Heritable necrosis of red storage cabbage

Research was carried out on heritable necrosis of red storage cabbage. Susceptibility to this type of necrosis depends on 1 incompletely recessive factor n. NN-plants always remain healthy, whereas the majority of the nn-plants become necrotic shortly after the harvest. A number of the Nn-plants also show (mostly weak) symptoms in the second half of the storage period. Minor genes may have an effect as well.Selection for resistance to necrosis should be carried out as late as possible, preferably at the end of the storage period.

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Samenvatting Onderzoek vond plaats over erfelijke necrose bij rode bewaarkool. De gevoeligheid voor dit verschijnsel wordt bepaald door 1 onvolledig recessieve factor n. N N-planten blijven steeds gezond, terwijl de meeste nn-planten korte tijd na het oogsten necrotisch worden. Bij een deel van de Nn-planten treden in de tweede helft van de bewaar-periode dat ook andere genen op resistentie tegen necrose nog een geringe invloed hebben.Voor de selectie op resistentie tegen necrose is hetvan belang dat deze zo laat mogelijk uitgevoerd wordt, dus bij voorkeur aan het eind van het bewaarseizoen.

     

Cytology of tetraploid x hexaploid timothy (Phleum pratense L.)

Ten pentaploids were isolated from seedling populations developed from seed of tetraploid plants grown in association with hexaploid timothy. About 80% of the prophase sporocytes exhibited severe or moderate pycnosis. These pycnotic accumulations appear to arrest the meiotic processes and apparently result in sporocyte lethality. Surviving sporocytes at diakinesis possessed nuclei with configurations that varied from 1 VI+14 II+1 I to 9 II+17 I. It is suggested that the conventional sorts of irregularities (univalents, inversions and translocations) cannot account for the low percentages of stainable pollen. Pairing relations indicated that considerable duplication and/or autosyndesis occurred in the genomes combined, and suggest that even though the tetraploid (2n=28) and hexaploid (2n=42) forms of Phleum pratense are closely related they are not identical. A portion of the sterility observed may be due to nuclear-cytoplasmic interaction.Results of co-operative work of the Crops Research Division, A.R.S., U.S. Department of Agriculture, and the Wisconsin Agricultural Experiment Station, Madison, Wis.Geneticist, Crops Research Division, A.R.S., U.S. Department of Agriculture, and Graduate Assistant, Department of Agronomy, Wisconsin Agricultural Experiment Station.     

The History and Future of Forestry in the Middle Tweed

History is outlined briefly and the more recent developmentsin afforestation and the establishment of plantations are described.The effects of the factors of locality on silvicultural practiceand the problems which will subsequently arise in the futuremanagement of the forests are discussed.     

In memoriam Julius Roth

Ohne Zusammenfassung     

Nekrosen an kartoffelkeimen,ein Symptom von Mosaikviren

Zusammenfassung In Erg?nzung der Angaben vonMartin undQuemener übe eine Fleckung belichteter Dunkelkeime infolge Infektion durch Mosaikviren wurde festgestellt, da? auchNekrosen auftreten k?nnen. Diese sind das Anzeichen einer schweren Erkrankung. Bei den untersuchten Sorten waren sie in der überwiegenden Mehrzahl der F?lle durch Mischinfektion mit Y- und X-Virus verursacht, doch werden nicht alle diese Infektionen durch die Entwicklung von Nekrosen kenntlich. Keime mit Nekrosen bleiben meist in der Entwicklung zurück; bei Farbfleckung ist diese Wachstumsdepression im allgemeinen schw?cher ausgepr?gt.

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Summary Martin andQuemener found that tubers infected with mosaic viruses could be recognized by the irregular spotty coloration which, after exposure to light, developed on sprouts grown in the dark. If the symptoms are very marked (heavy crinkle or streak), especially in the case of mixed Y and X virus infections, necroses appear on the sprouts in addition to or instead of the coloured spots, especially at their bases. These necroses are very different from the nonviral “necrobioses” of the sprout apex or cell elongation zone 1–2 mm below the tip. The necrotic virus spots are of a lighter, brownish colour than the blackish-brown necrobioses, which frequently form stripes running from tip to base. Necrotic sprouts usually exhibit a pronounced decline in growth. Development of sprouts showing only irregular spotty coloration is less inhibited. When examining potato tubers for mosaic virus infection necroses can be regarded as a additional symptom to the irregular spotty coloration. Sprouts 3–5 cm in length grown in the dark were exposed to daylight for some days. The testing of sprouts developed after desprouting gives better results than the testing of the original sprouts. Moreover, the number of tubers with necrotic sprouts increases with increasing sprout age.

