Solanum Mauritianum Scop Research Articles

The effects of locality, season and year of seed collection on the germination of bugweed (Solanum mauritianum Scop.) seeds

The germination requirements of bugweed ( Solanum mauritianum ) seeds are highly variable and appear to be influenced by locality and season of collection. Generally, bugweed seeds do not exhibit primary dormancy, but as fruits are produced throughout the year most will be subjected to climatic conditions which make them conditionally dormant. Seeds collected from the Natal Midlands showed a higher frequency of conditional and secondary dormancy than seeds from the other three localities. Irrespective of locality, seeds tended to exhibit the greatest secondary dormancy when collected during warmer months. Many seeds will therefore escape pre- and post-emergent herbicide treatments which are normally applied during this time.

Biological control of silverleaf nightshade, Solanum elaegnifolium, and bugweed, Solanum mauritianum, (Solanaceae) in South Africa

The weed status and biological control of two introduced solanaceous plant species in South Africa are reviewed. Solanum elaeagnifolium Cav. (silverleaf nightshade, satansbos), indigenous to the southern USA, Mexico and Argentina, is a weed of arable and pastoral land. Mechanical adn herbicidal attempts at control have been largely unsuccessful. Faunistic surveys in the countries of origin of S. elaeagnifolium revealed at least 15 potential biocontrol agents, of which only a fruit-boring gelechiid moth, Frumenta nephelomicta (Meyrick), has so far been released, but failed to establish. Solanum mauritianum Scop. (bugweed, bugtree), indigenous to Argentina, Brazil and Uruguay, is a weed mainly of commercial forests in the high-rainfall areas of South Africa. The search for potential biocontrol agents has been hampered because the taxonomic status of S. mauritianum is unclear and only three insect species have been introduced into quarantine. Biocontrol of both Solanum weeds has been hindered by the oligophagous habits of the herbivorous species tested so far. The problem is compounded by the large number of agronomic species in the Solanaceae. In particular, Solanum melongena L. (eggplant) is acceptable to most solanaceous folivorous agents, at least under cage conditions, and only the more specialized, endophagous herbivore species may be suitable for introduction into South Africa. However, evidence is presented that the threat of folivorous agents to eggplant cultivations may have been overrated and prospects for the eventual release of these oligophagous agents are discussed.

Amino acid increases in fruit infested by fruit flies of the family Tephritidae

Solanum mauritianum Scop, (wild tobacco) fruit is the major host of the fruit fly Dacus cacuminatus (Hering), and is a major source of food for the brown pigeon Macropygia phasianella (Temminck) in eastern Queensland. Amino acid analyses were undertaken on fruit fly infested and uninfested S. mauritianum fruits. Infested fruits contained approximately twice the level of protein and essential amino acids compared to uninfested fruit. This increase is probably due to the plant adding additional amino acids to infested tissue and the accompanying growth of bacteria established in the fruit during oviposition. The infested fruit would provide a valuable source of protein during the pigeon breeding season.

Bacteria Associated with some Dacus Species (Diptera: Tephritidae) and their Host Fruit in Queensland

Over a period of 18 months the bacteria associated with approximately 70 adult flies of four Dacus species were isolated and identified. The flies were D. tryoni (Froggatt) and D. neohumeralis Hardy from guava (Psidium guajava L.), mulberry (Morus nigra L.) and peach [Prunus persica (L.) Batsch], D. cacuminatus (Hering) from wild tobacco (Solanum mauritianum Scop.), and D. musae (Tryon) from banana (Musa paradisiaca L.), and were collected in the field when these host plants were fruiting. All flies examined were surface-sterilized prior to aseptic dissection in which crop and mid-gut (stomach) or oesophageal bulbs were removed for culturing. Bacteria were also isolated from faeces of field-collected flies, as well as from host fruit surfaces, oviposition sites and larvae-infested tissue in host fruit. The predominant bacteria found in the alimentary tract of flies and in associated fruit specimens were members of the family Enterobacteriaceae. Klebsiella oxytoca, Erwinia herbicola and Enterobacter cloacae were the most frequently isolated species, with Serratia spp., Citrobacter jreundii, Proteus spp., Providencia rettgeri and Escherichia coli, being found less frequently. No one bacterial species was found to be consistently associated with anyone fly species. The bacterial species found most frequently in the alimentary tract were also found in large numbers on the surfaces of host fruit and in stung fruit.

Germination of seeds of Solanum mauritianum

Solanum mauritianum Scop. produces copious numbers of viable seed each year. These seeds are embryo dormant, require an after-ripening period, and will not germinate if incubated at constant temperatures. At alternating temperatures of 10 – 20 °C approximately 95% of these seeds germinate within four weeks. Gibberellic acid substitutes for this alternating temperature requirement and enabled the seeds to germinate at constant temperatures of 20, 25 and 30 °C. From the various imbibition experiments performed, it would appear that the seeds require a specific threshold level of GA 3 to stimulate the resumption of embryo growth. It remains to be established whether or not the temperature effect is tied up with the levels of endogenous gibberellins within these seeds.

Two New Species of Phytoseius Ribaga from Australia (Acarina: Phytoseiidae)

Females and males of 2 new phytoseiid mite species from New South Wales, Australia, are described and illustrated: Phytoseius leaki sp.n. from Solanum mauritianum Scop. and Phytoseius woolwichensis sp.n. from Eupatorium sp.