Initiation of early breeding in a population of Microtus townsendii (Rodentia) with the secondary plant compound 6-MBOA

Summary Feeding the secondary plant compound 6-Methoxybenzoxazolinone (6-MBOA) during winter to a free living population of Microtus townsendii accelerated breeding in females. Both the recruitment of young and sexual maturation of these young were advanced by four weeks in comparison with a control population. Overwintered females supplied with 6-MBOA matured at a lower body weight than control females. But there was no such weightat-maturity difference between the grids for males. During April and May 72% of all juveniles captured came from the experimental population. Winter reproduction and early recruitment of young stimulated by 6-MBOA could have important population consequences for these voles.     

Advances in salt tolerance

Summary Advances in and prospects for the development of salt tolerant crops are discussed. The genetic approach to the salinity problem is fairly new, but research has become quite active in a short span of time. Difficulties and opportunities are outlined. Salinity varies spatially, temporally, qualitatively, and quantitatively. In addition, the responses of plants to salt stress vary during their life cycle. Selection and breeding, including the use of wide crosses, are considered the best short-term approaches to the development of salt tolerant crops, but the new biotechnological and molecular biological techniques will make increasingly important contributions. Cooperation is called for among soil and water scientists, agronomists, plant physiologists and biochemists, cytologists, and plant geneticists, breeders, and biotechnologists. Given such cooperation and adequate support for these endeavors, the potential for increasing productivity in salt-affected areas can be realized.     

Optimum prediction of three-way crosses from single crosses in forage maize (Zea mays L.)

Summary Three-way cross means were predicted with formulae involving linear functions of general (GCA) and specific combining ability (SCA) effects estimated from single-cross factorials between genetically divergent populations. Data from an experiment with 66 single-cross and 66 three-way cross forage maize (Zea mays L.) hybrids was used for comparing the prediction formulae. The genotypic correlation (r) between observed and predicted three-way crosses increased with increasing , the weighting factor of SCA effects, for plant height and ear dry matter (DM) content. It displayed slightly convex curves for total and stover DM yield, ear percentage, and metabolizable energy content of stover. For Jenkins' method B, r was considerably less than 1.0 for all traits, indicating the presence of epistasis. The square root of heritability (h) of the predicted means decreased with increasing , the reduction being small with a greater number of test environments. Using the product r·h as a criterion of efficiency, none of the prediction methods was consistently superior and the differences among them were rather small (< 7.5%) for all traits, irrespective of the number of test environments. We recommend evaluating the GCA of a greater number of lines from each parent population in testcrosses with a small number of elite lines from the opposite population. All possible three-way or double crosses between both sets of lines should be predicted by Jenkins's method C. This procedure allows one to select with a higher intensity among the predicted hybrids and thus should increase the genetic gain.Extended version of a paper (Geiger et al. 1986) read at the sixth meeting of the EUCARPIA Section Biometrics in Plant Breeding held at Birmingham, UK, July 28–August 1, 1986     

Somatic hybridization of sexually incompatible top-fruit tree rootstocks,wild pear (Pyrus communis var. pyraster L.) and Colt cherry (Prunus avium x pseudocerasus)

Summary Mesophyll protoplasts of wild pear (Pyrus communis var. pyraster L., Pomoideae) were chemically fused with cell suspension protoplasts of cherry rootstock Colt (Prunus avium x pseudocerasus, Prunoideae), following an electroporation treatment of the separate parental protoplast systems. Fusion-treated protoplasts were cultured, on modified K8P medium, where it had been previously established that neither parental protoplasts were capable of division. Somatic hybrid calli were recovered and, following caulogenesis on MS medium with zeatin and after rooting of regenerated shoots, complete trees were obtained and grown in vivo. Hybridity of these trees was confirmed based on morphological characters, chromosome complement and isozyme analysis. Two separate cloned lines of this intersubfamilial rootstock somatic hybrid (wild pear (+) Colt cherry) were produced. This is the first report of the production of somatic hybrid plants of two woody species, of agronomic value, within the order Rosales.     

