303’ through embryo rescue. One BC2 and three BC3 plants were obtained from successive backcrossing with B. rapa ‘Ko1-303’ employing embryo rescue. Alloplasmic and monosomic addition lines of B. rapa (Allo-MALs, 2n = 21) were obtained from backcrossed progeny of three BC3 plants (2n = 21, 22 and 23) without embryo rescue. An alloplasmic line of B. rapa (2n = 20) degenerated before floliation on 1/2 MS medium due to severe chlorosis. Allo-MALs of B. rapa (2n = 21) showed stable male sterility without any abnormal traits in vegetative growth and female fertility. Molecular analyses revealed that the same chromosome and cytoplasm of M. arvensis had been added to each Allo-MAL of B. rapa. This Allo-MAL of B. rapa may be useful material for producing cytoplasmic male sterile lines of B. rapa.
The alloplasmic line of radish carrying Brassica maurorum cytoplasm was obtained from four backcrosses (BC) of the amphidiploid hybrid (B. maurorum · Raphanus sativus) to radish. Eight BC 1 plants (2n = 26) and one BC 2 plant (2n = 22) were generated only by using embryo rescue, and two BC 3 plants (2n = 19, 20) were obtained by repeat pollinations after unbagged bud pollination and without embryo rescue. After successive backcrossings with 10 radish cultivars to BC 6 generation, the resulting alloplasmic line of radish (2n = 18) showed stable expression of male sterility without any recognizable changes in vegetative growth and female fertility. This cytoplasmic male sterility (CMS) line of radish was dissimilar to the other existing CMS lines with respect to cytogenetic and molecular characteristics. The novel CMS line produced in the present investigation may be a versatile germplasm for F 1 hybrid seed production of radish.
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