Strains of fluorescent pseudomonads increased the growth of tomato plants in nonsolarized soil but not in solarized soil. Vital staining showed that fluorescent pseudomonads colonize the root cortex and, apparently, internally colonize the younger lateral roots of artificially inoculated plants growing in nonsolarized soil. The minor pathogen Penicillium pinophilum caused growth retardation of tomato and cotton plants. It colonized tomato roots in nonsolarized, methyl bromide-fumigated, and solarized soils (to a much lesser extent). Inoculation of tomato roots with fluorescent pseudomonads or transplanting tomato roots to solarized soil suppressed colonization by Penicillium pinophilum and nullified plant-growth retardation. Inoculation of plant roots with plant growth-promoting strains of Pseudomonas putida, P. fluorescens, and P. alcaligenes reduced the incidence of disease caused by Sclerotium rolfsii in bean, Fusarium wilt in cotton and tomato, and reduced colonization of cotton roots by pathogens that cause these diseases. Induced suppressiveness against S. rolfsii in bean and Fusarium oxysporum f. sp. vasinfectum in cotton was observed in solarized soil. We suggest that fluorescent pseudomonads are effective agents in suppressing both major and minor pathogens in soil.

Non-Peer Reviewed | Crop loss studies were conducted in wheat and lentil near Delisle, Laird, and Vonda, Saskatchewan in 1991 and 1992. Wheat yield and biomass were reduced at one of four sites . Lentil yield was reduced at three of six sites; while lentil biomass was reduced at four of six sites. Wild tomato was most competitive when it emerged early and at high density, and when the crop vigour was low. In the fall of 1992, data were collected on the effect of wild tomato on harvestability. Wheat harvestability is not affected by wild tomato. Wild tomato caused soil to adhere to the lentil seed (earth-tag), and increased the moisture content of the lentil sample. Wild tomato berry juice mixed with harvest debris and this mixture plugged the concaves and the augers of the combine. Wild tomato seed is being spread by harvest equipment.

Intensive cultivation and monocropping of winter tomatoes in Malakand Agency (North West Frontier Province, Pakistan) have resulted in the occurrence of many destructive viral diseases which have caused tremendous losses both in yield and quality. Detailed and systematic work was conducted to determine the incidence, distribution, and losses due to viral diseases in Malakand Agency. An Average seedling infection of 30%, 15% and 20% of Tomato mosaic virus (TOMV), potato virus X (PVX) and potato virus Y (PVY) was recorded in tomato nurseries. Mean incidence of ToMV, Cucumber mosaic virus (CMV), Tomato yellow leaf curl virus (TYLCY), Tomato yellow top virus (TYTV), Tomato bushy stunt virus (TBSV), Tomato aspermy virus (TAV), Potato leaf roll virus (PRLV) and Tomato ring spot (ToRSV) virus on the basis of symptom expression and serodiagnosis, was 34.38, 12.92, 15.06, 8.26, 4.05, 1.48, 3.90 and 3.70 percent respectively. The predominant symptoms observed were mosaic, mottling, curling, bushy growth, shoe string, fern leaf, chlorosis, shoot proliferation and a variety of mixed symptoms. A reduction of 22.24% in fruit weight, 15.38% to 78.56% in fruit number and 25.77% in plant height was recorded, resulting in significant decrease in total yield.

Mixed instars of Thrips tabaci were allowed to feed on test seedlings of cucumber, the thrips were removed and wounds caused by thrips feeding dusted with tobacco streak virus (TSV) carried in tomato pollen. Transmission of TSV occurred in three out of the four experiments conducted. When Chenopodium amaranticolor test seedlings were dusted with infective tomato pollen, and thrips introduced for varying periods before being killed with insecticide, TSV transmission occurred after exposure to thrips for 1 h, 5 h, 1 day or 2 days, but not 5 min. Pollen‐washing experiments indicated that TSV was carried both internally and externally in pollen of tomato and several weed hosts. T. tabaci was able to transmit TSV from pollen of Nicotiana clevelandii and Nicandra physalodes, and TSV from tomato pollen was transmitted to several weed species. It is concluded that T. tabaci transmits TSV associated with tomato pollen by a mechanical mechanism whereby virus carried externally, or released from inside the pollen, infects feeding wounds.

