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Baldwin, B.S. 1996. Adaptation of kenaf to temperate climatic zones. p. 402-404. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Adaptation of Kenaf to Temperate Climatic Zones

Brian S. Baldwin

  1. MISSISSIPPI KENAF PROJECT
  2. DEVELOPMENT OF ADAPTED CULTIVARS
  3. PROSPECTS
  4. REFERENCES
Kenaf (Hibiscus cannabinus L., Malvaceae) is related to okra (Abelmoschus esculentus L.), cotton (Gossypium spp.) and Rose-of-Sharon (Hibiscus syriacus L.). Kenaf plants tend to grow as a single unbranched stem when planted at production densities (170-220,000 plants/ha). Stem color varies from pure green to deep burgundy. Flowers are borne singly, with five yellow petals and a red "blood spot" in the center of the flower. Leaves generally take two forms: deeply lobed and entire more or less resembling cotton leaves. The fiber is derived from the stem. Bast, or bark fibers are composed of phloem bundles and used extensively in cordage. The core, or woody fibers can be utilized in the production of paper, absorbants, animal bedding, and soilless potting media (Goforth and Fuller 1994).

Between the 1940s and 1960s, the feasibility of utilizing kenaf as a source of cellulose fiber for use in pulp and cordage was investigated by the USDA-ARS (White et al. 1970). It has been reported that whole stalk kenaf could be utilized in the production of paper (Nieschlag et al. 1960). However, pulping processes in the 1950s and 1960s as well as the availability of cheap wood caused interest in kenaf to wane. White and his group (1970) made an extensive investigation of the potential of growing kenaf in the southeastern United States as well as three mid-western states as far north as Nebraska. Of the 12 locations tested, only southern Florida was free of frost late enough in the year to provide viable seed for almost all of the varieties tested. Cultivars from Cuban (Cubano, C108, C2032), Floridian (E41 and E71), and Guatemalan (G4) ancestry were utilized because each showed some degree of resistance to anthracnose (Colletotrichum hibisci Polacci) (Wilson et al. 1965). Most kenaf cultivars are short-day plants. Dempsey (1975) reports that most improved kenaf cultivars remain vegetative until the daylight period falls below 12.5 h. Plantings of these cultivars north of 20deg. latitude results in strong vegetative growth, but induction of flowering occurs too close to the frost date for the production of viable seed. As a result, much of the seed planted in the United States is produced in Florida, south Texas, the Caribbean, and Latin America. Like its relatives, okra and cotton, kenaf attracts a number of pollinators to its flowers. Because of the moderate level of cross-pollination, seed obtained from tropical sources is frequently not true-to-type. This means that seed labelled as a single cultivar may contain plants with differing characteristics. Selections from these mixed seed lots and other germplasm has allowed researchers to develop lines that flower and set seed in Mississippi.

MISSISSIPPI KENAF PROJECT

The kenaf project was initiated in 1989 with the purchase and contract growth of several cultivars of seed for planting in the delta region of Mississippi. Survey of the literature indicated that the Cuban, Floridian, Guatemalan, and Taiwanese cultivars were probably best suited to Mississippi. Initial selections were made from several of these cultivars in 1993. Initial selection criteria was based solely on flowering date. Seven single plant selections were made from E71. In 1994, 0.20 ha plots were planted of G4, G45, G48, E41, E71, Cubano, C108, and C2032. Flowering date as well as Cristulariella pyramidalis Waterman & Marshall (a defoliating leaf spot) resistance were the selection criteria. Initial selections were crossed and selfed in the greenhouse and subsequent seed planted to the field the following spring. Germplasm was obtained from Charles Cook (USDA-ARS, Weslaco, TX) that were believed to be determinant. Somaclonal variants from Nancy Reichert's research (MSU/MAFES, Starkville, MS) were incorporated into the field nursery and observed for deviation from their parental lines. Additional selections were made from Indian and Russian germplasm. Crosses were made by utilizing the rooted meristems of the improved short-day types (that initiated flowering in the field) and germinated plants of the determinant types, or crossing rooted cuttings of a shorter short-day plant with a longer short-day plant. Agronomic potential of each selection and cross was evaluated when sufficient seed was generated. Evaluations were made based on plant height, plot yield, date of flowering and Cristulariella resistance.

DEVELOPMENT OF ADAPTED CULTIVARS

Currently, kenaf lines developed in Mississippi initiate flowers from the last week in June (May planting date) until frost. A study by Baldwin (1994) indicated that kenaf seed developing in north Mississippi needs 43-45 day after pollination to mature. With an average frost date of Nov. 7 (Starkville, MS), that study determined a target of Sept. 21-25 as the date of first open flower.

Our goal is not to be a major seed production center, but to have the ability to manipulate the genetics of the crop should the need arise. Cristulariella is a disease that strikes kenaf during humid summers. It defoliates the entire plant from 0.3 m below the apical meristem and remaining leaves are damaged by necrotic spotting. Cristulariella has been reported in North Carolina, Maryland, Alabama, (Pollack and Waterworth 1969), and Mississippi (Lawrence, MSU Plant Pathologist pers. commun.). The disease can be severe in the southeastern U.S., but typically is not a problem in the less humid western states. Southeastern growers cannot expect western breeders to select resistance for this disease. We must work with our own germplasm in this case.

Special interest is being paid to lines descended from determinant germplasm. The weather patterns of the Southeast and much of the Midwest result in heavy rains during the winter months. Frost-killed kenaf takes roughly 3-4 weeks to dry to 30% moisture (safe for harvest and storage). Therefore, the dependence on a killing frost to desiccate kenaf has meant that commercial production has had to stand in the fields until Mar. or Apr. Several selections from the determinant stock senesce and die as early as the last week in Sept., however, yield is severely compromised. Evaluations are now being made to find lines that senesce closer to the frost date, so that dry-down time will be decreased and fall harvest may be possible. Indeed, cultivars show differential rate of dry-down after kill. Investigations are under way to determine which cultivars reliably desiccate rapidly. Mississippi State University experimental lines MOP6 and MOP6E show the greatest promise for this, drying to 30% moisture 2-3 weeks before most other cultivars.

PROSPECTS

Variation existing in seedlots from kenaf production fields has allowed plant breeders to make selections for lines that are best adapted to each production region. Efforts in Mississippi have focused on successful seed set, disease resistance, and dry-down time to avoid winter rains and late harvest. Currently there are nearly 300 lines in the Mississippi program that flower and set seed at 33deg.N latitude. The best of these lines are being evaluated for yield and disease resistance at three locations in Mississippi. Release of germplasm and cultivars are expected in Spring 1997.

REFERENCES

Last update June 17, 1997 aw