A pathogenic strain of Xanthomonas campestris pv. vesicatoria, causal agent of bacterial spot of tomato (Lycopersicon esculentum Mill.), was genetically engineered to bioluminesce. In planta growth of the bioluminescent strain was similar to that of its parental strain. Movement and growth of the bioluminescent strain in susceptible tomato seedlings after wound inoculation was followed over time with a liquid-N-cooled, charge-coupled device camera. Highly significant differences in bioluminescent bacterial growth were observed in the four tomato cultivars used. Systemic bacterial movement was most pronounced in `Sunny', which showed population development not only at the inoculation sites but also on several sites in the leaves and at the leaf margins. Bacterial bioluminescence levels in `Campbell 28' remained significantly lower than those observed in `Walter' and `Sunny'. The technique offers unique possibilities for studying host-pathogen interactions and bacterial pathogenesis.
The peach breeding program in Louisiana was initiated in the late 1940's to develop adapted cultivars for Louisiana. The objectives of the program have been to develop large fruited disease resistant fresh market cultivars for all areas of Louisiana. The state is divided into three climatic zones in reference to the breeding program (north, south, and coastal). Cultivars have been developed that are adapted specifically for each zone. A few cultivars produce marketable fruit in all three zones. The annual chill units vary from 350 to 1000+ over the three zones. Seventeen cultivars have been released since 1969 and these are used throughout the southeast U.S. in production areas. A primary breeding objective is to develop a sequence of cultivars to service the market from late April through September. Also equally important is development of genetic disease resistance to bacterial spot, Xanthamonas campestris pv pruni.
`White Rock' and `White County' fresh market peaches (Prunus persica (L.) Batsch) were released in 2004 by the University of Arkansas Agricultural Experiment Station. These cultivars join `White River' as recent products of the peach breeding program which is based at the University of Arkansas Fruit Substation, Clarksville. Both cultivars are sub- or low-acid types and have white flesh. `White Rock' ripens at on average 25 June, and is very firm at maturity. Average fruit weight was 142 g with 12% soluble solids and light white peach flavor. `White County' ripens on average 14 July. It is large fruited with average weight of 258 g and maintains firmness until full maturity. The fruits are freestone with an excellent white peach flavor. Both cultivars show good bacterial spot resistance although occasional lesions are seen on leaves. These new cultivars offer additional white peach cultivar choices for the mid-South and other areas of similar climate.
Hungavit® products contain extracts of earthworm castings and are marketed by BioLife Ltd. as liquid Bio-leaf fertilizer and plant conditioner. Three experimental plots were set up on the AAFC-SCPFRC research farm to evaluate Hungavit®UR, Hungavit®P, and a preparation containing the equivalent amount of N, P, K fertilizer. In Spring 1998, four replicate plots/treatment of tomato, pepper, and potato were set up in a randomized block design. Each plot received the following treatments: untreated control, Hungavit®UR for tomato and pepper or Hungavit®P for potato, and the fertilizer equivalent of Hungavit®UR or P without the organic components. Tomato and pepper plants were treated three times by foliar application at the rate of 5 L/ha using 300 L of water/ha carrier. Leaf chlorophyll contents were measured at 2, 4, and 6 weeks after initial treatment application. Early and total yield were determined. Tomato fruit were evaluated for symptoms of bacterial spot, early blight, anthracnose, and blossom end rot; pepper fruit for bacterial spot; and potato tubers for potato scab. Both Hungavit® and its equivalent fertilizer application increased the chlorophyll readings significantly in at least one measurement for tomato, pepper, and potato plants. Although there were 40% to 55% fewer diseased tomato and pepper fruit in fertilizer and Hungavit® UR treatments, this was not statistically significant from the control treatments. Fertilizer treatment also reduced scab incidence in tubers by 50%, but the overall scab level was very low even in untreated plots. Hungavit® and its fertilizer equivalent had no significant effect on the early or total yield of tomato, pepper, or potato plants.