The pathogenic effect of Trichoderma harzianum, T. viridae, T. pseudokoningii, T. aureoviridae, and T. glaucum on crops like rice, corn, pechay, tomato, and soybean was evaluated in the laboratory and greenhouse. Stunting and toppling down of affected seedlings caused by the Trichoderma spp. were observed on pechay and soybean but not on corn seedlings under the laboratory test. Under greenhouse test using sterile soil, pechay, and tomato seeds coated with T. harzianum and T. viridae, respectively, showed stem rotting. Stunting and yellowing of corn, tomato and pechay plants grown in soil with Trichoderma spp. were observed. On the other hand, improved growth was observed on soybean grown in soil with T. pseudokoningii and T. glaucum. Similar observation was noted on rice grown in soil with T. pseudokoningii

To determine which factors can affect biological expression of the Y satellite RNA of cucumber mosaic virus (CMV) in tomato, three laboratories collaboratively exchanged their natural satellite variants, the corresponding recombinant DNA clones and helper virus strains, as well as tomato varieties, on which different observations previously reported were based. The effects of these materials and the influence of temperature on symptom expression were systematically studied. The results show that in a standardized tomato bioassay at 24 degrees C, the Y satellite, when supported by either CMV-1 or CMV-Y, did not induce tomato necrosis in the Rutgers variety but elicited a slower necrotic response in the Best of All variety that was variably lethal, as compared to the faster inevitably lethal response induced by a prototype necrogenic D satellite variant in both tomato varieties. At higher temperatures (26.5 to 32 degrees C) an extremely fast-killing necrosis caused by CMV-Y itself was observed. The study demonstrates that in experiments on virus symptom modulation induced by CMV satellites, the nature of the helper virus, host plant varieties, as well as the environmental conditions should be precisely defined, and the effects of each parameter change determined separately.

The water potential, amount of pith autolysis and activities of apoplastic cellulase and polygalacturonase of tomato stems were measured during 24 h of drought stress (DS) and for 24 h following reirrigation. During DS the water potential dropped from -5.5 to -10.4 bars and rose to -8.3 bars soon after reirrigation. Drought stress induced considerable pith autolysis, more of which occurred after reirrigation. Pretreatment with mechanical perturbation (MP) of the stems or application of exogenous ethephon on the buds hardened the tomato plants against DS-induced pith autolysis. Drought stress caused an increase in apoplastic polygalacturonase and an even greater increase in apoplastic cellulase. Reirrigation caused a large transient increase in the former and a decrease in the latter. The apoplastic reducing sugar content (as galacturonic acid) of the stem rose in parallel with the activity of the enzymes. Both DS and MP caused an increase in ethylene evolution, although the former was significantly greater than the latter. However, when MP preceded DS, the amount of ethylene produced was significantly less than DS alone induced. Pretreatment with either MP or exogenous ethephon inhibited the increase in apoplastic cellulytic enzymes. It is concluded that DS induces ethylene evolution from the tomato stem, causing an increase in the stem apoplastic cellulytic enzymes, which in turn start the autolysis of the pith cell walls. Pretreatment with MP or ethephon, each of which induces ethylene evolution, hardens the stem so that it does not produce more ethylene during DS, and thus becomes resistant to DS-induced pith autolysis.

The economical meaning of pests on vegetable crops cultivated in greenhouses and plastic tunnels in Poland, have two spider mite species: Teranychus urticae Koch and T. cinnabarinus (Boisd.). Based on the injury they caused to leaves of cucumber and tomato, it was possible to identify both spider mite species. Some tomato varieties have been found to be more susceptible were the following cultivars: Corindo and Romato, but the least susceptible cultivar - Billy. In the experiments with chemical control of both spider mite species, the following compounds gave the best results: fenpyrad, acrinatrin, diefenthiuzon, abamectin and AC 303,630. The percent of mortality reached more than 98

During 1990, injury to tomatoes grown on the narrow land between the Albufera Lake (Spain) and the Mediterranean Sea was attributed to use of irrigation water coming from adjacent rice fields containing bensulfuron and quinclorac. A tomato root bioassay was developed to detect the herbicides in 10 ml of water. The assay was more sensitive to bensulfuron (0.5 ng ml-1) than quinclorac (100 ng ml-1). Only 30 ml of the affected water are necessary to conduct the test. Albufera water, sampled at three sites during 1991 and one during 1992 in the irrigation network canals caused different tomato main root length responses.