Four methods for screening carrot (Daucus carota L.) germplasm for resistance to bacterial soft rot were compared. There were differences in resistance among strains, with most severe damage caused by Erwinia carotovora pv. carotovora SR 394 (L.R. Jones) Holland and Erwinia carotovora pv. atroseptica SR 159 (van Hall) Jennison. Inoculation of cross-sectional root slices with bacteria applied in suspension-soaked paper disks produced the most consistent response. The severity of disease damage was proportional to bacterial suspension concentration. With the development of a standard screening method, it may be possible for breeders to breed carrots with reduced susceptibility to soft rot.
Barbara Michalik, Philipp W. Simon and Warren H. Gabelman
John Warner, Ray Cerkauskas, Tiequan Zhang and Xiuming Hao
Nine chinese cabbage (Brassica campestris ssp. pekinensis group var. cephalata) cultivars were evaluated for petiole spotting (gomasho) and bacterial soft rot (caused by Erwinia carotovora ssp. carotovora) in 1999 and fifteen in 2000 and 2001. The cultivars were arranged in a randomized complete block design in a Granby sandy loam soil with six replications in 1999 and three replications in 2000 and 2001, at the Greenhouse and Processing Crops Research Centre, Harrow, Ontario, Canada. Plants were harvested in the fall of each year during two harvest periods, one for early-maturing cultivars, and one for late-maturing cultivars. At harvest, the percent bacterial soft rot, percent marketable heads, plant size, uniformity of harvest maturity, and the mean head weight were determined for each cultivar. The number and weight of spotted leaves was determined by rating (0 to 5 scale) each leaf. Petiole spotting was also rated following storage at 2 °C (36 °F) and 89% ± 5% relative humidiyt for 3 to 4 weeks in 1999 and 2000. `Yuki', `Manoko', and `Summer Top' had lowest losses from bacterial soft rot while `Akala', `Ohken 75', `Spring Flavor', and `Yuki' had low levels of petiole spotting. Cold storage increased the incidence of the spotting disorder for most cultivars.
Sergio J. Carballo, Sylvia M. Blankenship, Douglas C. Sanders, David F. Ritchie and Michael D. Boyette
Commercial packing lines in Sampson County, N.C., were surveyed during two growing seasons to study handling methods on susceptibility of bell pepper fruits (Capsicum annuum L.) to bacterial soft rot (Erwinia carotovora subsp. carotovora). Samples were taken from two field packers and one packing house in 1991 and from two field packers and four packing houses in 1992. One field packer and one packing house were common to both years. Fruits were either inoculated with bacteria or untreated and stored at 10 or 21C. Damaged fruits were counted and classified as crushed, cut, bruised, abraded, and other injuries. Fruit injury was less dependent on whether the operation was a packing house or a field packing line than on the overall handling practices of the individual grower. In general, packing peppers in packing houses resulted in an increased number of bruises, whereas fruit from field packing lines had more abrasions. More open skin injuries resulted in greater fruit decay. In both years, fruits stored at 10C had less top rot than fruits stored at 21C. In 1992, they also had less pod rot. Dry and chlorinated lines often had equivalent rot problems.
Sarah M. Smith, John W. Scott and Jerry A. Bartz
When tomato (Lycopersicon esculentum Mill.) fruit come in contact with water at the packing house dump tanks, they can infiltrate water through the stem scar. If the water is infested with Erwinia carotovora, the fruit can infiltrate the bacteria, which will later develop into bacterial soft rot. To determine the inheritance of low water infiltration and thus tolerance to soft rot, a complete diallel was produced using six parents that infiltrate different amounts of water. The parents and hybrids were grown in a completely randomized block design with three blocks and 10 plants per block. The amount of water infiltrated by the fruit was measured by the change in weight after the fruit were immersed in water in a pressure cooker for 2 min. Both general combining ability (GCA) and specific combining ability (SCA) were significant, with GCA having a higher significance than SCA. There appeared to be a cytoplasmic effect on water uptake, where less water was taken up when the low-uptake parent was used as a female. When orthogonal contrasts were performed on reciprocal hybrids from parents that were significantly different, 33% of them were significantly different.
S.M. Smith, J.W. Scott, J.A. Bartz and S.A. Sargent
Bacterial soft rot, commonly incited by Erwinia carotovora (Jones), causes significant losses each year in many types of fresh produce, most frequently under warm, moist conditions. The disease is often found in fresh market tomatoes ( Solanum
S.M. Smith, J.W. Scott, J.A. Bartz and S.A. Sargent
Bacterial soft rot causes significant losses to many fresh vegetables, including fresh market tomatoes. This disease is sometimes seen in the field and is not uncommon when a crop has endured persistently wet conditions. The disease can develop
Jianping Ren, Michael H. Dickson and Elizabeth D. Earle
Swee-Suak Ko, Woo-Nang Chang, Jaw-Fen Wang, Shin-Jiun Cherng and S. Shanmugasundaram
In the tropics, onion (Allium cepa L.) bulbs are usually stored in shelters under ambient conditions resulting in severe storage losses. This study was aimed at determining whether variation in bulb storability exists among short-day onion cultivars and whether the trait can be improved through conventional breeding. Twelve onion cultivars with different degrees of storability were selected from preliminary experiments. Bulbs of selected cultivars were grown and stored for 3 months under ambient conditions. Observations were made on disease incidence at harvest, percentage diseased bulbs, and storage disease incidence of bacterial soft rot [BR (Pseudomonas gladioli pv. alliicola Burkholder)], black mold [BM (Aspergillus niger Tiegh.)], and fusarium basal rot (Fusarium oxysporum Schlechtend.:Fr. f. sp. cepae) after 3 months of storage. Data on bulb characteristics such as bulb fresh weight (FW), dry matter (DM) content, total soluble solids (TSS), and pyruvic acid content were recorded at harvest. Mean storage losses of cultivars ranged from 21% to 99% over 3 years. Diseases were the major causes of storage losses, with BR and BM being the most predominant. Performance of most traits (including storage losses) was significantly influenced by year (Y), cultivar (G), and Y × G interaction. Heavy rainfall during bulb development in 1997 may have contributed to higher disease incidence at harvest, higher percentage of diseased bulbs during storage, and lower DM, and TSS of the cultivars. Cultivars with good storability, such as `Red Pinoy' and `Serrana', were less sensitive to stressful environments and high disease pressure. Incidence of storage diseases was significantly correlated with DM (r = -0.65 to -0.84) and TSS (r = -0.66 to -0.87), as well as incidence of BR (r = 0.57 to 0.94) in each year. Thus, they could be good indicators for evaluating storability. Cultivars with good storability tended to have small bulbs, as average bulb FW was positively correlated with incidence of storage diseases. Disease incidences on `Red Pinoy' and `Serrana', both in the field and in storage, were significantly lower than in the other cultivars, indicating they are tolerant to major storage diseases and that they could be used as donor parents for genetic improvement of onion storability.
Juan Carlos Díaz-Pérez
keeping period at 20 °C, fruit were evaluated for presence of bacterial soft rot (caused by Erwinia spp.), which was reported as percentage of incidence (percentage of infected fruit with respect to total fruit number). Statistical analysis. Data were