‘Harcrest’ is a cold hardy, productive, attractive, firm-fleshed freestone peach [Prunus persica (L.) Batsch] that ripens 2-3 days after ‘Cresthaven’ and ‘Redskin’ in the late season. It was introduced in 1983 for the Ontario fresh market to extend the ‘Cresthaven’ and ‘Redskin’ season with a similar type of peach and is considered a potential replacement for ‘Redskin’. The tree is vigorous and appears to have moderate field tolerance to perennial canker (Leucostoma spp.). Leaves and fruit are moderately resistant to bacterial spot [Xanthomonas campestris pv. pruni (Smith) Young et al.] while flowers and fruit are resistant to brown rot [Monilinia fructicola (Wint.) Honey]. Fruit are resistant to split pits but subject to preharvest drop if hot, dry conditions prevail just before harvest. The yellow flesh does not brown readily on exposure to air. ‘Harcrest’ is well suited for the fresh market including local sales and shipping and is suitable for preservation at home by canning or freezing. ‘Harcrest’ is performing well in regional trials in Ontario, and is adapted to regions where ‘Redhaven’ is successfully grown.
‘Harson’ is an attractive, high-quality, yellow-fleshed, freestone peach [Prunus persica (L.) Batsch] that ripens in the midseason 2 days before ‘Redhaven’. It was introduced in 1982 for the Ontario fresh market to advance the season of ‘Redhaven’-type peaches by 2 days and reduce the gap in harvest sequence between ‘Sunhaven’ and ‘Redhaven’. The tree is of medium vigor, cold hardy, productive, and appears to have moderate field tolerance to perennial canker (Leucostoma spp.). The fruit appear to be resistant to bacterial spot [Xanthomonas pruni (E. F. Sm.) Dows.], brown rot [Monilinia fructicola (Wint.) Honey], split pits, preharvest drop, and flesh oxidation. They are wellsuited for the fresh market, including local sales and shipping, and for preservation at home, especially as canned halves and frozen slices. Research and grower cooperators in southern Ontario and near Annapolis Royal, Nova Scotia report that ‘Harson’ is performing well in their trials compared with other midseason cultivars and encouraged its introduction. This new cultivar is likely to be adapted to most regions where ‘Redhaven’ is grown successfully. The name ‘Harson’ honors T.B. Harrison for his many years of service to the Western Ontario Fruit Testing Association and the fruit industry of Ontario.
The effects of replanting stand-deficient plots on marketable tomato (Lycopersicon esculentum Mill.) fruit size and yields were investigated at Bradenton, Fla. during the 1986 spring and fall seasons. Treatments consisted of a control (10-plant plot) and plots with 9, 8, and 7 (10%, 20%, and 30%) missing plants. Other plots with the same stand deficiency were replanted to attain a complete stand 2 or 3 weeks and 1, 2, or 3 weeks after initial transplanting in the spring and fall experiments, respectively. Plots with 30% stand reduction produced a lower weight and number of marketable fruit per hectare than control plots in both seasons. In spring, replanting stand-deficient plots did not increase marketable fruit yields relative to plots not replanted, regardless of the time of replanting or percentage of stand reduction. In fall, under an unfavorable environment due to a late infestation of bacterial spot, replanting plots with 30% stand reduction increased marketable fruit yields over similar plots that were not replanted, when the replanting occurred 1 or 2 weeks after initial transplanting, but not when replanting was delayed 3 weeks. Small, medium, or extra-large marketable fruit weight per hectare were similar in both seasons for plots with 30% stand reduction, whether replanted or not. Mean fruit size (g/fruit) did not differ significantly among treatments in either experiment. These results suggest that replanting improved marketable tomato yields only when the level of stand deficiency reached 30% and only in a stressed environment.
