Quinoa is classified as a member of the Chenopodiaceae, a large and varied family with world-wide distribution which also includes cultivated spinach and sugar beet. The genus Chenopodium contains over 120 species, mostly colonizing weedy annuals and is distinguished from the rest of the Chenopodiaceae by a five-parted perianth enclosing small, incomplete but perfect flowers and the smooth to roughened or honeycombed surface of the seeds. Wilson, H. D. (1990) (Chenopodium sect. Chenopodium subsect. Cellulata) Econ. Bot. 44(supp.): 92-110; Barklay, T. M., Flora of the Great Plains University Press of Kansas, Lawrence, Kans.; 1986. Important Chenopodium weed species include C. album, which is widely distributed in Europe, Asia and North America; C. berlandieri, found throughout the western United States, and C. hircinum, which is sympatric with quinoa throughout much of its South American range. Wilson, 1990; Wilson, H. D. (1980) Syst. Bot. 5(3): 253-263; Wilson, H. D. and C. B. Heiser (1979) Amer. J. Bot. 66: 198-206. The latter two species have the same chromosome number as quinoa (2n=36) and have been demonstrated to hybridize artificially with it. Wilson, H. D. (1988) Syst. Bot. 13: 215-228; Wilson, 1980; Wilson, H. D. (1976) "A biosystemic study of the cultivated chenopods and related species" Ph.D. diss. Indiana Univ., Bloomington, Ind.; Gandarillas, H. and J. Luizaga (1967) Turrialba 17: 275-279.
Quinoa is an extremely hardy and drought resistant plant which can be grown under harsh ecological conditions--high altitudes, relatively poor soils, low rainfall and cold temperatures--that other major cereal grains, such as corn and wheat, cannot tolerate. Cusack, D. F. (1984) Ecologist 14: 21-31.
Although the seed of quinoa is not a true grain, but a fruit, quinoa is referred to as a pseudocereal because of its unusual composition and balance of oil, protein and fat. Quinoa's protein content is approximately 13.8% which is from 2-6% above most wheats and an even higher percentage when compared to other cereals like barley, corn, and rice. In addition, quinoa has an exceptionally high level of lysine, which is not commonly found in the vegetable kingdom, as well as high levels of phosphorus, calcium, iron, Vitamin E and B-complex vitamins. Cusack, 1984; Cardozo, A. and M. Tapia, "Valor nutritivo" pp.149-192 in M. E. Tapia (ed.) Quinoa y Kaniwa Cultivos Andinos Serie Libros y Materials Educativos No. 49 Instituto Interamericano de Ciencias Agricolas, Bogota, Columbia, 1979. Consequently, quinoa provides an excellent source of nutrition for humans and animals. Although no single food can supply all of the essential nutrients, quinoa comes as close as any other in the vegetable or animal kingdom. Furthermore, since the value of quinoa proteins is believed to be at least equal to that of milk, quinoa holds exceptional promise as a weaning food for infants, especially in nutritionally-deficient third world areas. Cusack, 1984.
Quinoa can be used in food in a variety of ways such as to make cereal, to make soup, to make flour which can be used to make paste, cookies or, when combined with wheat flour, high protein breads, and to make drinks. Quinoa has a slightly sweet, nutty flavor and can be eaten alone like rice. The leaves of the quinoa plant can be eaten in salads. In addition, to its nutritional value and drought resistance, the key non-nutritional advantages of quinoa as a human food source are quinoa's palatability, easy preparation and versatility. Cusack, 1984; James, L. (1991) "Sarah Ward finds grain is ticket to degrees and possibly new crop for U.S. agriculture" Fort Collins Business World June, 1991: 27-29.
Quinoa plants can be bred by both self-pollination and cross-pollination techniques but are predominantly an inbreeding species. Plants usually bear hermaphrodite flowers which are self-fertile. Natural pollination occurs in quinoa when the wind blows pollen from one plant to another or from one flower on the same plant to another flower on the same plant, or, more uncommonly for quinoa, when pollen is transferred by insects.
With self-pollinating plants, hybrid plant breeding is more difficult since the plants of two different varieties can fertilize themselves as well as each other. Thus, the resulting progeny are a mixture of the hybrid and the two parental varieties. One method to avoid a mixture of progeny is to render nonfunctional the male properties of one parent One such technique to create male sterile plants, especially in self-pollinating plants, is emasculation. Emasculation techniques vary greatly, depending upon the size of the anthers, the position within the flower, and the relative time of maturity between the anthers and stigma. Manual emasculation involves removal of anthers (the male reproductive organ) from a plant and is labor intensive. See Welsh, J. R., Fundamentals of Plant Genetics and Breeding, John Wiley & Sons, Inc., 1981.