朱鹮(Nipponia nippon)的繁殖习性

文章概述了朱鹮的濒危状况及陕西省洋县1981—1986年的繁殖数量,计6年9窝27幼,已知死亡4只,人工喂养3只。 朱鹮在洋县为留鸟,越冬期间偶尔返回繁殖地,2月中旬后不再离开。有显著的领域性。3月上旬开始营巢,中旬至4月初产卵,多数3枚(1—4枚)。孵卵期30天左右,育雏期约为40天,均由雌雄亲鸟共同承担。6月中下旬全窝育成后一起飞离巢区。     

Breeding program for the lesser kudu (Tragelaphus imberbis) in North America

The lesser kudu (Tragelaphus imberbis) has been kept in North American zoological parks since 1930 but has never been a common species in collections. In 1987 this population totaled 28 animals: 15 males and 13 females. A pedigree evaluation in 1987 of the existing population indicated that eight effective founders and one potential founder were represented in the North American herd. Three new potential founders from European captive populations were added to the population in 1987 to increase the number of existing founder lines to 12 animals. As this species is not endangered or threatened in its native habitat, it is not a high priority to qualify for designation as an SSP species. Because of this, the institutions holding lesser kudu in North America decided to join informally and draft a breeding program to better manage this small captive population. This program was designed to minimize inbreeding and equalize genetic representation of founder animals to maximize genetic diversity. It requires a shift in management philosophy to establish stable groups of breeding females at participating institutions while rotating appropriate breeder males through these herds in a controlled manner to ensure minimization of inbreeding and maximization of genetic diversity. It is hoped that this program can serve as a model for the management of other small captive populations of non-SSP species.     

Pollination biology of two species ofKielmeyera (Guttiferae) from Brazilian cerrado vegetation

The pollination biology and breeding systems ofKielmeyera coriacea andK. speciosa, two sympatric woody species common in the cerrado vegetation of C. Brazil, were studied. Both species have similar nectarless, polystemonous Papaver-type flowers which are visited by a similar spectrum of insects, though they bloom in different seasons and are thus phenologically isolated. Large carpenter bees seem to be the most important pollinators and these and other bees effect buzz pollen retrieval despite the fact that anthers are not poricidal. Both species ofKielmeyera possess strong xenogamous breeding systems. The presence of staminate flowers and andromonoecy inK. coriacea, as well as the longevity ofK. speciosa flowers are discussed as alternative strategies to improve pollination success and reproductive efficacy.     

Chromosomal distinction between the red-faced and black-faced black spider monkeys (Ateles paniscus paniscus and A. p. chamek)

The two subspecies of the black spider monkey, Ateles paniscus paniscus and A. p. chamek, can be distinguished by their chromosome number, 2n = 32 in the former and 2n = 34 in the latter. This difference most probably is the result of a tandem fusion between chromosomes 4 and 13 of the original Ateles karyotype (2n = 34) to form a unique metacentric chromosome in A. p. paniscus. Further differences between the subspecies concern the presence of additional interstial or terminal C-bands in chromosomes 3, 5, and 12 of A. p. paniscus. A third difference is that chromosome 12 is metacentric in A. p. paniscus but is submetacentric in A. p. chamek. A. p. chamek shows dimorphisms caused by pericentric inversions in pairs 1, 5, 6, and 7 as well as in the Y chromosome. Since the dimorphisms in pairs 5 and 7 are only found in homozygous condition, they may indicate the existence of geographic variation within this subspecies. Differences in external characteristics possibly reflect these chromosomal difference. The necessity to lend A. p. paniscus full specific status should be considered, since karyologically this is the most distinct one of all forms of Ateles. In captive breeding A. p. paniscus should evidently be treated as a separate population, as hybridization with A. p. chamek may result in offspring with reduced fertility. The intra-subspecific karyological variation in A. p. chamek and its possible consequences for taxonomy and captive breeding require further investigation.     

Measurements of genetic variability for symbiotic dinitrogen fixation in fieldgrwon fababean (Vicia faba L.) using a low level15N-tracer technique

Before starting a breeding program aimed at improving the nitrogen nutrition ofVicia faba, the authors tried an alternative technique to the acetylene reduction assay, to measure some genetic variability in the plant material. The quantity of dinitrogen fixed by several cultivars ofVicia faba was estimated using a low enrichment¹⁵N tracer method and high precision¹⁵N mass spectrometry. The fababeans were cultivated for two years in two different soils. The percentage of fixed dinitrogen in the seed varied between genotypes from 40 to 83% of the total nitrogen and was positively correlated with the total seed nitrogen (r=0.64 to 0.86). A highly significant positive correlation was also found between the total seed nitrogen and the quantity of fixed dinitrogen in the seed (r=0.95 to 0.99). The technique used to measure dinitrogen fixation proved to be useful and reliable enough to discriminate between various genotypes, grown over a period of two years in two different soils. However, several non-fixing control plants showed significant differences in their¹⁵N enrichment and the problem of choosing a good reference plant was raised and discussed.