Waxy corn
As this plant showed many peculiar traits, the American breeders long used it as a genetic marker to tag the existence of hidden genes in other maize breeding programs.
Until World War II, the main source of starch in the United States was tapioca, but when Japan severed the supply lines of the U.S., they forced processors to turn to waxy maize[citation needed].
Amylopectin or waxy starch is now used mainly in food products, but also in the textile, adhesive, corrugating and paper industry.
The question was considered closed at the end of the 19th century by De Candolle[3] who stated: "Maize is of American origin, and has only been introduced into the old world since the discovery of the new.
[4] For some scholars it was difficult to conceive that from 1516 on the American plant had had time to penetrate into a wild country inaccessible to foreigners, to produce a mutation, and as such a mutant to spread from the Philippines to Northern Manchuria and the Primorsky region within three to four hundred years.
Secondly, the fact that maize, if introduced into Asia in Post-Columbian times, must have been rapidly accepted merely indicates that, like the potato in Ireland, it met an acute and pressing need.
Although the plants produced such small ears that they could find no place in direct competition with the improved varieties, the possession of this adaptation gave the new type an economic interest, particularly in some parts of the semiarid Southwest.
Consequently, the effort has been made to combine by hybridising the desirable characteristics of this small variety with those of larger and more productive types.
[citation needed] In 1922, another researcher, Paul Weatherwax of Indiana University in Bloomington, reported that the starch in waxy maize was entirely of a "rare" form called "erythrodextrin", known today as amylopectin.
[13] In 1937, just before World War II, G.F. Sprague and other plant breeders at what was then called Iowa State College had begun a crossbreeding program to attempt to introduce the waxy trait into a regular high-yielding hybrid maize.
By this time, the waxy plant no longer had the peculiar structural traits noted by Collins, probably due to years of crossing into various genetic stocks.
At this time, waxy maize was not so important because the main source of pure amylopectin still was the cassava plant, a tropical shrub with a large underground tuber.
[14] During World War II, when the Japanese severed the supply lines of the States, processors were forced to turn to waxy maize.
From World War II until 1971, all the waxy maize produced in the U.S. was grown under contract for food or industrial processors.
Feeding trials were set up which suggested that the waxy maize produced more efficient weight gains than normal dent.
[citation needed] Waxy endosperm is inherently a defect in metabolism, and its low frequency in most maize populations in the face of recurring mutations indicates that it is acted against by natural selection.
[5] Experiments by Sprague[23] have shown that ten to twenty plants are required for adequate representation of genetic diversity in an open-pollinated maize variety.
Since the number of ears saved for seed by ancient Asian maize cultivators with only small plots of land at their disposal was often smaller than this and, indeed, since new maize populations are sometimes established by growing the progeny of a single ear, it follows that there must often have been genetic drift – changes in gene frequencies resulting from the creation of small breeding populations.
[citation needed] A striking example of genetic drift in maize is the occurrence in parts of Asia of varieties with waxy endosperm.
More than 40 mutant alleles are known for the waxy locus, making up the finest collection of mutations found among higher plants.
[citation needed] Because the waxy mutation is expressed in an easy identifiable nonlethal phenotype, it has been the subject of major research during the 20th century.
[citation needed] Normal dent maize has two different pathways for starch formation one leading to branched chain (amylopectin) and the other to straight-chain polysaccharides (amylose).
Several researchers[36][50] demonstrated the presence in normal maize starch of about 5 to 7% intermediate polysaccharides, basing their conclusions on indirect evidence from IA.
The ratio of A-B chains (1:1 to 1,5:1) is a measure of the degree of multiple branching and is an important property describing amylopectin.
[citation needed] Amylopectin or waxy cornstarch is relatively easy to gelatinise, produces a clear viscous paste with a sticky or tacky surface.
[citation needed] Modified waxy maize starches are used for the improvement of uniformity, stability, and texture in various food products.
Waxy maize starch is also the preferred starting material for the production of maltodextrins because of improved water solubility after drying and greater solution stability and clarity.
[citation needed] Waxy corn on the cob is popular in China and Southeast Asia, and may be found in frozen or precooked forms in Chinatowns.
This waxy starch-based adhesive imparts resolubilizing resistance to the labels which prevents their soaking off the bottle if immersed in water or being subjected to very high humidity conditions.
[citation needed] Still the extensive (mushroomed) agro-research did not lead to any large scale use in the feed industry due to analytical research analysing the pancreatic digestibility of starches of several genotypes.
