F. J. Stevenson

Kennebec: A new potato variety resistant to late blight, mild mosaic, and net necrosis

SummaryThe Kennebec is a new variety of potato that combines high yield and good cooking quality with a high degree of resistance to late blight in both vines and tubers. In field-exposure tests it has not yet shown the symptoms of mild mosaic or net necrosis. It is late in maturing as grown in Maine, but has been considered medium-late in tests in other States. It is widely adapted. It produces smooth, well-shaped tubers with shallow eyes. Like all other varieties of potatoes, it varies in quality according to the environment in which it is grown and the cultural practices of the growers. As produced in the test plots on Aroostook Farm, Presque Isle, Maine, it has shown excellent market and cooking quality. The keeping qualities in storage appear to be excellent. Kennebec should replace Katahdin in some sections because of its higher yielding ability, its superior cooking quality, and its high degree of resistance to late blight. It should replace Sebago to a large extent because of a higher degree of resistance to late blight and because the tubers of Kennebec are more easily detached from the vines at harvest time than are those of Sebago.

Breeding a potato resistant to the potato leafhopper

SummaryA number of progenies segregated for various degrees of resistance and of tolerance to the potato leafhopper.Of 14 progenies tested three showed a small but significant positive correlation, and one showed a negative correlation between resistance to late blight and resistance to attack by the potato leaf-hopper.Nymphal populations were significantly larger on some seedlings than on others. Correlations calculated between nymphal populations in 1938 and 1939 on 5 progenies did not reach the 5 per cent level of significance.The correlations between nymphal populations and the degrees of hopperburn, with one exception, were not significant. This fact indicates that the variations between seedlings as to the amount of hopperburn were not because of differences in leafhopper populations.The analysis of the 1940 data shows that there were highly significant differences between the varieties and seedlings in nymphal populations and in the amount of hopperburn. Sebago, Sequoia, Katahdin, Rural New Yorker No. 2, and 61 numbered seedlings were significantly more resistant to the potato leafhopper than Irish Cobbler, Warba, Red Warba, Bliss Triumph, Earlaine, and Pontiac.A number of the seedlings were much more resistant and some were more tolerant to attack by the potato leafhopper than were any of the old commercial varieties.

Potato utilization in relation to variety (Heredity) and environment

Potato utilization is a subject that is freely discussed especially in years of surplus. Utilization in its broadest sense includes the use made of potatoes whether consumed in the fresh state, processed before they reach the ultimate consumer, fed to live stock, used for seed, or exported, and regardless of the way in which potatoes are utilized, variety, and the environment in which the potatoes are grown play important parts. In 1952 the total potato production in the United States was 347.5 million bushels. Three and two-tenths million bushels were imported, making a total supply of 350.7 million bushels (1) . Roughly, 74 per cent of the total supply, or 259.1 million bushels, were used fresh: 6 per cent in farm homes, 51 per cent in urban homes, and 17 per cent in restaurants. The total amount processed before reaching the ultimate consumer was approximately 35 miUion bushels, or nearly 10 per cent of the total supply. Feed for livestock and shrinkage amounted to approximately 19 million bushels, or a little over 5 per cent. About 34 million bushels or 10 per cent were used for seed and 3.5 million bushels, or 1 per cent, was exported. It might be noted that in 1952 the amount imported, 3.2 million bushels, was very close to the amount exported. 3.5 million bushels. The data on potato utilization in the United States in 1952 adapted from a table prepared bv A. g. Mercker. United States Department of Agriculture, published by \~Tilliam M. Case in the ~ralley Potato Grower are given in table l.

Factors influencing the germination of seeds of the potato

Summary1.The percentage and velocity of germination of potato seeds was more satisfactory when planted 1/8-inch deep than when planted at a greater depth.2.No significant differences were obtained between covering the seeds with soil, or with 50 per cent soil and 50 per cent sand, or with sand.3.High temperatures reduced the percentage and velocity of germination.4.Alternating the temperature between 20° and 30° was more satisfactory than a constant temperature of 25°.5.A higher velocity of germination was obtained when the seeds and seed-ball debris were allowed to ferment before washing and drying.6.Soaking the seed in an aqueous solution of potassium nitrate did not affect the percentage or the rate of germination.

