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  • Author or Editor: Lurline Marsh x
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Four cowpea [Vigna unguiculata (L). Walp] genotypes; IT 82E-18, IT 82E-16, Pinkeye Purple Hull, and Coronet were tested for somatic embryo formation and embryogenesis. Explants were 3-week-old cotyledons from which the embryonic axes were removed. Cotyledons were cultured in eight media combinations representing modifications of two media, one containing Murashige and Skoog Basal salt with B5 vitamins (MSB), 500 mg/L casein-hydrolysate (CS), 500 mg/L sodium chloride, 3% sucrose, 0.7% agar, 2mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/L benzylamino purine, and the other containing (MSB), 3% sucrose, 40 mg/L 2-4-D and 0.2% gellan gum. After 1 month, 40% to 100% of explants produced calli and few produced shoots. Subcultured shoots in MS with 0.1 mg/L indole-3-butyric acid (IBA) or with IBA and 0.5mg/L kinetin (KT) failed to produced roots. The only green cotyledonary stage embryo was produced on this latter medium. Subculture of calli in MSB containing CS, mannitol, sucrose, agar, indoleacetic acid, and KT produced cream-colored globular embryos, roots, and a few leaves.

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The effect of moisture content on the emergence and development of `Pinkeye Purple Hull' and MN 13 cowpea [Vigna unguiculata (L.) Walp.] and `Clemson Spineless' okra [Abelmoschus esculentus (L.) Moench] seeds was investigated in a 3-year field study. Moisture content, ranging from 8% to 52%, was obtained by combining seeds, vermiculite, and varying volumes of water in sealed polyethylene packets and incubating them at 22C for 3 days. High moisture promoted the emergence of MN 13, did not significantly affect that of `Pinkeye Purple Hull', and decreased that of `Clemson Spineless' seeds. Percent seed emergence 22 days after planting averaged 17 % for `Clemson Spineless' and 15% for `Pinkeye Purple Hull' seeds, but was 44% for MN 13. High moisture generally promoted early harvest of MN 13 and increased root dry weight but did not affect fresh-pod yield significantly.

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Thirty-seven okra (Abelmoschus esculentus) plant introductions and 3 cultivars, `Clemson Spineless', `Clemson Spineless 80', and `Candelabra Branching' were evaluated for their fruiting characteristics during a three year field study. Harvesting at 3 to 4 day intervals produced inmature fruits which were approximately 4 to 7 days old. These immature fruits when graded according to fruit length, were primarily very small (<4.4 cm) or small (4.4-8.9 cm). There were few medium (>8.9 cm but <12.7) or large (>12.7 cm) fruits. Of the 40 genotypes, Clemson Spineless averaged 46 pods per plant over 17 harvests. Few other plant introductions were comparable in the number of pods produced. Except for one, all other genotypes produced predominantly green fruits. Many of the genotypes were early maturing.

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Seedling emergence and growth of 39 genotypes of okra [Abelmoschus esculentus (L.) Moench] were studied at several temperatures. Seeds were evaluated in two separate studies. One was a 3-year early planting field evaluation where air temperatures ranged from -2 to 29C. The other was a study at controlled temperatures of 10/10, 14/10, 15/15, 20/10, and 20/20C day/night. Okra genotypes showed variation in seedling emergence in the field, but the results fluctuated over years. Seedlings emerged at all the controlled temperatures, although the percentage of emergence reached only 13% at 10/10C. All temperature regimes produced some degree of leaf chlorosis, the severity of which was greatest at the lower temperatures. Leaves of none of the okra seedlings of any of the genotypes grew at 10/10, 14/10, or 15/15C. Genotypic variation in emergence was observed with the controlled temperatures.

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Explants (cotyledon, cotyledonary node, second node, hypocotyl, epicotyl, and leaf) of cowpea (Vigna unguiculata) genotypes MN13 and Pinkeye Purple Hull were cultured on Murashige and Skoog basal nutrient medium. The medium was supplemented with 1 mg·L–1 benzyladenine (BA) or 1 mg·L–1 benzyladenine plus naphthalene acetic acid (BA + NAA) or 2 mg·L–1 2,4-dichlorophenoxy acetic acid (2,4-D). Cultures were maintained at 22°C for 1 month, after which they were transferred to 1 mg·L–1 BA + NAA. Cotyledons, hypocotyl, epicotyl, and leaf segments produced only calli after subculturing in BA + NAA. The second node and cotyledonary node explants cultured on the BA or BA + NAA followed by subculture on BA + NAA produced calli, shoots, and roots. The plants were then transplanted to promix but later died.

