Woody Core Fiber Length , Cellulose Percentage , and Yield Components of Kenaf w . C . Adamson

If kenaf lines differ in woody core fiber length and cellulose content, it may be possible to increase the pulp quality of kenaf through breeding. Forty-eight cultiYars, breeding lines, and accessions of cultivated kenaf (HibisCIlS camzabinus L.) were analyzed for diHerences in woody core fiber length and monethanolamine (MEA) cellulose, yield, and plant size. All commercial culth-ars of kenaf in the test had relatively short woody core fibers. In the breeding line with the longest woody core fibers, such fibers averaged 0.19 rom longer than those of the longest-fibered cultivar, a significant diHerence. Mean woody core fiber length showed negative correlations with yield, plant height, stalk diameter, and MEA cellulose. Kenaf lines and culth-ars did not vary greatly in MEA cellulose, and the commercial culth-ars were near the middle of the range. MEA cellulose showed positive correlations with stalk diameter and plant height. Additional index wOI'ds: Paper pulp source, New annual crop, Hibiscus cannabinus L. K ENA~ (Hibisclls c(lIlnabin./ls L.; has ~ong been cultivated for the productIOn .of bast £rber~..~e­ cent work in the U. S. has emphasIzed the possIbIlIty of using the entire kenaf stalk for preparation of paper pulp. However, research has concentrated on a vary few cultivars and these were selected primarily for bast fiber production and mechanical decortication (2, 4, 5, 6). Characters important in bast-fiber production may not be of primary importance in pulp production. Mechanical decortication, in particular, requires stalks with weak, brittle, woolly cores that can be easily broken up and separated from the bast 1 Contribution of the Sonlhern and North Central Regions. ARS. USDA. Receiyed l\lay 17. 1974. 'Research plant genelidsl. U.S. Plalll !tllroth.lction Slation, Savannah. GA 31405 and chemist, Northern RegIOnal Research Laboratory, Peoria, lL 61604, AGRO:\OMY JOUR:\AL, VOL 67, J-\:\U.-\RY-FEBRU.-\RY 1975 58 having significantly 'Everglades 41,' BG fibers, but a tougher, more dense woody fraction is more likely to yield better materials for papermaking. The purpose o! this work was to study a wide range of ken'll genetic material to determine what variation exists in two characters; a) woody core fiber length and b) total cellulose content, both of potential interest if kenaf is to be used for pulp production (6). If such variation exists, the relationship of the characters studied with productivity is of considerable importance. MATERIALS AND METHODS Forty-eight kenaf elltries, including breeding. lines, introductions. and cnltivars. were chosen as representauve of the range of morphological variation available in the U.S. collection of cultivated kenaI. Okra, A IiclllloscllIIs csclIlclltllS (L.) Moench, represented by 1'.1. 291124, was included for comparison ,dth kenaf because of the long ,\"{lody core fiber in this species (5). It would verify the effectiveness of the ,,'oody core fiber length test in the evellt that no variation "'as found in KenaI's fiber length. At the U.S. Plallt Introduction Station, Savannah, Ga., each of the 49 entries was planted Apr. 15, 1969 in a one-roll'. 3.7 Jll X 61 cm plot. The experimental design "'as a 7 X 7 lattice square with four replications. Before the kenaf was planted 45, 60, and 112 kg/ha of :\, 1', and K "'ere applied broadcast. Fifty-six days after the planting date, when plants ,,'ere approximately I m tall, 112 kg/ha of :\ "'as added. Seeds were hand-planted at the rate of about 100/plot. After the plants emerged, they "'ere thinned to a population level of about 99,000 plants/ha. Plants in a 1.5 m' area (2.46 Jll of ro,,') "'ere harvested in each plot on :\ov. 26 and 27, 1969 and dried at 60 C. Height of the standing plants was measured immediately before harvest. Stalk diameter ,"as measured on 10 dried plants from each plot. \Voody core fiber lengths were determined at the :\orthertl Regional Research Laboratory, Peoria, Ill. A sample of 4 to 6 plants, depending upon plant size, was taken from each plot. .