The breeding systems and some interspecific relations of a number of African Trifolium spp.

The breeding systems of 12 species and varieties of Trifolium from Africa were investigated. One annual and the three perennial species were allogamous and self-incompatible, the other annuals were autogamous.The effect of temperature on pollen germination and growth was variable. In some species high temperatures (30°C) adversely affected pollen germination and low temperatures (20°C) in others. A high humidity (93–98% R.H.) was essential for good pollen germination and growth.Approach grafts indicated that these species were closely related, however, this method of grafting may not be as reliable as the cleft graft for assessing species relations. From hybridization attempts between seven species, it appears that some interspecific hybrids may be possible within this group.     

THE EFFECT OF THE BIPYRIDYL HERBICIDES ON HILL COMMUNITIES AND THEIR ROLE IN THE IMPROVEMENT OF HILL GRAZING

The improvement of hill land is important to the national economy of the United Kingdom. An increase in the amount of enclosed productive land results in a greater stock-carrying capacity of a hill farm. Improvement is not always possible by conventional implements, and herbicides are being used to kill the old sward. The bipyridyl herbicides offer a means of destroying or modifying the indigenous vegetation. The application of low doses of paraquat or diquat to an association containing Molinia caerulea, Nardus sfricta and Festuca avina resulted in a change in equilibrium in favour of the fescues. The application of 2 lb paraquat per acre practically eliminates all grass species in a sward and it is then possible to establish desirable pasture species after lightly cultivating the dead surface litter.     

A COMPARATIVE STUDY OF PAPER AND OIL AS CARRIERS OF CHROMIUM SESQUIOXIDE ADMINISTERED TO GRAZING STEERS TO DETERMINE THEIR FAECAL OUTPUT

Two steers excreting similar quantities of organic matter daily were grazed at pasture during the summer of 1961. The four experiments each involved a preliminary period of five days dosing with Cr₂O₃ to reach a fairly constant excretion. The steers received a daily dose of Cr₂O₃ either in oil suspension or in shredded paper. The carriers and steers were interchanged for each trial. For two of the trials each steer in turn was harnessed every other day and all its dung collected in a bag. Total faecal excretion of organic matter was measured from the bagged steer and estimated from the Cr₂O₃ concentration in a composite sample made up from all dung pats voided during the ten-day collection period. In the other two trials the steers were not harnessed and each dung pat was separately sampled and analysed for Cr₂O₃ in the organic matter. The average recovery of Cr₂O₃ in the first two trials was 99·1 (oil) or 94·4% (paper). Calculating the faecal organic matter excretion from the concentration of Cr₂O₃ in the faeces and the quantity given daily overestimated it by 3·5 to 8·0%. There was no significant difference between shredded paper and oil as carriers of Cr₂O₃ for estimating the quantity of organic matter excreted. There were 37% and 22% less variation between dung pats in Cr₂O₃ concentration when this was administered in shredded paper than when given in oil suspension.     

THE EFFECT OF HISTAMINE ON SILAGE DRY-MATTER INTAKE

The oral introduction of 0·5 g histamine as the diphosphate into the rumen of sheep produced no effect on the physiological condition of the animals. The feeding of histamine, as the dihydrochloride, in levels up to 1 g/day to sheep on silage diets did not affect the dry-matter intake.     

WILD WHITE CLOVER SEED PRODUCTION

A survey, covering some 140 fields, totalling 1540 acres, in Kent was conducted in 1961 on the effect of different methods of management on yields of perennial ryegrass and white clover seed. The main results were: (a) the majority of seed growers harvested seed from short-term leys and only a limited acreage of permanent pasture was used for producing seed. Yields of both ryegrass and clover seed were considerably higher on the younger leys; (b) the highest seed yields in 1961 were obtained from fields where sheep grazing was stopped on 24 May. However, a large number of growers continued sheep grazing well after this date: (c) mechanical defoliation, especially when used to supplement sheep grazing, proved an effective method for producing high yields of clover seed; (d) honey bees are important in increasing seed yields, particularly on recently sown leys; (e) combine harvesting from the swath was the most common method of harvesting and no instance of the use of tripods was reported. Seed yields from baling methods were generally low, but direct combining produced a high average yield of clover seed. From these results it was concluded that there was much scope for raising the general level of clover seed yields, especially by giving greater attention to details of management.     