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Determinate, photoperiod-insensitive genotypes of pigeonpea [Cajanus cajan (L.) Millsp.] have production potential for the short growing seasons of the temperate region. A 3-year field study was conducted to determine the effect of three planting dates on the growth and development of pigeonpea in Missouri. Seeds of four genotypes, ICPL 87 Isolation (85k), ICPL 85010, ICPL 85024, and ICPL 8304 were planted 1 May (PD1), 15 May (PD2), and 1 June (PD3). Germination of the earliest-planted seeds was <32%, but increased to an average of 57% for PD3. Earliest-planted seeds generally took the longest time to first flowering and harvest. The initial fresh pod harvest of plants from PD1 and PD2 overlapped. The earliest harvest was produced by ICPL 85024 from PD2 at 91 days (1300 degree-days C) after planting. Over the 3 years, the genotypes in PD1 produced the highest fresh pod weights (205-357 g/plant) and longest pods. Those of PD3 produced the lowest pod weight. The seed number per pod (three to four) and weight of 100 seeds (16-22 g) were generally unaffected by planting dates.

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The floral abscission patterns of five early maturing pigeonpea genotypes; ICPL 146 1985HK, ICPL 87 Isotation (85K), ICPL 85010, ICPL 85024 and ICPL 8304 were studied on field grown plants in Missouri. Individual plants were bagged with nylon nets at the beginning of flowering, and the buds, flowers and pods were collected weekly and counted. Abscission began after anthesis and was excessive throughout most of the flowering period. The number of open flowers which abscised was much greater than that of buds or immature pods. The maximum number of weekly abscission of flowers per plant was 470 for ICPL 146 1985HK. Low night temperature below 10°C enhanced abscission of buds, flowers and immature pods in pigeonpea.

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Somatic embryogenesis can be used to facilitate the improvement of traits in plants. The study was conducted to assess different ages of immature zygotic cowpea (Vigna unguiculata (L. Walp), “MN13” cotyledons for their ability to produce somatic embryos. Cotyledons were harvested weekly for the first 8 weeks following anthesis. After removal of their embryo axes, they were cultured in Murashige and Skoog (MS) medium containing 0.6% agar, B-5 vitamins, 3% sucrose, and 20 mg·L-1 2,4-dichlorophenoxy acetic acid (2-4D). Cotyledon explants of all the ages produced calli. The percentage of explants producing calli ranged from 32% to 92%. On transfer of the calli to similar medium containing 0.2% gellan gum instead of 0.6% agar, all ages except those from the 1-week cotyledons produced white globular somatic embryos. The largest of these embryos were 9 mm in length. The highest frequency of globular embryos was produced with the 3- to 5-week-old cotyledons.

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Determinate, photoperiod-insensitive genotypes of pigeonpea, (Cajanus cajan) have the potential for production in the short growing season of the temperature region. A field study was conducted to determine the effect of three planting dates on the growth and development of this crop in Missouri. Seeds of four genotypes, ICPL 87 Isolation (85k), ICPL 85010, ICPL 85024 and ICPL 8304 were planted at three planting dates in 1990, May 1, May 15 and May 31. Germination of the earliest planted seeds was low but increased in the later planted ones. The earlier the planting date the longer was the time to flowering, but the earlier was pod maturity. The earliest planted group flowered within 78-110 days after planting. The genotypes in this group produced the highest fresh pod weights of 330-730 g/plant and the latest planted ones produced the least. Pod length, the number of seeds per pod and weight of 100 seeds had ranges of 5.1-5.9 cm, 3-4 seeds and 17-23 g, respectively and were unaffected by planting dates.

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Tissue culture of four cowpea (Vigna unguiculata) and two pigeonpea (Cajanus cajan) genotypes was tested on Blaydes' medium supplemented with different hormone concentrations. Explants of cotyledonary nodes, cotyledons and leaves of the cowpea genotype IT82E-16, IT64E-124, Pinkeye Purple Hull and MN13 produced callus after 4 weeks in Blaydes' medium. The hormone combinations in the medium were 2-l dichlorophenoxy acetic acid (2.4-D) (2 mg/liter) and kinetin at 0.05, 0.1, 0.5 mg/liter, or 2,4-D and thidiazuron (TDZ) at 2.2, 4.4 and 6.6 mg/liter or benzylaminopurine (BA) at 2.25, 4.5 or 6.75 mg/liter. Shoots occured on cotyledonary nodes of Pinkeye Purple Hull In the TDZ (6.6 mg/liter). Roots were produced from the leaf and cotyledonary nodes of Pinkeye Purple Hull and on cotyledons of IT-64E-124 cultured In media with kinetin (0.5 mg/liter). Leaf and cotyledon explants of pigeonpea genotype; ICPL 146 1965HK and ICPL 65024 produced callus and some shoots in BA (2.25 mg/liter) after 4 weeks. The callus when subcultured on BA (0.5 mg/liter) and NAA (0.1 mg/liter) produced shoots. Regenerated shoots rooted in the Blaydes' medium with kinetin (0.01 mg/liter) and NAA (0.6 mg/liter).

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