Four greenhouse leaf inoculation methods for screening Japanese plum (Prunus salicina L. and hybrids) for resistance to Xanthomonas campestris pv. pruni (Smith) Dye were compared for repeatability, ability to differentiate among plant genotype responses, and correlations with field ratings. Clonally propagated trees were inoculated artificially in a greenhouse by immersing leaves in 2.5 × 108 cfu/ml inoculum (DIP), rubbing the adaxial side of leaves with a slurry of 2.5 × 108 cfu/ml inoculum and Carborundum powder (CARB), infiltrating leaves with 5 × 105 cfu/ml inoculum using a needle-less syringe (INFS), and infiltrating with 5 × 106 cfu/ml inoculum (INF6). No greenhouse method was superior in all assessment categories. The CARB method was most repeatable (t = 0.78) but had a low Spearman's correlation (rs = 0.29), indicating that greenhouse rankings did not correspond closely with field rankings. The INF6 method was unsuitable because it did not differentiate between plant genotypes. The DIP method appeared most suitable, having moderate repeatability (t = 0.46) for four observations per leaf and moderate Spearman's correlation with field performance (rs = 0.56). The INF5 method may be appropriate for identifying bacterial spot resistance that is associated with resistance in the leaf mesophyll.
Multidisciplinary integrated pest management (IPM) teams from seven states in the southeastern United States (Alabama, North Florida, Georgia, Kentucky, North Carolina, South Carolina, and Tennessee) met to develop standards for adopting IPM in fresh-market tomato (Lycopersicon esculentum L.) production. Teams were composed of growers, private consultants, extension personnel, and faculty. IPM practices available for use on tomatoes in the southeastern United States were identified and a survey to assess the current level of adoption of IPM practices was developed. The survey also allowed growers to identify insect, disease, and production problems; beneficial technology and research developments; and other information relevant to IPM adoption. In northern Florida, Georgia, Kentucky, North Carolina, and South Carolina, IPM adoption by tomato growers was classified as medium or high on >75% of the fresh-market tomato acreage surveyed. It appears these states may have met the federal mandate for IPM adoption. Tomato producers listed early blight, late blight, bacterial spot, bacterial speck, and bacterial wilt as the main disease problems; tomato fruit worm, thrips, and aphids as the primary insect problems; and poor weather conditions, government regulation, and labor as their primary production problems. Twenty-six percent of the producers throughout the region felt that the development of insect- and disease-resistant varieties would be most helpful to increase production.
The effect of four PGRs on production of `Barbara Karst' bougainvillea [Bougainvillea × buttiana (Bougainvillea glabra Choicy × Bougainvillea peruviana Humb. & Bonpl.) was determined. Liners were transplanted into 3.8-L containers with a soilless substrate on 6 Apr. 1995 and were pruned on 15 May (mean height and width 23.6 and 34.5 cm, respectively). Uniconazole (10 ppm), maleic hydrazide (2808 ppm), daminozide (5000 ppm), and paclobutrazol (50, 100, or 200 ppm) were applied as a foliar spray (to wet) by a compressed air backpack sprayer on 16 May (0 weeks after treatment [WAT]). Daminozide (5000 ppm) was reapplied 31 May and 13 June as described above. Soil drenches of 5, 10, or 20 ppm paclobutrazol were additional treatments. Two nonPGR-treated controls were included: pruned at 0 WAT, and pruned at 0 and 4 WAT. There were eight replications per treatment placed in a randomized complete block design on a container bed under full sun and drip irrigation. At 6, 9, and 12 WAT, growth, flowering, growth habit, number of structural branches (>15 cm long), and level of bacterial spot infection by Pseudomonas andropogonis were recorded. Marketability was recorded 12 WAT and phytotoxicity noted 1, 4, 5, 6, 9, and 12 WAT. No PGR treatment effectively suppressed growth, or enhanced quality or marketability of `Barbara Karst' bougainvillea grown in 3.8-L containers. Furthermore, daminozide reduced the number of structural branches and maleic hydrazide was phytotoxic.