Two studies were performed to evaluate techniques for screening verticillium wilt of Capsicum annuum L. The first study tested inoculation methods. The original method involved mixing the inoculum with planting medium in a cement mixer for 1 h. Seeds then were planted in the infested medium. In the new technique, inoculum is poured directly into the row, and seeds are placed directly on top of the inoculum. Inoculum levels of 2000 and 1000 mcrosclerotia/g of soil were tested in the new “in-row” method. The disease severity of the “in-row” plants was significantly less than the plants inoculated by the original method. A significant difference remained between resistant and susceptible lines. There was no difference between inoculum levels. The second study compared three commercial planting media to the standard soil used in previous screenings. Disease severity did not differ among media, and all media showed significant differences between resistant and susceptible C. annuum lines.
An inexpensive, rapid, and reliable seedling screening technique was developed to identify sources of resistance to foliar blight of Capsicum annuum L. caused by the fungal pathogen Phytophthora capsici Leon. Leaf surfaces of test plants were inoculated with 500 to 1000 zoospores prepared in distilled water. Seedlings were incubated for 5 days in an easy-to-construct dew chamber and observed for symptom development. `Criollo de Morelos 334' chile seedlings, a Mexican land race resistant to root rot caused by the same fungal pathogen, were highly resistant to foliar blight. All commercial cultivars tested in this study, however, were highly susceptible. No root rot symptoms were observed in any of the foliar-inoculated plants.
Since its introduction more than 50 years ago, monogenic dominant “Type A” resistance has successfully controlled cabbage yellows, caused by Fusarium oxysporum Schlect. f. sp. conglutinans (Wr.) Snyd. & Hans., race 1 (FOCI). Recently, a new pathotype capable of overcoming Type A resistance was found in California and designated race 5 (3). Investigations of the relationship among the races revealed that race 1 and race 5 were more closely related to each other than they were to the other races, justifying the reclassification of the F. oxysporum on crucifers (P.W.B., unpublished data). F. oxysporum f. sp. conglutinans race 5 is now designated race 2 (F0C2).
The resistance of `Carolina Cayenne' (Capsicum annuum L.) to root-knot nematode Meloidogyne incognita (Kofoid & White) Chitwood races 1, 2, 3, and 4 was measured. Egg counts from roots were used to determine the plant's resistance to M. incognita. Few eggs were observed on `Carolina Cayenne' roots, whereas all races of M. incognita produced numerous eggs on the susceptible `NuMex R Naky' roots. The results indicated `Carolina Cayenne' is a source of resistance to all known races of M. incognita.
Nine pepper cultivars (Capsicum annuum L.) representing five pepper types were studied to determine water-loss rates, flaccidity, color, and disease development when stored at 8,14, or 20C for 14 days. Water-loss rate was markedly higher at 14C than at 8C, and was somewhat lower at 20C than at 14C. There were significant differences in water-loss rates between pepper cultivar with `NuMex R Naky', `NuMex Conquistador', and `New Mexico 6-4' (New Mexican-type peppers) having the highest water-loss rates. Flaccidity followed a pattern similar to water loss at each storage temperature, suggesting a direct relationship. Color development was cultivar- and package-dependent, and ratings increased with temperature. Placing pepper fruit in perforated polyethylene packages reduced water-loss rates 20 times or more, so that water loss no longer limited postharvest storage. Packaging also eliminated flaccidity and reduced color development across cultivars at 14 and 20C. Packaged fruit, however, developed diseases that limited postharvest longevity.
Physical characteristics [initial water content, surface area, surface area: volume (SA: V) ratio, cuticle weight, epicuticular wax content, and surface morphology] were examined to determine relationships between physical properties and water-loss `rate in pepper fruits. `Keystone', `NuMex R Naky', and `Santa Fe Grande' peppers, differing in physical characteristics, were stored at 8, 14, or 20C. Water-loss rate increased linearly with storage time at each temperature and was different for each cultivar. Water-loss rate was positively correlated with initial water content at 14 and 20C, SA: V ratio at all temperatures, and cuticle thickness at 14 and 20C. Water-loss rate was negatively correlated with surface area and epicuticular wax content at all temperatures. Stomata were absent on the fruit surface, and epicuticular wax was amorphous for each cultivar.