-\ 10-cm segment was taken from the base and at a poim I m from the top of each plant. Bark "'as removed from these segments. The remaining ,,-oody core segments were quartered longitudinally. Then oue quarter from each section was sliced to increase surface area. These shavings were macerated in a hot acetic acid-sodium chlorite solution. Microscope slides of cellular material were prepared as described by :\ieschlag et al. (5), The mean ,,'oody core fiber length "'as determined for each sample by measuring 100 intact fiber cells from a ,lOX projection of each slide. Ten-plam samples were used in the determination of cellulose contem by a modified monoethanolamine (MEA) procedure (1). At Savannah. !In) 10-CIn samples were taken from each plallt in the same manner as described above, except that bark "'as not removed. The stalk sections '''ere rough-ground in a :\0. I \\'ile: mill and JeglOund through a 20-mesh screen in an intelmediate \\'ile\ mill. The ground samples were dried at 65 C in a laboratorv oven and allov,'eel to equilibrate in the laboratory before they' ,,'ere weighed. 1''''0 g ,,'ere ,,'eighed from each sample and placed on a 12.7 cm sCjuare of heavy cotton cloth. The cloth was then doubled over diagonally and sewed around the edges with cotton thread: this operation produced a triangular cloth bag "ith the sample inside. Sam pIes "'ere identified by graphite pencil markings directly on the bags. Each replication of 49 ell tries was cooked ill 5.5 liters of MEA for 3 hours at 170 C in a cast aluminum, metal-to-Illctal sealing, pressure cookcr fitted ,,'ith two condensers. All samples "'CIT "'ashed thoroughly, dried at 65 C, and allowed to equilibratc in the laboratory. The samples were removed frolll the cloth bag by cutling ai'ound the seam ,dlh scissors. Each sample was ,,·eighed. and its per ccnt residue "'as recorded. In 1970 ten cntries, including lines idelltified as having long \modv fibers in 1969, wcre established ill single-rc)\,' plots at Savatlnah. Rows and plants within J'(l\\'S were 6t cm apart. Ten individual plallts from each cntry "'cre sampled, and fiber length determinatiollS "'ere IlJade at Peoria as previously dcscribed. In 1971 at Savallnah a Ilursery "'as established containing I3G 52-1:35 and j-I-1I3-1, identified as having long '\'Clody core fiber, along "'ith Ilormal kenaf cultivars. and scveral F, populations of crosses bet"'een cultivated types and the two longfibered lilles. Ro,,'s "'cre 66 cm apart. and plants within rows "'CIT 30,:) cm apart. PI,lllts "'erc samplcd and tested as previonsly described. Testing '''as discontinued when no difference in "'oody core fiber length "'as found aillong previously tested lincs. Data frotn the 1969 and 1970 tests "'CIT analyzed according to Inethods given by Cochran and Cox (3). RESULTS AND DISCUSSION 'Woody Core Fiber Length Mean woody core fiber length among kenaf entrie~ in the 1969 test varied from 0.78 mm for BG 52-135 to 0.51 mm for A60-278 (Table I). All commercial cultivars had relativelv shan woody core fibers. Several entries had sio'niricantlv lonoer' woody core fibers b .. b • than any of the commercial cultivars tested. Okra represented by P.I. 291124, produced longer wooely core fibers than any kenaf en tn. \Vooely core fiber length showed signi'ficant but sl;lall negative correlations with yield anc! with plant height and stalk diameter, and a larger negative correlation with I\JEA cell ulose (Table 2). Of the seven kenaf entries longer woody core fiber than Table 1. Variation among Kenaf (Hibiscus camzabilllts L.) entries in five measured characters in 1969. Entry· Source Woody fiber length ?-lEA cellulose Yield Plant height Stalk dia,