2. Sweet Corn in Venezuela. The mutation to sugary corn which occurred in a variety of dent corn adapted to the climatic conditions of Venezuela (Maize Genetics Cooperation News Letter, April 1, 1941) has been the basis of the development of sweet corn in this country. This corn has been named VENEZUELA-2 and is now widely distributed throughout the entire country and in other South American countries that have requested it. Some of the details of its development may be of interest.
Until 1942, the majority of the people in Venezuela had never tasted true sweet corn and most of them had never heard of it. Some who had travelled in the United States, imported seeds of a few varieties and planted them in Venezuela, but the plants were always weak, badly diseased, attacked by insects and consequently unable to produce ears.
Corn known as "jojotos" has always been consumed in Venezuela and is sold in the markets of the cities. This is the native type, a mixture between dent and flint, that is harvested not in the milk stage but in the soft dough stage. It is eaten directly from the cob or cut off and used to make certain Venezuelan dishes such as "cachapas", a pancake-like preparation. The true sweet corn now available in Venezuela has such a contrasting flavor to the dent-flint mixture that it is widely accepted by the people of all classes.
In 1939 when a modern program of corn improvement was initiated in Venezuela, approximately 3,000 self pollinations were made in the best local and imported varieties to develop inbred lines. Some of the first generation ears were planted in progeny rows in 1940 and about 3,000 of the best plants were selfed. None of these second generation ears segregated for sweet corn. But one of the second generation plants gave, on selfing, an ear with 216 starchy kernels and 73 sugary kernels. Five plants in the same progeny gave ears with only starchy kernels. Since there had been no sweet corn planted anywhere near these fields and no sugary kernels had appeared in the first two generations of inbreeding, it is extremely likely that this was a mutation to sweet corn.
Fortunately, it occurred in one of the most vigorous lines which had such desirable characters as deep green color, relatively early maturity, two ears per stalk and, most important of all excellent husk covering of the ears.
Some of the sugary seeds and the starchy seeds from this ear were planted and self-pollinated. As was expected the sugary kernels gave ears of 100% sugary type, whereas some of the starchy kernels bred true for starchy and others segregated sugary. Seeds from the sugary ears were planted. When these plants had tassels and pollen, a field of the original variety of starchy corn was nearing the completion of its flowering period. Ten plants in this field were pollinated with pollen from the sweet corn inbred. The seeds from these ten ears were mixed and planted in a small field at the Instituto Experimental de Agricultura y Zootecnia in January, 1942. Vigorous plants were obtained. There was no attempt to control the pollination. All of the ears segregated approximately 25 per cent sugary kernels.
The sugary kernels from these ears were planted in one field and the starchy kernels in another. There was no attempt to control the pollination in either field.
The ears harvested from the first field were of the sugary type, but there was considerable variation in the kernels. Some of them were entirely translucent while others showed various degrees of starchiness.
In the second field where theoretically one-third of the seeds planted were homozygous starchy (Su Su) and two-thirds heterozygous for sugary (Su su), the expected ratio of starchy to segregating ears was 1:2. Actually, there were 9,347 ears with all the kernels starchy and 22,147 ears segregating for sugary.
Theoretically, the segregating ears should have had a ratio of 5 Su to 1 su kernels. One hundred of these ears taken at random gave ratios from 20 Su : 1 su to 3 Su : 1 su, but the total count was 39,742 Su kernels and 9,099 su kernels, or a ratio of 4.36 : 1. This discrepancy from 5 : 1 ratio is probably due to a position effect of the plants in the field.
On October 7, 1942 a demonstration of the history of sweet corn in Venezuela was made to an audience in the auditorium of the Sociedad Venezolana de Ciencias Naturales. At the close of the demonstration, packages of the new sweet corn were distributed to all present. Considerable seed has been distributed since then.
From a scientific point of view this sweet corn will not be of maximum yield because it is the third generation of a cross between an inbred line and a variety. In spite of this, however, it is being distributed because it has yielded sufficiently well to give the public a taste of sweet corn.
Since the first ear of this corn was discovered it has been crossed with a number of selected varieties of ordinary corn which do well under the climatic conditions of Venezuela. The plants from these numerous crosses have been self-pollinated, and inbred lines are being developed in a number of types. When there is an abundance of inbred lines involving the sugary gene, they will be crossed to give hybrid sweet corn for Venezuela. In the meantime the other topcross type will be propagated.
D. G. Langham