Plant Breeding Research Research Articles

Announcements

THE Council of the Royal Society of Edinburgh has awarded the Makdougall-Brisbane prize for the period 1944–46 to Dr. William Black, of the Scottish Society for Research in Plant Breeding, for his work dealing with genetical investigations on the potato, with their practical applications.

Scottish Society for Research in Plant Breeding

THE report for 1940 of the director of the Plant Breeding Station at Craig's House, Edinburgh, includes several important practical results of scientific research. It is shown that the renovation of semiderelict pastures is best performed by ploughing up and re-sowing. A nurse crop of Sandy oats to be grazed in July, and a mixture of varieties of one grass species, together with wild white clover, are found to be preferable to sowing a mixture of grass species under rape or a seeding nurse crop of oats.

Research in Plant Breeding

SUPPLEMENT 2 of Plant Breeding Abstracts, which has been issued by the Imperial Bureau of Plant Genetics, Cambridge (price 5s.), gives a concise account of work carried on during 1932-35 on crop plants in the British Empire. It shows the great variety of plants grown and the large amount of work in progress on such crops as wheat, cotton, rice, sorghum, coco-nut, apples, etc., gleaned from more than four hundred reports in various parts of the Empire. It is so arranged that one can see at a glance, for example, the investigations of coffee that are being made in Mysore, Ceylon, Uganda, Kenya and Tanganyika, or of strawberries in England, Scotland, Canada, New Zealand and New South Wales. Work on cytology and on the genetics of plant parasites is included, and the whole serves as a very useful summary for plant breeders and geneticists. This outline picture also shows that a surprising variety of economic plants is undergoing genetic improvement.

STUDIES IN THE PHYSIOLOGY OF THE VIRUS DISEASES OF THE POTATO

SUMMARY.The present investigation is concerned with the differences between the nitrogen metabolism of healthy and leaf‐roll affected potato plants.Diurnal estimations were made of the total nitrogen as well as the following nitrogen fractions, ammonia N, asparagine N, amino‐acid N, nitrate N, residual N and protein N in the leaves and petioles of healthy and leaf‐roll infected Arran Victory and President. Weekly determinations of total nitrogen and the above nitrogen fractions were also made in the laminae of Arran Victory and President throughout the growing season.Evidence is presented to show that there is apparently no fundamental difference in the nitrogen metabolism of healthy and leaf‐roll plants, and that the formation of nitrogenous compounds proceeds along the same lines in the two cases.A theory is put forward to account for protein synthesis direct from nitrate N, and not via amino‐acids. The problem of translocation is also discussed, and it is considered that the residual N fraction plays an important part in nitrogen transport.We wish to express our indebtedness to Mr William Robb. F.E.S.E., for reading the manuscript and making a number of suggestions. We would also like to take this opportunity of thanking Dr W. H. Pearsall, of the Botany Department, The University, Leeds, for his help and assistance in a number of different directions. This work was carried out at the Station of the Scottish Society for Research in Plant Breeding, Corstorphine, Edinburgh, under a scheme supported by a grant from the Empire Marketing Board.

STUDIES IN THE PHYSIOLOGY OF THE VIRUS DISEASES OF THE POTATO

SUMMARY.The present investigation was concerned with the formation of carbohydrates in healthy and crinkle infected potato plants, and the nature of the sugar or sugars of transport. A series of observations were also made to determine whether there were any differences in the carbohydrate metabolism when a latent virus (paracrinkle) was present in a variety.The varieties used were Arran Victory for crinkle and President for paracrinkle.The disease was transmitted by stem‐grafting to our virus‐free units with Irish Chieftain for crinkle and King Edward for paracrinkle. All plants were grown in insect‐proof greenhouses.A series of experimental runs were then carried out at different times in the season. Samples of laminae and petioles were taken at hourly intervals over nineteen hours for crinkle and at two‐hourly intervals over twenty‐four hours for paracrinkle.It was found that in the early stages of the disease there was no statistically significant difference between carbohydrate formation in healthy and crinkle plants. The chief differences that were detected were (1) that the percentages of all three carbohydrates that were estimated (hexose, sucrose and starch) were higher in the diseased material than in the healthy, and (2) thatthere was a time lag of approximately two hours between the maximum and minimum points in the crinkle and healthy laminae; the former preceding the latter.Sucrose was found to be the sugar of transport in both cases.In the later part of the season, significant differences were discovered in the two cases. Sucrose was found to show a marked accumulation in the diseased laminae, and it was ascertained that this sucrose was formed by the hydrolysis of starch, whereas in the healthy laminae the formation of sucrose was brought about by synthesis from hexose, which in turn was formed from hydrolysis of starch. A certain amount of the sucrose was also discovered to be produced directly from starch.It was also ascertained that sucrose was still the sugar of transport, but evidence was obtained to show that its passage down the diseased petioles was not so readily effected as in the healthy.The low yields from crinkle infected potatoes is discussed in the light of these results.The presence of a latent virus in a variety was shown to produce no significant difference in carbohydrate formation, either at the beginning or the close of the growing season.This investigation was carried out at the Station of the Scottish Society for Research in Plant Breeding, Corstorphine, Edinburgh, under a scheme financed by the Empire Marketing Board. We would like to take this opportunity of thanking the Director, Mr William Robb, F.R.S.E., and Dr A. Nelson, F.R.S.E., for their helpful criticism in a number of different directions.