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.

The Teton potato: A new variety resistant to ring rot

SummaryTeton has shown a high degree of resistance to ring rot over a period of years in Wyoming and Maine. It is not immune from the disease. It produced satisfactory yields in tests in both Wyoming and Maine. In cooking tests made in cooperation with the Home Economics Department of Wyoming Experiment Station, Laramie, Teton was superior to Triumph and Irish Cobbler when baked. When boiled, Teton was superior to Triumph but slightly inferior to Irish Cobbler. Tests for dry-matter content in Maine showed Teton to be lower in this respect than Green Mountain and Mohawk but high enough to indicate good cooking quality.If ordinary sanitary precautions are adhered to, Teton should be valuable in districts where ring rot is a serious menace to potato production.

Resistance of potato seedling varieties to the natural spread of leaf roll

SummaryPotato seedlings were exposed to field spread of leaf roll from adjacent rows in an area where leaf roll spreads consistently year after year. Parents used at first included commercial American and European varieties reputed to be resistant to leaf roll, and a few of the crosses contained some seedlings resistant to the natural spread of leaf roll. When these resistant seedlings were used as parents, the resulting crosses generally were more resistant to field spread than crosses of other kinds. Greater resistance in one of the parents did not always mean greater resistance in the cross. Greater resistance in a cross (on the basis of percentage of seedlings showing any leaf roll) was not necessarily correlated with the percentage of total plants showing leaf roll in the infected seedlings. Field resistance in given seedlings and varieties varied from one season to another on the same farm. Although green peach or spinach aphids (Myzus persicae) probably are an important factor in the field spread of leaf roll, aphid resistance in seedlings is not necessary for field resistance to leaf roll. It is possible to combine field resistance to leaf roll with many characteristics considered commercially desirable in this country.

Potato chip color reversion

SummaryTests with up to 35 varieties indicate that varieties which will show very little color reversion following a range of storage temperatures can be bred and that others will show a relatively high degree of reversion, if summer-harvested and stored for several days at either 50 or 95 F. Not so much reversion occurred when the potatoes were held at 65 or 80 F.

Merrimack: A new variety of potato resistant to late blight and ring rot and adapted to New Hampshire

SummaryMerrimack is a variety of potato bred by the United States Department of Agriculture and tested in New Hampshire. Maine, and elsewhere as part of the work of the National Potato-Breeding Program. Merrimack competed favorably with standard varieties in New Hampshire. It produced satisfactory yields of potatoes, with a relatively high dry-matter content from which excellent chips and french fries were made.In the Maine tests it did not yield as well as some of the standard varieties but in tests it was found to be highly resistant to, if not immune from, the common race of the late blight fungus in both vines and tubers. It is moderately resistant also to early blight, and was apparently fieldimmune from virus A and highly resistant to net necrosis. Its vines are very susceptible to leaf roll virus. Merrimack is not only highly resistant to ring rot but is the first variety released that is highly resistant to both late blight and ring rot. Its multiple-disease resistance should make it valuable, especially to growers who find it difficult to control late blight and ring rot in standard varieties.

The sequoia potato: A recently-introduced insect-resistant variety

SummaryThe Sequoia potato is a high-yielding, late-maturing variety that has shown marked resistance to damage caused by flea beetles and leaf-hoppers.Vine resistance to late blight has been evident, but the tubers are susceptible to rot initiated by the late blight organism. Plants should be sprayed or dusted but probably will not require as intensive a program of spraying as does Green Mountain or Irish Cobbler.Some stem-end browning has occurred under conditions in North Carolina, but thus far it cannot be attributed directly to net necrosis caused by the leaf roll virus. Greenhouse tests conducted at Raleigh may show that the browning is correlated with soil conditions.Sequoia has responded satisfactorily to a wide range of soil and climatic conditions. In North Carolina best results have been obtained on upland soils.Careful attention should be given to spacing and fertilizing. Because of the vigor of this variety, it produces rough, over-size tubers with a tendency to hollow heart condition, if given too much space in the row or if fertilized too heavily.