Plantes utiles du Kongo Central Province, République Démocratique du Congo

Les végétaux et leurs produits sont de la première importance pour la vie de la population rurale de l’Afrique. Localement, ils sont couramment utilisés pour la construction, la fabrication des outils, l’emballage, comme aliments et médicaments, pour nourrir le bétail et pour la protection des cultures et des terres. Aussi, les insectes comestibles constituant une part importante de l’alimentation dans une grande partie de l’Afrique, se nourrissent de certaines plantes. Les abeilles récoltent le nectar et le pollen pour produire le miel qui est très apprécié par la population et s’avère être une précieuse source de revenus dans la province. La connaissance des utilisations et même des noms locaux de nombreuses de ces plantes est entrain de se perdre. Cette publication fournit des informations recueillies localement, ainsi que de la littérature disponible, pour plus de 800 plantes poussant dans la province du Kongo central en République Démocratique du Congo. Le but de ce livre est d’encourager la plantation et la conservation des plantes au Kongo Central, province de la République Démocratique du Congo. La plupart des plantes citées sont également présentes dans plusieurs pays en région tropicale humide d’Afrique. Il est à espérer que ce livre sera utile aux fermiers, aux guérisseurs, aux étudiants et aux diverses catégories de personnes vivant en milieu rural. Le volume 1 couvre les espèces Abelmoschus esculentus à Leptaspis zeylanica. Le volume 2 contient Leptoderris congolensis à Zinnia angustifolia.

Performance of Selected Herbaceous Annual Ornamentals Grown at Decreasing Levels of Irrigation

This study was conducted to evaluate the growth, visual quality, and stress response of 17 species of bedding plants and Kentucky bluegrass (Poa pratensis L.) grown outdoors for 10 weeks during the summer of 2003 at three locations in Colorado. Plants were irrigated at 100% of the reference evapotranspiration (ET0) (amount required to maintain Kentucky bluegrass in an optimum condition) for 2 weeks followed by 8 weeks at five irrigation levels: 0%, 25%, 50%, 75%, and 100% ET0. Begonia carrieri Hort. `Vodka', Lobelia erinus L. `Cobalt Blue', and Viola ×wittrockiana Gams. `Crown Gold' grew well with a minimum of 50% or more ET0 based on Kentucky bluegrass. Impatiens walleriana Hook. fil. `Tempo White' grew well only with 100% ET0. Antirrhinum majus L. `Sonnet Yellow', Dianthus L. `First Love', Lobularia maritima (L.) Desv. `Carpet White', and Pelargonium ×hortorum L.H. Bailey performed well with 25% to 50% ET0. The species Catharanthus roseus (L.) G. Don `Peppermint Cooler', Rudbeckia hirta L. `Indian Summer', Senecio cineraria D.C. `Silver Dust', Tagetes erecta L. `Inca Yellow' and T. patula L. `Bonanza Gold', Zinnia angustifolia Kunth., and Salvia farinacea Benth. `Rhea Blue', which are adapted to midsummer heat and low water, performed well with 0% to 25% ET0. Species considered to be heat or drought tolerant—Petunia ×hybrida hort. ex. E. Vilm. `Merlin White' and Glandularia J.F. Gmel. `Imagination'—required little or no irrigation. The bedding plant species evaluated in this study that required 25% or less ET0 are well adapted for low-water landscape installations.

Herbaceous Plant Trial Results—1999

In 1999, LSU Agricultural Center landscape trials of herbaceous ornamental plants included zinnias, ornamental sweet potatoes, vinca, and perennial verbenas. Based on growth habit, flowering and disease observations from 1999 and previous years, `Homestead Purple', `Tiger Rose', `Rose King', `Taylortown Red', and `Blue Princess' (`Biloxi Blue') are recommended perennial verbena cultivars for Louisiana landscapes. Zinnias evaluated included Zinnia angustifolia and Z. elegans cultivars. `Crystal White', `Profusion Orange', and `Profusion Cherry' (all Z. angustifolia cultivars) were superior landscape performers. Major incidence of bacterial leaf spot was reported on all Z. elegans cultivars in 1999. Over the last several years, the Pacifica series of vinca had significantly improved visual quality ratings in landscape trials when compared to the Heat Wave and Cooler series. In 1999, Mediterranean Deep Rose had visual quality ratings similar to Pacifica but had increased incidence of disease problems. Ornamental sweet potato cultivars recommended for landscape use in Louisiana based on trials in 1999 are `Blackie', `Black Beauty', `Margarite', and `Pink Frost' (`Tricolor'). `Summer Frost' is not recommended.

