Genetically modified potato and cotton crops that express insecticidal proteins from Bacillus thuringiensis (Bt) have recently been commercialized. These crops display autonomous resistance to specific insect pests, and thus offer major agricultural and environmental benefits. We have implemented a microbial screening program to discover new types of insecticidal proteins for use in transgenic crops. New proteins with diverse modes of action offer opportunities to control insect pests that are not susceptible to Bt insecticidal proteins and to delay or prevent the potential occurrence of resistance of insects to crops genetically modified with Bt genes. Cholesterol oxidase emerged from our screen as a new insecticidal protein with potent activity against the cotton boll weevil. Cholesterol oxidase was acutely toxic to boll weevil larvae, with an LC50 of 2–6 parts per million when ingested in artificial diet feeding assays, and caused marked reductions in fecundity when ingested by adult boll weevils. Cholesterol oxidase also exerted significant, though less severe, toxicity against several lepidopteran pests. The insecticidal action of cholesterol oxidase appears to be due to oxidation of midgut epithelial membrane cholesterol followed by membrane disruption. A cholesterol oxidase gene was cloned and expressed in transgenic tobacco plants to yield plant tissue that exerted potent activity against boll weevil. Expression of this cholesterol oxidase gene in cotton plants may offer significant protection against the cotton boll weevil and may also aid in the mitigation of resistance of cotton lepidopteran pests to Bt proteins.
David R. Corbin, Frederick J. Perlak, David A. Fischhoff, John T. Greenplate, Zhen Shen and John P. Purcell
Wayne L. Schrader, Karen L. Robb and Valerie J. Mellano
The viability of urban interface agriculture (located near housing tracts, shopping centers, roadways, schools, and parks) depends on the ability of growers to allow their neighbors to enjoy the full benefits of their property. Growers must eliminate or minimize the noise, dust, flies, spray drift, odors, and field worker improprieties that can be associated with agricultural enterprises. An excellent way to minimize “ag/urban interface” problems is to grow a protective border planting between housing and agricultural production fields. Border plantings increase the aesthetic value of agricultural open spaces and screen out unwanted agricultural activities for those living adjacent to production areas. An ideal protective barrier planting consists of plants that 1) grow quickly and are easy to maintain; 2) provide a good physical barrier to dust, spray, and noise; 3) are inexpensive and aesthetically pleasing; 4) do not harbor insect pests that would damage crops or surrounding landscape plantings; and 5) support beneficial insects that prey on crop insect pests. Border planting sites were developed to identify plants that are adapted to border planting use and to gather information on insect populations that are supported by those plantings. Early results indicate that native plants including coyote bush, wild lilac, buckwheat, coffeeberry, yarrow, deer grass, and purple-needle grass can provide the desired physical barrier and beneficial insect support. Bio-diversity is the key to increasing populations of beneficial insects and several different native plant species have, therefore, been incorporated into the border plantings. Beneficial insect populations have been increased with appropriate border plantings.
D.S. Douches, W. Li, K. Zarka, J. Coombs, W. Pett, E. Grafius and T. El-Nasr
The potato tuber moth (Phthorimaea operculella Zeller) is the primary insect pest of cultivated potato (Solanum tuberosum L.) in tropical and subtropical regions, causing both foliar and tuber damage. In contrast, the Colorado potato beetle (Leptinotarsa decemlineata Say) is the most important insect pest in the northern potato production latitudes. The codon-modified Bacillus thuringiensis Bt-cry5 gene (revised nomenclature cry1IaI), specifically toxic to Lepidoptera and Coleoptera, was transformed into cultivar Spunta using an Agrobacterium vector to provide resistance to both potato tuber moth and Colorado potato beetle. The Bt-cry5 gene was placed downstream from the constitutive CaMV35S promoter. Two transgenic 'Spunta' clones, G2 and G3, produced high levels of mortality in first instars of potato tuber moth in detached-leaf bioassays (80% to 83% mortality), laboratory tuber tests (100% mortality), and field trials in Egypt (99% to 100% undamaged tubers). Reduced feeding by Colorado potato beetle first instars was also observed in detached-leaf bioassays (80% to 90% reduction). Field trials in the United States demonstrated that the horticultural performance of the two transgenic lines was comparable to 'Spunta'. These Bt-cry5 transgenic potato plants with high potato tuber moth resistance have value in integrated pest management programs.
Ruth S. Kobayashi, Stephen L. Sinden and John R. Stommel
Incorporation of genes from wild species has been a major contributor to tomato improvement in recent years. Solanum ochranthum, a woody non-tuber bearing species, is a potential source of resistance against tomato diseases and insect pests but is genetically isolated from tomato. Somatic hybridization methods were developed to facilitate the use of S. ochranthum for tomato germplasm improvement. Leaf mesophyll protoplasts of S. ochranthum and a Lycopersicon esculentum hybrid were chemically fused with polyethylene glycol. The protoplasts were initially cultured in Shepard's CL, a MS based medium, containing 1 mg·1-1 NAA, 0.5 mg·1-1 BAP and 0.5 mg·1-1 2,4-D. Hybrid regenerants and regenerants of the L. esculentum parent were recovered; S. ochranthum did not regenerate. Hybridity was established by morphological characters, peroxidase isozyme and RAPD markers. Use of these somatic hybrids for tomato improvement was evaluated.
