Ein neuartig balanciertes Letalfaktorensystem beiLycopersicon esculentum Mill

Summary The abnormal genetic behaviour of plants heterozygous for the chlorophyllmutationgilva is described and was found to depend on the presence of a second zygotic lethal factor with the allele series + —let ^x —let ^y, which constitutes, together withgil, a balanced system of lethal factors of hitherto indescribed action. This system is characterized by two abnormal segregation types existing besides the normal Mendelian segregation ratio: one type is called engspaltend with a narrow segregation ratio of 1,6 green: 1 yellow; the other weitspaltend with a wide ratio of 18,0 green: 1 yellow. The latter is due to the viability of the compound i.e. of a genotype heterozygous for two different mutant alleles of the same lethal factor, a fact of interest from a developmental-physiological point of view.

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, gilva ( , ) , ( ), + —let ^x —let ^y. gil , . (3:1), : (1,6 : 1 ) (18,0 : 1 ). , . . , , .

     

Multivalentbildung und „secondary association“ in den Stadien der Meiosis autotetraploider Rassen der GattungLycopersicon Mill

Ohne Zusammenfassung     

Multivalente Assoziationen in diploiden Pollenmutterzellen der Tomate (Lycopersicon esculentum Mill.) und ihre Bedeutung für das Problem der Chromosomengrundzahl

Zusammenfassung 1. Bei der Tomate (Lycopersicon esculentum) zeigen in den frühen meiotischen Stadien die terminalen Makrochromomeren, die sog. Telomeren, besondere Paarungstendenzen, die eine Persistenz terminal gepaarter Gemini bis in die Metaphase I bedingen. Sie sind zusammen mit der höchstwahrscheinlich ähnlichen unspezifischen Anziehung der Kinetochoren der Anlaß zur Entstehung pseudo-multivalenter Assoziationen in der diploiden Tomate.2. Die in den späteren meiotischen Stadien noch nachzuweisenden Zweiergruppen von Chromosomen werden als Folgeerscheinungen der im Pachytän angelegten Verbindungen gedeutet, die als Matrixverklebung oder chromatische Agglutination wirksam sind.3. Die bei der diploiden Tomate in den einzelnen meiotischen Entwicklungsstadien auftretenden multivalenten Assoziationen können deshalb nicht als Hinweis für das Vorliegen homologer Chromosomen und damit einer niedrigeren Chromosomengrundzahl als n=12 dienen.

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Summary 1. Terminal macro-chromomeres of the tomato chromosomes (Lycopersicon esculentum), so-called telomeres, show special pairing tendencies in the early meiotic phases. These pairing affinities are responsible for the persistence of bivalents being in terminal contact up to metaphase I of meiosis. Terminal affinities of telomeres are together with similar unspecific attractions of kinetochores responsible for the origin of pseudo-multivalents in diploid tomatoes.2. Groups of two chromosomes demonstrable in the later meiotic phases are explained as consequences of pachytene-connections being effective in form of matrix-stickiness or chromatic agglutination.3. Multivalents in the various meiotic phases of diploid tomatoes are for these reasons no proof of the existence of homologous chromosomes and it seems impossible to infer a lower chromosome number than n=12 by their existence.

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1. ( ) (Lycopersicon esculentum) , . (, , , ) .2. , , , , ; .3. , , , , , , n=12.

     

Effects of diseases on reproductive performance in Swedish Red and White dairy cattle

The objectives of this study were to evaluate the effect of diseases on days open (DO), days to first breeding (DFB) and days from first breeding to conception (DFBC) using survival analysis models, and to assess the significance of the sire component and its possible confounding effect. The data consisted of a random sample of 20% of all herds enrolled in Swedish recording system and using 100% artificial insemination with at least 15 Swedish Red and White cows calving in 1991. The follow-up period was from 45 to 145 d after calving. After editing, the data sets had 23,927, 28,197, and 22,089 cows for days open, days to first breeding, and days from first breeding to conception, respectively. The Cox models included parity, calving season, cow milk production and age at first calving as fixed effects, and herd and sire as random effects. Ten disease groups were considered as possible risk factors for the reproductive traits. Disease groups were treated differently if they occurred before or after 45 d postpartum. Diseases occurring in the first 45 d after calving were treated as time-independent covariates and diseases occurring after day 45 were treated as time-dependent covariates for days open and days to first breeding. The percentages of censored cows were 35% for days open, 19% for days to first breeding, and 33% for days from first breeding to conception. Days open increased in cows with dystocia, stillbirth, retained placenta, metritis, or other diseases occurring in the first 45 d after calving, and in cows with metritis, mastitis, or other diseases occurring after 45 d. Days to first breeding increased in cows with stillbirth, retained placenta, milk fever, mastitis, foot and leg problems, or other diseases occurring before day 45, and in cows with metritis, mastitis, foot and leg problems, or other diseases occurring after 45 d. Days to first breeding decreased in cows treated for ovulatory dysfunctions either before or after 45 d. Days from first breeding to conception increased in cows with dystocia, stillbirth, retained placenta, metritis, or ovulatory dysfunctions occurring before first breeding, and in cows with mastitis occurring after first breeding. Although the additive genetic components were significant for all traits considered, the sires did not act as confounders because only a small amount of variability for the traits considered in this study was explained by the sires, with estimated heritabilities of 2% on the logarithmic scale and from 3 to 4% on the real scale.