Daniel E. Legard and C.K. Chandler
John R. Stommel
Genetic characterization of anthracnose resistance in tomato (Lycopersicon esculentum Mill.) caused by Colletotrichum coccodes (Wallr.) Hughes was accomplished using populations developed from crosses between the anthracnose susceptible cultivar US28 and three resistant breeding lines (115-4, 625-3, and 88B147) that varied in their degree of anthracnose resistance and relative stage of adaptation for commercial use. These lines were of common parental lineage with resistance derived from the small-fruited L. esculentum USDA PI 272636. Anthracnose lesion diameters and fruit weight were measured in puncture inoculated fruit of parental, F1, F2, and backcross generations within each cross. Correlation coefficients between fruit size and lesion diameter were low and generally nonsignificant. Estimates of broad and narrow sense heritabilities for resistance were moderate and declined as relative anthracnose susceptibility of the resistant parent increased coincident with increasing horticultural adaptation. A simple additive dominance model, m[d][h], was adequate to explain the genetic variance for anthracnose resistance in all crosses. Genetic variance for anthracnose resistance was primarily additive. The minimum number of effective factors or loci conditioning anthracnose resistance declined during attempts to transfer high levels of resistance from PI 272636 into adapted breeding lines.
Peter J. Hofman, Marcelle Jobin-Décor, and Janet Giles
The potential to use percentage of dry matter (DM) and/or oil of the flesh of `Hass' avocado as a maturity standard to determine the latest harvest for acceptable fruit quality, was investigated. `Hass' avocado fruit were harvested from early October to mid-January from a commercial orchard in subtropical Queensland. The percentage of DM and oil changed little during the harvest period, and the eating quality of the flesh remained high. However, the incidence of body rots (caused mainly by Colletotrichum sp.) and the flesh disorders grey pulp and vascular browning, increased with harvest. These results indicate that percentage of DM and oil are not reliable late-maturity standards because of the inconsistent change with later harvests, and that disease and internal disorders can be the main determinants of latest acceptable harvest, rather than eating quality.
T. Vilasachandran and Steven A. Sargent
Pericarp browning, weight loss, and the associated quality deterioration are the unsolved postharvest problems of lychee (Litchi chinensis Sonn.). Freshly harvested fruits (`Brewster') were stored ± plastic wrap (99% and 84% relative humidity, RH, respectively) and ± panicle at 5°C for 18 days to simulate commercial handling scenarios. There were no significant losses in pericarp color (L*, hue angle, chroma value), total soluble solids, and total sugars from initial values for wrapped fruits. Wrapped lychees were 100% marketable, compared to 17% for unwrapped fruits. The former retained higher weight, moisture content and total titratable acidity (TTA, pulp), and lower pulp pH. Colletotrichum sp., Cladosporium sp., and Alternaria sp. caused decay in 56% of unwrapped fruits, whereas wrapped fruits were free of decay. Fruits with panicles had significantly higher weight loss (3%) than clipped fruits for both wrapped and unwrapped fruits. Pulp TTA tended to decrease and pH to increase more in fruits with panicle. Postharvest quality of lychee fruits was significantly extended by removing the panicle and maintaining nearly saturated RH during handling and storage.
Eric Hanson and Annemiek Schilder
Twenty cranberry (Vaccinium macrocarpon) genotypes were evaluated for five seasons in an experimental upland planting in southwest Michigan. Beds were constructed on a silty clay loam soil by excavating to grade, and filled with 30 to 45 cm of sand. Four 2 × 2-m plots of each genotype were planted in 1996. Fruit were harvested with hand scoops from 2000 to 2005. Yield per plot, average berry weight, and percent berries exhibiting decay were determined. Sound fruit were also stored at 2 °C for 4 to 8 weeks and sorted to determine the percentage of fruit developing decay in storage. Fungi were isolated and identified by morphological characteristics. Genotypes producing the highest average yields were `Stevens', `Ben Lear', #35, `LeMunyon', and `Franklin'. Varieties with the highest average berry weight were `Pilgrim', `Stevens', `Baines', `Beckwith', `Searles', and #35. Genotypes with lower rot incidence at harvest were #35, `Early Black', and `Foxboro Howes', whereas `Howes' and #35 developed the least rot during storage. Fungi commonly isolated from decaying fruit were Colletotrichum sp., Coleophoma empetri, Phomopsis vaccinii, Phyllosticta vaccinii, Fusicoccum putrefaciens, Botrytis cinerea, Pestalotia sp., and Allantophomopsis sp. Prevalence of specific fungi differed among cranberry genotypes.
R. Garca-Estrad, J. Siller-Cepeda, M. Bez, M. Muy, and E. Araiza
On Sinaloa State, tomato growers test new varieties every year looking high yield, better quality and long shelf life. However, few studies are done to know the resistance to postharvest diseases. The objective was to identify postharvest pathogens that infect this new tomato varieties with characteristics rin, nor or normals (BR84, S211, S69, and S121). Fruits in two stages of maturity (pink and red) were harvested and stored under simulated marketing conditions (20°C and 80% RH). Pathogens found were aisled on PDA and identified under microscope. Different chemicals were tested to control pathogens [NaOCl; Ca(OCl)2; Supersana; iodine; Citrucidal; Captan; and water]. Six fungus species—Alternaria alternata, Fusarium oxysporium, Rhizopus stolonifer, Colletotrichum sp., Rhyzoctonia sp, and Phomopsis sp—were found on all varieties. BR84 fruit (rin type) harvested on pink stage were more resistant than red ones. S69 fruit (nor type) were more susceptible at the pink than at the red stage. S121 fruits (normal type) were equally susceptible at both stages of maturity. Least resistant variety to fungus infection at both stages of maturity was S211 (rin type). Citrucidal and Ca(OCl)2 gave the best control.
Kaitlin Barrios and John M. Ruter
Press, St. Louis, MO Jacobson, A.L. 1996 North American landscape trees. Ten Speed Press, Berkeley, CA Little, E. 2016 Colletotrichum sp./spp. on Liquidambar formosana . Sample 44808. University of Georgia Plant Disease Report Royal Horticultural
E. Barclay Poling
Colletotrichum sp. infections in the initial stock plants that are used at the beginning of the strawberry propagation cycle (in contrast to hot water therapy). Dale (2007) provides an extensive discussion of the protocols used to test for viruses, mycoplasmas
Todd C. Wehner and Rakesh Kumar
-Sunshine’ have good fresh market quality and good keeping ability with very dark green fruit averaging 8 inches in length. ‘NC-Sunshine’ is resistant to anthracnose ( Colletotrichum sp.), powdery mildew ( Sphaerotheca fuliginea ), and scab ( Cladosporium
( Colletotrichum sp.), the three principal airborne defoliating diseases, in cultivars of the OWGB in Cordoba and in progenies and preselections of our program have shown high variability among descendants from the same cross. For peacock spot, with resistant