C. F. Clark

Cooking quality of the potato as measured by specific gravity

ConclusionsThe highly significant interaction between seasons and mealiness indicates that a single season/rss test is not a sufficiently adequate basis for rating the mealiness of a variety.The two methods of measuring specific gravity employed in these tests gave approximately the same results. Since the salt solution method is more rapid, it is preferable to the more laborious method of weighing in air and water.The use of salt solutions of known densities was found to be a practical method for making a preliminary selection for mealiness. The study of large populations can be greatly facilitated by employing this method, since much less time is required than by the usual cooking method. Furthermore, the material tested may be used later for planting.

Artificial light as an aid in potato breeding

ConclusionsThe application of artificial lights to potato plants in the greenhouse stimulated vine growth and blossoming to a remarkable degree. There was a high correlation between the naturally fertilized seed-setting record of the seedlings in the field at Presque Isle, and the extent of blossoming in the greenhouse under the lights. There was little difference in the effects of the 1000 watt and 500 watt lights. Smaller lights than these might produce the desired results.The application of artificial lights facilitated the production of good cytological material. No naturally fertilized seed was produced.Inbred seed was readily obtained under the lights by hand pollinating self-fertile plants. Seed balls, but no seed, were produced as the result of an attempted cross between two varieties, one of which had n = 12 chromosomes, the other n = 24.

Further studies of the origin of russeting in the potato

SummaeyThe results obtained from the removal of the eyes of the Russet Burbank showed no indication of the origin of this variety by mutation though the possibility of its origin as a dichlamyde mutant was not entirely eliminated.Breeding tests in which the factors for russet skin were transmitted through the germ cells suggest that this variety may be of seedling origin.The results of crosses indicate that in the material studied the russet skin of the tubers was the result of the action of complementary factors.In the seedling No. 44537 the russet skin character apparently is due to a mutation. Progeny tests show that it is a gene mutation.

Longevity of potato seed

ConclusionsYearly tests were made of potato seed stored for a period of thirteen years under four conditions; viz.,(1)In envelope, at room temperature.(2)In bottle, at room temperature.(3)In bottle, at 40° F.(4)In bottle, at 32° F. Storage at room temperature was decidedly inferior to cold storage in maintaining the viability of the seed. The envelope container was the least efficient of all storages.Seed stored at 40° F. showed no decline in viability until after II years of storage.The 32° F. temperature not only prolonged the life of the seed to the end of the 13-year storage period, but appeared to have a stimulating effect, since the highest percentages of germination in this lot were obtained during the last five years of the test.

The breeding behavior of the katahdin potato

ConclusionsStudies of the progenies of Katahdin inbred, naturally-fertilized, and crossed with other varieties have afforded considerable information regarding the genetic composition of Katahdin with respect to certain characters as well as the breeding behavior which may be expected when this variety is used as a parent.Katahdin carries one of the complementary factors for red skin color of the tubers. This variety also carries a complementary factor for a light type of russeting.The large number of color classes into which the inbred progeny of Katahdin segregated indicates the presence of 3 basic complementary factors for flower color.Katahdin appears to be heterozygous for at least part of the factors for tuber shape; however, a high percentage of short tuber types may be expected to be obtained when Katahdin is crossed with varieties having short tubers.A large percentage of tubers with shallow eyes may be expected in progenies of which Katahdin is a parent.Katahdin apparently carries 2 heterozygous factors for resistance to late blight.Resistance to mild mosaic has been shown to be transmitted by Katahdin.Evidence has been obtained which indicates that Katahdin transmits resistance which prevails under conditions of natural field exposure to a type of latent mosaic expressed in certain varieties as top necrosis.

New potato varieties

SummaryBreeding potatoes for disease resistance is being emphasized in the cooperative potato-breeding program which is carried on between the United States Department of Agriculture and a number of the State Experiment Stations.A large number of varieties have been produced that are resistant to one of the commonest virous diseases known as mild mosaic. Two of these have been named and are being distributed. One seedling at least is resistant to another virus, latent mosaic. An effort is being made to combine the resistance to the mild and to the latent mosaic in a single variety.Tests of a large number of varieties and seedlings are being conducted to find varieties which show resistance to two other virous diseases—leaf-roll and spindle tuber.Several varieties and seedlings are available which showed resistance to late-blight during the blight epidemic year of 1932. Comparatively no blight developed in 1933 and as a result the field test for late blight resistance was a failure. None of the seedlings apparently resistant to late blight are very promising from the commercial standpoint but the best of them are being used as parents in the work of breeding for blight resistance.

Recent developments in potato breeding: review of literature

This paper, a report of the Research Committee ori Potato Breeding, is intended to serve as a survey of the results which have been accomplished in the various phases of potato breeding, both in the United States and in foreign countries, as shown by papers published during the year I937. A few papers, believed to be of special interest, which appeared late in the preceding year after the publication of the last report, are also included. Much of the material from foreign sources has been derived from the abstracts published by the Imperial Bureau of Plant Genetics, Cambridge, England. The general trenr of potato breeding investigations seems to be toward disease resistance, with cytological studies occupying a prominent position, particularly with respect to wild species and species hybrids. Much has been accomplished in the field of the genetics of the potato by the comprehensive studies of a few investigators.

The improvement of the potato

(3) The highest yields were obtained from sprayed and dusted plots receiving two alternate ap.plications of nicotine dust; there were also marked increases m yield where nicotine had been added to the spray mixture. It will be noted that in Experiment 1 the yield of tubers in the check and dusted plots were much higher than their foliage condition and aphid population would have warranted; otherwise the data tended to show a close correlation between the efficiency of spraying and dusting operations and the yield of tubers. (Table III.)