Resistance in tomato to tobacco mosaic virus

The literature on resistance in tomato to TMV is reviewed. The chronological sequence of publication and the relationships between the material of different workers is show graphically. The sources of resistance and the genotype/environment interaction is discussed. The author asks for an increased standardisation of techniques, greater attention to tests for allelism and a responsible attitude when resistant varieties are to be released.There are 54 references     

Germinal pore number in pollen grains as a selection basis in the production of tetraploid clover

Experiments with the variety Fahl of Berseem clover and with different material of red clover have shown that the occurrence of tetraploid and diploid tissues can be detected in a rapid and reliable way by determining the number and arrangement of germinal pores of the pollen. The advantages over the conventional methods are mentioned and described.The determination of the germinal pore pattern, which is combined with pair crossing of the tetraploid heads, makes it possible to obtain in an efficient way completely tetraploid material with a great genetic variability.Samenvatting Proeven met het ras Fahl van Alexandrijnse klaver en met verschillend materiaal van rode klaver hebben uitgewezen dat het voorkomen van tetraploide en diploide weefsels op een snelle en betrouwbare wijze aangetoond kan worden door middel van bepaling van het kiemporiënbeeld van het stuifmeel.De bepaling van het kiemporiënbeeld gevolgd door paarsgewijze kruising van de tetraploide hoofdjes maakt het mogelijk op een efficiënte wijze te komen tot zuiver tetraploid materiaal met een grote genetische variabiliteit.     

LOSSES IN THE CONSERVATION OF HEAVILY-WILTED HERBAGE SEALED IN POLYTHENE FILM IN LINED TRENCH SILOS

A conservation experiment is described in which the losses in ensiling heavily-wilted herbage, of approximately 50% dry matter, in lined trench silos, with and without a polyethylene film seal, are compared. The composition and digestibility of the silages produced in the sealed silos were comparable with those of the original herbage. The content of organic acids in the sealed silos was low, suggesting that fermentation was suppressed by the partially gas-tight seal. In the unsealed silos there was considerable spoilage, 70% of the material being inedible. In the 2 sealed silos losses of dry matter were 8·2 and 5·2% and losses of SE 11·5 and 7·8%, respectively. The losses recorded are compared with those usually encountered in lined trench silos.     

Fertility of hybrids fromSolanum phureja and haploidS. Tuberosum matings

Summary A workable level of male and female fertility is present among many haploids (2n–24) obtained from the common potato,S. tuberosum (2n–48). However, the incidence of male fertility and the seed set obtained following numerous interhaploid matings have been consistently low. Hybrids between the cultivated diploid (2n–24) species (S. ajanhuiri, S. goniocalyx, S. phureja, S. stenotomum) and the pollen-fertileS. tuberosum haploids provide one means of overcoming this low fertility. Crosses were made among 60 F₁-hybrids, resulting fromS. phureja (♀) — haploidS. tuberosum (♂) matings, to determine their pollen and ovule fertility. These hybrids, which represent 16 combinations of 15S. phureja selections (from Plant Introductions 195198, 195214, 225678, 225683, 225685, 225701, 225708, 225710, 243461, 243462, 243466) with 2 malefertile haploids (US-W 1 fromKatahdin and US-W 42 from,Chippewa), were selected for desirable tuber characteristics and yield. All 60 hybrid selections were fertile both as males and as females. The seed set obtained was exceptionally high. No self-fertility was found. The high incidence and level of male and female fertility suggests that lack of fertility is not likely to present an obstacle to future study of the potato at the 24-chromosome level.