However, a more advantageous technique to render the male properties of a self-pollinating plant nonfunctional employs cytoplasmic male sterile plants. Cytoplasmic male sterility (cms) provides a reliable and inexpensive means to emasculate a plant for hybrid production.
Well-characterized male sterile systems have already been used to breed hybrids in a number of crop species, including maize, sugar beet and onion. The use of such a sterility system can be cost-effective and labor conscious. In corn, for instance, the expensive and laborious task of detasselling is avoided when cytoplasmic male sterility is utilized to avoid self-pollinating. The use of the cytoplasmic male sterile system in a breeding program is also advantageous because of its simplicity and economy.
Cytoplasmic male sterility, a maternally inherited trait, is most widely used in the hybrid industry to render the male properties of a plant nonfunctional. This type of sterility affects only pollen production; seed set is normal. Generally, all the progeny from a male sterile plant are themselves male sterile. However, in some cases male fertility can be restored Pearson, O. H. (1981) Hort Sci. 16: 482-487. Fertility can be restored either by cytoplasmic reversion to fertility or by a nuclear restorer gene able to override the effects of cytoplasm. MacKenzie, S. A. et al. (1988) Proc. Natl. Acad. Sci. USA 85: 2714-2717.
Typically, upon identification of a source of cytoplasmic male sterility, the trait is transferred to a desirable "female" or "A" line. A "maintenance" or "B" line lacking both the sterility trait and restoration factor is used to perpetuate and increase the female line. A "restorer" or "R" line, carrying a pollen fertility factor is used as a male to pollinate the cytoplasmic male sterile "A" line to create a hybrid variety. The cytoplasmic male sterile plant of the "A" line can be crossed with a plant from a different variety to produce hybrid progeny. This type of breeding program is often referred to as a cytoplasmic male sterile-restorer system.
Quinoa has value as a field crop, particularly, in highland areas (having cold dry climates) around the world which are currently limited as to crop diversity and the nutritional value of crops. The development of hybrid varieties is one method for increasing crop production. Thus, it is important to plant breeders to develop stable cytoplasmic male sterile quinoa lines for purposes of producing, high-yield quinoa hybrids that are agronomically sound. By doing so, the goals to maximize the amount of grain produced on the land used and to supply food for both animals and humans can be attained.
However, hybridization techniques involving manual emasculation and pollen transfer are extremely difficult to perform on quinoa plants, as well as time-consuming and expensive due to the small size of the quinoa flowers and the large number of flowers in each inflorescence. Thus, breeders have searched for cytoplasmic male sterile quinoa lines for the production of quinoa hybrids.
Male sterile quinoa plants have been reported. In the late 1960's the existence of a male sterile plant with empty anthers was reported; however, the stability and inheritance of the character was not investigated. Rea, J. (1969) Turrialba 19: 91-96. Furthermore, Rea notes the presence of empty anthers that varied in color from whitish-yellow to pale brown. The color of anthers in quinoa plants having a gene for male sterility have been observed to be a whitish-yellow. The anthers of normal fertile quinoa are generally bright lemon yellow.
In the late 1960's two male sterile quinoa lines derived from Bolivian material were described. These lines produced a male fertile F.sub.1 generation when crossed with normal hermaphrodite pollen donors, and an F.sub.2 generation which segregated in the ratio 3 male fertile: 1 male sterile. Gandarillas, H. (1969) Turrialba, 19: 429-430. This type of segregation was ascribed to a single nuclear recessive gene controlling male sterility, i.e., genic male sterility not stable cytoplasmic male sterility. A third male sterile line (Line 650 of the Quinoa Germplasm collection in the Patacamaya Experimental Station) which produced all male sterile offspring when crossed and backcrossed to five different male fertile pollen parents was also described. In that instance, the male sterile character of those plants was considered, but never fully established, to be under cytoplasmic control. Gandarillas, 1969.
In the early 1970's, an unstable nuclear-gene-generated cytoplasmic sterility in quinoa of Bolivian origin was reported. Simmonds, N. W., Heredity 27: 73-82, 1971. Further, Risi and Galwey describe work by Aguilar, who reported cytoplasmic male sterility in the quinoa line UNTA 292. This line appeared to produce male sterile progeny in the F.sub.1 generation and on two successive backcrosses to male fertile pollen parents. Aguilar also reported that the cultivar Sajama apparently possesses a dominant nuclear gene which restores male fertility when combined with the cytoplasm of UNTA 292.
The development of male sterile quinoa lines to be used as the female parents in hybrid production has been suggested (Wilson, 1980; Risi, J. and N. W. Galwey (1984) Adv. Applied Biology 10: 145-216) but not yet reliably achieved. Hence, despite these potentially promising results, a reliable system of cytoplasmic male sterility in quinoa has not been reported, and cytoplasmic male sterile plants have not heretofor been available for commercial production of quinoa hybrids.