Serudin Tinggal and Thean S. Tee
Magifera panjang Kostermans, indigenous to Brunei is widely adapted to lowland and hilly areas. The vigorous tree grows tall (30 - 40 metres high). Grafting on M. indica stock or own stock has dwarfing effect and shortens juvenile stage to stimulate fruit production within 5-6 years. The obicular fruits are large with tough brown skin. The thick golden yellow flesh is juicy, pleasant to eat, having aromatic fragrance. Some cultivars are less fibrous. The fruit has wide traditional usage and demand is seemingly unsatisfiable.
Mangifera pajang is quite tolerant to various diseases affecting mangoes. Insect pests do not appear to damage the trunk or the fruits.. The blossoms on stout and erect flowering spikes attract a host of pollinators. Anthracnose problem is unknown even in the wet season. These features are useful for possible transfer to the more susceptible M. indica cultivars.
In Integrated Pest Management (IPM), the costs of a control measure are compared to the potential for economic losses caused by a pest, with control measures being recommended only when expected costs of losses exceed costs of control. IPM models have been developed largely for insect pests, which multiply rapidly and for which timely population assessments are thus essential. Weed pests, on the other hand, multiply slowly. In the case of perennial crops, weeds may not reach populations sufficient to warrant control under conventional IPM criteria for many years. It is proposed that IPM concepts be adapted to weedy pests of perennial crops by creating models in which the long-term costs and consequences of both weeds and weed control measures are considered. These models would take into account expected increases in control costs and decreases in effectiveness of control measures over time and as a consequence consider some weeds to have effective thresholds at or near zero.
Han Yulin, Ha Huiquan, Xin Huipu, Zhao Pengxiang and Shi Xinwei
Stevia rebaudiana Bertoni was hydroponically raised on the matrices of sand or slag and sprinkled periodically with three different nutrient solutions (BD, KO, Knop) respectively. The conventional raising method of Hailin state farm was used as the control. The results showed that the seedlings grown on the matrix of sand and sprinkled with Knop nutrient solution were stronger with well-developed root systems, obvious spindle-shaped root tubers, and less plant diseases, no insect pests, and weeds, which was significantly better than the control method in respect to the root length, root fresh weight, stem height, shoot fresh weight, and number of leaves, and significantly better than other treatments in respect to the root length, root fresh weight and stem height. This raising method is worth extending.
Most farmers in Sub-Saharan Africa plant local cultivars introduced generations ago. Various national and international organizations and development projects introduce annually hundreds of improved germplasms to a country, and test these under farmer conditions for adaptability and acceptability. Although some local varieties perform well under traditional farming practices, many disease and insect pest resistant improved varieties out-yield local cultivars even under low-input production conditions of Africa. Regrettably, the seed production and distribution system in most of these countries are poorly developed; thus the promising varieties remain unavailable to the majority of farmers. To overcome this problem, the University of Arkansas-led Rwanda Farming Systems Research Project (FSRP) personnel trained farmer-cooperators in the production of good quality bean (Phaselous sp.) seeds. This, and the development of a farmer to farmer seed distribution system that led to quick diffusion of improved bean varieties in the project area will be discussed.
G.R. Brown, J. Hartman, R. Bessin, T. Jones and J. Strang
Apple growers would like to use pesticides efficiently and diminish concerns about food safety and pesticide usage. The 1992 Apple IPM Program objectives were: 1) to demonstrate the application of Integrated Pest Management practices in commercial orchards and, 2) to provide the training and support needed to help these growers become self sufficient in IPM practices. Grower training meetings and regular scouting of the orchards were the primary educational methods. End-of-the-season evaluations of past and disease incidence were made. Except for Frogeye Leaf Spot, there were no significant differences in insect pest, disease levels or in fruit quality attributes in IPM versus standard blocks. The IPM blocks had significantly more mite incidence. Growers did produce commercially acceptable crops using IPM based decisions while reducing the average past control cost by $56 par acre. Educational programs did help growers to be more proficient in making IPM based decisions.
R. L. Fery and P. D. Dukes
The Agricultural Research Service of the United States Department of Agriculture announced the release of `Bettergro Blackeye' southernpea on 24 July 1991. The new cultivar is well adapted for production throughout the southern United States where it can be expected to produce excellent yields of high quality, blackeye-type peas. `Bettergro Blackeye' outyielded the `Pinkeye Purple Hull-BVR' check in the 1986, 1987, 1988, and 1989 Regional Southernpea Cooperative Trials by 34.8, 14.3, 12.6, and 20.9%, respectively. Canned samples of fresh `Bettergro Blackeye' peas scored well in three years of quality evaluation tests. The new cultivar is resistant to the cowpea curculio, the major insect pest of the southernpea in southeastern production areas, and root knot, a severe root disease incited by several species of the root-knot nematode. `Bettergro Blackeye' plants have a greater tendency to produce a second crop than plants of most southernpea cultivars.