Part 6

III

THE BEST IN SEED IS NONE TOO GOOD

A tomato crop may be much poorer than the seed from which it grows but it can be no better.

The tomato seed is short-oval and flattened in shape, covered thickly with short silky hairs. The embryo or baby plant is coiled in a spiral and imbedded in the endosperm (reserve food supply). Three or four years is generally given as the life of the seed but it often remains viable much longer--up to 10 or 12 years in extreme cases. Good seed should germinate 85% to 90%.

Tomato seed sprouts readily, requiring fairly warm temperature, say, 70 deg. to 75 deg. F. for best results. It germinates very slowly at 40 deg. to 50 deg. F.

Breeding

Being a major vegetable crop, the tomato has received much attention from plant breeders. Objectives sought include good cannery type, resistance to the fusarium wilt and other diseases, better greenhouse forms, improved general market and home garden sorts, and varieties adapted for arduous conditions such as hot and dry summers or very short growing seasons.

The tomato is largely but not wholly self pollinated and pollen is not carried far. Thus, it is not difficult to breed to practically a pure-line condition.

Tomatoes for seed are usually ground up and the seed and fine pulp are separated from the skins and coarse material by screening. The juice, fine pulp and seeds are allowed to ferment from 24 to 48 hours, or until the jelly-like pulp is readily washed away. After washing, the seed is dried in thin layers and stored. A bushel of tomatoes may be expected to yield 2-1/2 to 4 ounces of seed and an acre of tomatoes, from 100 to 225 pounds. These vary greatly according to varieties and conditions.

Wellington and others have shown that first generation seed from crosses of suitable varieties show a marked increase of vigor (heterosis or hybrid vigor) over either parent or over the later generations. This fact would seem to offer possibilities in practical use, but it has not thus far proved of value.

Selection Methods

Many growers find it profitable to save their own tomato seed. The plant is an annual, the important characters are quite readily observed and natural crossing is not serious. For these reasons, the enterprise is not as difficult as with most vegetables, although, if done well, it makes heavy demands in labor and care at a time when the grower has much else to do.

The first step in selection is to establish clearly the ideal to be sought, recording it in detail on paper for future reference. Selections should be made on the basis of the plant, not of the individual fruit. It is the plant that is reproduced and the seed from "crown clusters" is no earlier than seed from later settings. The field should be searched soon after blooming time and plants that appear promising should be marked. These plants should be examined three or four times as the season advances, and markers pulled from plants that do not measure up to the desired standard. Suppose ten plants remain; all fruits from each of these may be saved, keeping the seed of each plant separate. All or part of the seed may be planted in separate rows the next year for further selection and to note which parents best transmit their excellent points. If only a small amount of seed is required, direct selections may be made for use in planting for the general crop. If a larger amount of seed is required, seed from one or two of the best plants should be planted in multiplication plats. Off-type plants should be removed from such plantings, but otherwise all the seed may be saved for use. Repeated selection results in constant improvement until the stock becomes a "pure line" or practically so.

Lindstrom of Iowa has led in research on the genetics of tomatoes, chromosome relations and mode of inheritance. Many scientific papers deal with inheritance methods and results. The Yearbook of Agriculture (U.S.D.A.) for 1937 contains a valuable chapter on tomato breeding. It may also be had as Yearbook Separate 1581.

Certification

As with certain other kinds of seeds, certification service for tomatoes has now been set up in several states. Certification is a most useful incentive toward care in breeding and handling and affords valuable assurance to the buyer. It is necessary to know just what is guaranteed by the certificate. It is at the same time wise to be informed as to the inclusiveness and methods of the certification.

The Ideal Variety

In breeding for better varieties of tomatoes, the following are some of the characters to be sought:

(1) A vigorous vine which is necessary to produce abundant fruit and to protect from sunscald.

(2) Resistance to disease especially to fusarium.

(3) High productiveness with moderate number of fruits per cluster--say, 5 to 8.

(4) Evenness of maturity. This is somewhat out of line with the nature of the tomato but much could be accomplished toward the goal of varieties that make their crop and are gone, eliminating long picking periods and the drag of inferior fruit toward the end of the season. The so-called determinate habit of some varieties such as Pritchard is a step in this direction.

(5) Size suitable for expected use and for market demand. Greenhouse tomatoes are generally smaller than those for cannery. Uniformity of size is increasingly important with wide-spread use of the lug-box pack and of small consumer cartons.

(6) Globular to oblong shape is desirable for market but is less important for cannery. Form should be symmetrical, even and smooth.

(7) Color should be deep and rich, fully and evenly developed, inside and out. Red is generally preferred to pink. The difference between red and pink tomatoes does not reside in the flesh but in the presence of yellow pigment in the skin of the former while the skin of the latter is without pigment. Yellow tomatoes are also extant.

(8) Skin should be thick and tough. This safeguards against damage on the way to market and favors ease of peeling. Those saladists who serve sliced tomatoes with skins unremoved, may call for a thin, tender skin but this practice finds no encouragement from discriminating partakers.

(9) Flesh should be abundant in thick walls with a minimum of watery pulp surrounding seeds. In general, a structure of many small cells is desirable.

Varieties