Evaluation of Bedding Plant Varieties for Resistance to Phytophthora

Seedlings of several annual and perennial bedding plant species were inoculated with an isolate of Phytophthora nicotianae (synonym = P. parasitica) and planted into field beds in a simulated landscape situation. Throughout the growing season, growth measurements and disease ratings of the inoculated plants were compared with those of non-inoculated control plants of the same species in identical beds. Phytophthora-inoculated plants that continued to thrive through most of the growing season included Ageratum houstonianum, Celosia ‘Apricot Brandy’, and ‘New Look’; Dahlia ‘Harlequin’; Eustoma grandiflorum (prairie gentian); Lobularia ‘Carpet of Snow’; Nicotiana ‘Alta Dwarf White’, ‘Domino Salmon’, and ‘Nicki Red’; Pelargonium (geranium) ‘Multibloom Scarlet Eye’; Petunia ‘Polo Salmon’, and ‘Sugar Daddy’; Portulaca ‘Sundial Peppermint’; Rudbeckia ‘Rustic Dwarf’; Salvia ‘Lady in Red’, and ‘Victoria Blue’; Tagetes (marigold) ‘Disco Mix’, ‘Inca Orange’, ‘Inca Yellow’, ‘Janie Harmony Improved’, and ‘Gold Fireworks’; and Zinnia angustifolia. Plants that performed poorly following inoculation with Phytophthora include Antirrhinum (snapdragon) ‘Liberty White’, and ‘Liberty Mix’; Catharanthus (vinca) ‘Little Bright Eye’, and ‘Tropicana Rose’; Hibiscus ‘Disco Belle Mix’; Impatiens ‘Accent Bright Eye’; Leucanthemum x ‘Alaska’; Melampodium ‘Medallion’; Salvia ‘Turkestanica’; Torenia ‘Clown Mix’; Verbena ‘Imagination’; and Viola (pansy) ‘Fama See Me’. This study identifies bedding plant taxa which will provide an acceptable display in landscape beds infested with Phytopthora nicotianae (synonym = P. parasitica).

Responses of Zinnia angustifolia × Z. violacea Backcross Hybrids to Three Pathogens

True-breeding lines of Zinnia marylandica Spooner, Stimart & Boyle [allotetraploids of Z. angustifolia H.B.K. and Z. violacea Cav. (2n = 4x = 46)] were backcrossed with autotetraploid Z. angustifolia (2n = 4x = 44) and Z. violacea (2n = 4x = 48). Seed-generated, backcross (BC1) families were screened for resistance to alternaria blight (Alternaria zinniae Pape), bacterial leaf and flower spot [Xanthomonas campestris pv. zinniae (Hopkins and Dowson) Dye], and powdery mildew (Erysiphe cichoracearum DC. ex Merat). All BC1 families exhibited high levels of resistance to alternaria blight and powdery mildew. BC1 families derived from crossing Z. marylandica with autotetraploid Z. angustifolia were highly resistant to bacterial leaf and flower spot, whereas BC1 families derived from crossing Z. marylandica with autotetraploid Z. violacea were susceptible to this disease. Our results suggest that one Z. angustifolia genome in BC1 allotetraploids is sufficient to confer resistance to A. zinniae and E. cichoracearum, but at least two Z. angustifolia genomes are required in BC1 allotetraploids to provide resistance to X. campestris pv. zinniae.

Backcross Hybrids of Zinnia angustifolia and Z. violacea: Embryology, Morphology, and Fertility

True-breeding lines of Zinnia marylandica Spooner, Stimart and Boyle [allotetraploids of Z. angustifolia H.B.K. and Z. violacea Cav. (2n = 46)] were reciprocally backcrossed with diploid and autotetraploid forms of Z. angustifolia (2n =22 or 44) and Z. violacea (2n =24 or 48). In most cases, backcrosses were more successful with Z. angustifolia and Z. violacea as autotetraploids than as diploids. Seed-generated, backcross (BC1) families were obtained by crossing Z. marylandica (as female) with autotetraploid Z. angustifolia or autotetraploid Z. violacea. BC1 plants were phenotypically intermediate between the two parental lines for most morphological characters. Crosses between Z. marylandica and autotetraploid Z. angustifolia yielded BC1 plants with 33% stainable pollen, whereas crosses between Z. marylandica and autotetraploid Z. violacea yielded BC1 plants that produced malformed, poorly-stained pollen. No embryos were observed in capitula collected from field-grown BC1 plants. BC1 hybrids of Z. marylandica and autotetraploid Z. violacea produced larger capitula and more ray florets than Z. marylandica, and exhibited novel combinations of floral pigments not observed in Z. marylandica ray florets. BC1 hybrids of Z. marylandica and Z. violacea have commercial potential as seed-propagated, bedding plants.

PATHWAYS OF BACKCROSSING ZINNIA ANGUSTIFOLIA × Z. ELEGANS INTERSPECIFIC HYBRIDS TO THE PARENTAL SPECIES

Allotetraploid Z. angustifolia × Z. elegans hybrids (2 n =46) were reciprocally backcrossed to Z. angustifolia (2 n = 22 or 44) and Z. elegans (2 n = 24 or 48). Pollen germination and pollen tube penetration of the stigmatic surface were observed for all 8 cross combinations. At 14 days after pollination, the percentage of florets with embryos ranged from 0 to 69%, and some hybrid embryos exhibited developmental abnormalities. Seed-propagated backcross (BC1) populations were generated with Z. angustifolia (2 n =44)as ♀ or ♂, and Z. elegans (2 n =48) as ♀ BC1 progeny from these 3 crosses demonstrated low to high levels of resistance to bacterial leaf and flower spot (incited by Xanthomonas campestris pv. zinniae) and high levels of resistance to powdery mildew (incited by Erysiphe cichoracearum). BC1 hybrids derived from crossing allotetraploid hybrids as ♀ and Z. elegans (2 n =48) lines have commercial potential as disease-resistant, flowering annuals.