Oawid R. Johnson and James A. Percich University of Minnesota, St. Paul

Wild Rice Domestication, Fungal Brown Spot Disease, and the Future of Commercial Production in Minnesota

Wild rice (Zizania polusiris L.) is an over 8,000 ha in 10 counties (Fig. 3). separate genus. The remaining two aquatic grass native to North America. Current production techniques and wild species, 2. aquarica L. and Z. palusrris, Its edible seeds are similar in size and rice cultivars were developed by Minne- are indigenous to lakes and rivers of shape to those of white sice (Oryzasoriva sota growers in cooperation with the Uni- eastern and north central North America, L.). but wild rice is not closely related versity of Minnesota within the last 40 and grains harvested from natural stands to Oryza spp, or to southern wild rice years. have been utilized as a food source for (Zizaniopsis rniliacea (Michx.) DSll & The industry flourished throughout centuries (7). The two species recently Aschers). The unusual innoresence of most of its history but is now threatened. were subdivided into botanical varieties wild rice prevents self-pollination be- Recently, fungal brown spot (FBS), based on grain morphology and isozyme cause female florets are produced on the caused by Bipolaris oryzae (Breda de distinctions (1,8) (Table 1). Some wild upper part of the panicle and are no Aaan) Shoemaker (Fig. 4A). the ana- rice harvested from natural stands is 2. longer receptive when the male florets morph of Cochlioholus rniyabeanus (It0 oquatico, hut the majority is k palusfris. emerge below (Fig. I). The harvested & Kuribayashi in lto) Drechs. ex Dastur, Only 2. pafusrris var. interior is grown grain of wild rice is highly prized as a and B. sorakiniana (Sacc.) Shoemaker in inaens~velymanaged paddies. gourmet item because of its unique tex- (Fig. 48), the anamorph of C. sarivus ture and nutty flavor. Sclerotia of ergot (lzo & Kuribayashi) DF~-chs.ex Dastur, Erolutlon of the Commercial (Clavireps zizaniae (Fyfes) Pantidou) has become the limiting Cacter in pro- WHd Rice Industry have also been cotlected and sold as a duction. Although FBS has been a prob- 'The first commercial field af wild rice source of alkaloids. lem since the inception of commercial was planted in 1950 near Merrifield, Before commercial production began, production, recent changes in pesticide Minnesota, using seed from natural stands. wild rice was difficult to obtain and labeling have almost eliminated options After one successful season. thc second always commanded a high price. It was for chemical control. Market cornpeti- crop in this field was destroyed by FBS painstakingly hand-harvested from witd tion from growers in regions where FRS (14). In the next decade, FBS destroyed stands by Native Americans and a few is not a problem has driven down the many other wild rice crops, including a licensed "ricers," who flailed ripened price of wild rice. while production costs 10-ha stand planted by a large Trozen- grain into their canoes with wooden for Minnesota growers have increased. food company. Hope for quickly ebiain- sticks (Fig. 2). The advent of commercial Thus, the commercial wild rice industry ing resistance through simple selection wild rice production has made this seems likely to diminish in the state where vanished when surveys of numerous in- practice largely unprofitabte, but it it was born. lo this paper we review the fected wild rice stands revealed no varia- continues on a small scale. Most wild history of commercial wild rice produc- tion for reaction to FB5 (1 3). rice in Minnesota is now mechanically tion and discuss factors that have made Commercial wild rice production is harvested from intensively managed FBS a serious threat to the industry in hindered by "shattering," the progressive paddies. Commercial production has Minnesota. loss of ripened grain from the panicle begun in many parts ofthe United States following uneven maturation. In 1963, and Canada, and the California industry f axonomy University of Minnesota agronomisls now rivaEs that of Minnesota. Wild sice The common name "wild sice" has discovered a few shatter-resistant wild is still considered a gourmet item, but historically been applied to four different rice phenotypes in one commercial field it is no longer scarce or expensive. aquatic grasses in the: genus Zizanio, that had a significant yield advantage Minnesota and the surrounding Great three of which are native to North over the more shatter-prone phenotypes Lakes region is the center of origin for America. Texas wild rice (2, rexana despite their susceptibility to FBS. All wild rice. It is the only cereal native Eo Hitch.) is a short-statured perennial subsequent commercial cultivars were North America that has been dornesti- found only in a restricted area of the San derived from these selections of 2. cated from a wild plant. Commercial Marcos River in Texas. The grain of this palustris. Some losses to shattering still production of wild rice originated in wild rice is smaIl and not exlensivety occur because cornmerciaI cultivars are Minnesota, where it is now grown on harvested by man. Manchurian wild rice actuatly mixtures with varying degrees (Z. latfolia (Griesb.) Turcz. ex Stapf.) of shatter resistance. Published as paper No. 18.979 or the contribution is a perennial native of Asia. The grain Shatter-resistant cultivars and improved series of thc Minnesota Agricultural Ekpesimcnr of this species is not harvested, but the production techniques allowed the in- Srarron based on re-arch conducrtd under Project 22-68. lower stems are used as a vegetable when dustry to prosper and grow. In 1968, only infected by the smut fungus UsziIago 365 ha of wild rice were planted in Min- Dr. Johnson's ddrtss is University of Minnesota. esculenra Henn. (28). Manchurian wild nesota, but by 1978, 4,860 ha produced Dcpaflmenr of Agronomy and Plant Genttics. dl 1 rice differs from the three North Amer- 1.09 X 10' kg of processed wild rice. In Rorlaug Hall. 1991 Bulard Circle. SI. Paul, MN 55 108 ican species in genera! morphology and 1986, a record 2.32 X 10' kg were pro- chromosome number (2n=34vs. 2n=30) duced on 10,125 ha. Total annual pro- @ 1992 The American PhytopathologlcalSociety and perhaps should be placed in a duction was lower from 1987 through Plant Disease/December 1992 1193