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Zusammenfassung Ein brauchbarer Grad von m?nnlicher und weiblicher Fertilit?t ist bei vielen, von der gew?hnlichen KartoffelS. tuberosum (2n–48) erhaltenen Haploiden (2n=24) vorhanden. Dennoch sind das Ausmass von m?nnlicher Fertilit?t und der nach zahlreichen interhaploiden Paarungen erhaltene Samenansatz st?ndig schwach gewesen. Bastarde zwischen den kultivierten diploiden (2n–24) Arten (S. ajanhuiri, S. goniocalyx, S. phureja, S. stenotomum) und den pollenfertilenS. tuberosum-Haploiden stellen eine M?glichkeit dar, um diese schwache Fertilit?t zu überwinden. Fertile, kr?ftige Bastarde, einige davon mit überraschend guter Knollengr?sse und gutem Ertrag wurden erzeug', wenn die Haploiden als Pollenspender gebraucht wurden. Die Bastarde, welche von den reziproken Kreuzungen stammten, waren ebenso kl?ftig, aber m?nnlich-steril. Um ihre Pollen- und Eizellen-Fertilit?t zu bestimmen, wurden Kreuzungen zwischen 60 F₁-Bastarden vorgenommen, die aus Paarungen vonS. phureja (♀) mit, haploidenS. tuberosum (♂) hervorgingen. Diese Bastarde, die 16 Kombinationen von 15S. phureja-Auslesen (aus “Plant Introductions” 195198, 195214, 225678, 225683, 225685, 225701, 225708, 225710, 243461, 243462, 243466) mit zwei m?nnlich-fertilen Haploiden (US-W 1 vonKatahdin und US-W 42 vonChippewa) darstellen, wurden auf wünschenswerte Knolleneigenschaften und Ertrag ausgelesen. 99% der m?glichen 1.770 Kombinationen zwischen den 60 Eltern (1.755 Best?ubungen) und 84% der reziproken Kreuzungen (1.483 Best?ubungen) wurden vorgenommen, indem eine Best?ubung in jeder Richtung angewendet wurde. Der Erfolg nach reziproken Paarungen war mit dem aus Kombinationen, die nur in einer Richtung versucht wurden, vergleichbar (68% und 67% Beeren je Best?ubung). Alle Beeren zusammen brachten einen Durchschnittsertrag von 242 Samen je Beere und 92% ergaben mehr als 100 Samen je Beere (Tabelle 1). Alle 60 Eltern erwiesen sich als m?nnlich- und weiblich-fertil. Keine waren selbstfertil, obwohl alle funktionsf?hige Eizellen und Pollen produzierten. Die Leistungen dieser Selektionen als m?nnliche und weibliche Eltern sind nach Familien zusammengestellt (Tabelle 2). Die Mittelwerte für Einzelauslesen innerhalb einer Familie waren, von weinigen Ausnahmen abgesehen, den Familien-Mittelwerten vergleichbar. Die Zahl der erfolgreichen Best?ubungen zwischen enger verwandten F₁-Auslesen war mit jener zwischen “nicht verwandten” Auslesen vergleichbar (Tabelle 3). Der durchschnittliche Samenansatz war hoch, ob die Paarung zwischen Geschwister-, Halbgeschwister- oder “nicht verwandten” Auslesen erfolgte. Ein Vergleich zwischen den rohen (“raw”) Haploiden vonS. tuberosum und den 60 Bastarden ausS. phureja und haploidenS. tuberosum in bezug auf Triebkraft, Abblühen und Fettilit?t ist auffallend. Im Verlauf einer Vegetationsporiode blühten ungef?hr 50% der Haploiden, zirka 30% wurden erfolgreich als weibliche Eltern verwendet, und 3% waren m?nnlich-fertil (Tabelle 4). Demgegenüber blühten alle Bastard-Auslesen reichlich, und alle waren als m?nnliche und weibliche Eltern funktionsf?hig. Das h?ufige Vorkommen und der hohe Grad von m?nnlicher und weiblicher Fertilit?t weist darauf hin, dass der Mangel an Fertilit?t für zukünftige Studien über die Kartoffel mit 24 Chromosomen kaum ein Hindernis bildet.