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Résumé Martin etQuemener signalent que les tubercules infectès par les virus des mosa?ques peuvent étre reconnus à la coloration en taches irrégulière qui apparait sur les germes cultivés dans l'obscurité lorsqu'on les expose à la lumière. Si les sympt?mes sont tres prononcés (forte frisolée ou bigarrure), surtout dans le cas des infections mixtes à virus Y et X, les colorations en taches des germes sont accompagnées ou remplacées par des nécroses, surtout à la base des germes. Ces nécroses sont toutes différentes des “nécrobioses” non provoquées par des virus, que l'on trouve à la pointe des germes ou dans la zone d'allongement cellulaire à 1 ou 2 mm au dessous de la pointe. Les nécroses à virus ont une couleur brune plus claire que les nécrobioses brun-noir, qui forment souvent des lignes allant de la pointe à la base ddu germe. En général, la croissance des germes nécrotiques est nettement réduite. Le développement des germes présentant uniquement une coloration en taches irrégulière est moins fortement retardé. A l'examen des tubercules de pomme de terre relatif aux virus des mosa?ques, les nécroses peuvent être considérées comme un sympt?me supplémentaire à c?té de la coloration en taches irrégulière. Les germes de 3 à 5 cm de longueur poussés dans l'obscurité sont exposés à la lumière du jour pendant quelques jours. L'examen des germes qui ont poussé après l'enlèvement des germes déjà présents fournit de meilleurs résultats que celui des premiers germes apparus. De plus, le nombre de tubercules à germes nécrotiques augmente avec l'age des germes.

     

THE EFFECT OF WHITE CLOVER AND NITROGENOUS FERTILIZER ON THE PRODUCTION OF A SWARD

Three-year leys of cocksfoot/white clover and cocksfoot alone were dressed with 0, 35, 105 and 210 lb N per acre every year to provide information on the effect of clover and N on production.
Data from the grass-alone swards allowed an estimate to be made of the effect of N on production at different cutting dates. This was compared with the effect of clover.
The effect of N was greater than that of clover in the mid- and late-season cuts. Clover made its greatest contribution, both directly and indirectly, at the first cut, taken in May.
Under very dry conditions (1959), N was more effective than clover in maintaining production and the proportional response was large in relation to that produced under moist conditions.
The results are discussed with reference to the present seasonal use of N on grassland and an argument is advanced for increasing its use in mid-season.     

THE YIELD AND UPTAKE OF PHOSPHORUS BY GRASSES AND CLOVERS

When perennial ryegrass and wild white clover are grown in a phosphorus-deficient soil, there is a difference in the extent to which they use the added phosphorus, especially when the phosphorus supply (potential) is small. In these circumstances the clover makes the better use of the phosphorus. The similarity of the Larsen values obtained with these two species, however, indicates that this must be largely due to the species absorbing the phosphorus at different rates, and not to any interspecific difference in ability to utilize the supply. Both perennial ryegrass and cocksfoot gave higher L values for the hay than for the pasture variety, indicating that slowly-exchangeable phosphorus might be more accessible to the former than the latter. Perennial ryegrass, cocksfoot, timothy, wild white clover and red clover showed minimum values for L at varying times after sowing which were characteristic of the species. This is explained in terms of the isotopic exchange reactions taking place.     

THE EFFECT OF METHOD OF SOWING ON THE ESTABLISHMENT OF GRASS SEED CROPS

Methods used by growers to establish seed crops of perennial ryegrass, cocksfoot, timothy and meadow fescue have been examined. While satisfactory establishments were obtained by sowing perennial ryegrass broadcast, cocksfoot, timothy and meadow fescue should be sown in rows, especially if they are to be sown under a cover crop.     

ANTHILLS AND TERMITE MOUNDS IN PASTURES

The distinctive vegetation of some anthills in chalk grasslands is shown diagrammatically, and some differences between the soils of anthills and those of the surrounding grasslands are discussed. The termite mounds of the tropics also have soils differing from those of the grasslands in which they are built; some harvester termites destroy areas of pasture: and the large mounds of fungus-eating termites hinder mechanical cultivation. Temperate and tropical pastures benefit from control of ants and termites.     

THE EFFECT OF STOCKING DENSITY ON THE PRODUCTIVITY OF YEARLING FEMALE SHEEP

The effect of stocking density on the productivity of yearling female sheep was studied over the 1960 grazing season. The cumulative effect on pasture productivity of previous differences in grazing pressure was eliminated by re-randomization of the pasture after each grazing cycle. Stocking densities from 12 to 30 sheep/acre/unit of time were imposed from March to September, followed by 7 months on a common treatment to measure subsequent effects on animal fertility. Correlations were found between stocking density and (a) liveweight gains, (b) loss of weight in fasting, (c) quality and quantity of herbage residues at the end of the last grazing cycle. Subsequent animal fertility was not measurably affected.