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Résumé Il existe chez divers haplo?des (2n=24) obtenus de la Pomme de terre commune,S. tuberosum (2n=48), un niveau exploitable de fertilité male et femelle. Cependant les cas de fertilité male et les quantités de semences obtenues à la suite de nombreux croisements inter-haplo?des sont régulièrement bas. L'hybridation entre les espèces diplo?des cultivées (2n=24) (S. ajanhuiri, S. goniocalyx, S. phureja, S. stenotomum) et les haplo?desS. tuberosum à pollen fertile constitue un moyen de surmonter cette basse fertilité. En utilisant les haplo?des comme parents pollinisateurs, on a obtenu des hybrides fertiles, vigoureux, parmi lesquels plusieurs possèdent des qualités surprenantes de grande grosseur de tubercule et de productivité. Les croisements réciproques donnent des hybrides également vigoureux mais affectés de stérilité male. On a effectué des croisements parmi 60 hybrides F₁, provenant deS. phureja (♀) S. tuberosum haplo?des (♂), pour déterminer leur fertilité pollinique et ovulaire. Ces hybrides, représentant 16 combinaisons de 15 sélections deS. phureja (provenant des “Plant Introductions” 195198, 195214, 225678, 225683, 225685, 225701, 225708, 225710, 243461, 243462, 243466) avec deux haplo?des avec fertilité male (US-W 1 dekatahdin et US-W 42 deChippewa), avaient été choisis pour leurs bonnes propriétés de tubercule et de productivité. 99% des 1770 combinaisons possibles parmi les 60 parents (1775 pollinisations) et 84% des combinaisons réciproques (1483 pollinisations) ont été réalisées en pollinisant dans les deux sens. Les réussites des croisements réciproques et des croisements dans un sens seulement sont comparables (68 et 67% de fructification respectivement). Sur l'ensemble des baies, la production moyenne de semences par baie était de 242; 92% des baies donnaient plus de 100 semences par baie (Tableau 1). Tous les 60 parents étaient fertiles à la fois comme male et comme femelle. Aucun n'était autofertile alors que tous produisaient des oeufs et du pollen fonctionnels. Les performances de ces sélections comme parents males et femelles sont résumées par familles dans leTableau 2. Les moyennes des sélections individuelles au sein d'une famille étaient, à part quelques exceptions, comparables aux moyennes de la famille. Les nombres de pollinisations fécondes parmi les sélections F₁ les plus apparentées étaient comparables à ceux de sélections “non apparentées” (Tableau 3). La production moyenne de semences était élevée, que le croisement implique des sélections soeurs, demi-soeurs, ou “non apparentées”. Les comparaisons de vigueur, de floraison et de fertilité entre les hybrides purs (“raw”) deS. tuberosum haplo?de et les 60 hybridesS. phureja S. tuberosum haplo?de sont frappantes. Au cours d'une saison de croissance, 50% approximativement des haplo?des fleurissent, 30% approximativement sont utilisés avec succès comme parents femelles, et 3% ont la fertilité male (Tableau 4). Au contraire, toutes les sélections d'hybrides fleurissent abondamment et toutes sont des parents males et femelles fonctionnels. Le niveau élevé de fertilité male et femelle suggère qu'un manque de fertilité ne présente vraisemblablement pas un obstacle à l'étude ultérieure de la Pomme de terre au niveau de 24 chromosomes.

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Cooperation of the Inter-Regional Potato Introduction Project in providingSolanum materials is hereby acknowledged. This research was supported in part by a grant from the National Science Foundation.