Inflorescences of `Earliglow' and `Honeoye' strawberry (Fragaria ×ananassa Duch.) plants were subjected to controlled freezing tests to determine the cold tolerance of styles, anthers, and receptacles of individual flowers at various stages of development. Flowers of both cultivars tended to deacclimate as the stages of development progressed. Styles and receptacles generally exhibited injury at higher temperatures than anthers. The greatest deacclimation of styles and receptacles of primary flowers occurred at earlier developmental stages of `Honeoye' than of `Earliglow'. However, at the sixth stage of development, the critical temperature for receptacle injury in primary and secondary fruit was -3C for both cultivars.
Woon Kye Ki and Michele R. Warmund
Twelve peach (Prunus persica) cultivars, six apricot (Prunus armeniaca) cultivars, two japanese plum (Prunus salicina) cultivars, three european plum (Prunus domestica) cultivars, four sweet cherry (Prunus avium) cultivars, and three tart cherry (Prunus cerasus) cultivars were monitored for winter damage at New Mexico State University's Sustainable Agriculture Science Center in Alcalde, NM (main site), and the Agricultural Science Center in Los Lunas, NM (minor site), in 2011. Uncharacteristically low temperatures on 1 Jan. and 3 Feb. were recorded as −7.2 and −11.3 °F, respectively, at Alcalde, and 4.8 and −13.9 °F, respectively, at Los Lunas. On 10 Jan. at Alcalde, live peach flower bud percentage varied by cultivar, ranging from 11% for Blazingstar to 25% for PF-1, and 85% to 87% for Encore and China Pearl. Apricot flower buds were hardier, with 70% survival for ‘Perfection’, 97% for ‘Sunglo’, and 99% for ‘Harglow’ on 10 Jan. By 10 Feb., almost all peach flower primordia were discolored, with no cultivar showing more than 1% survival. Based on this information, the 10% kill of flower buds for most peach cultivars occurred at temperatures equal to or slightly higher than −7.2 °F, and 90% kill occurred between −7.2 and −11.3 °F. On 10 Feb., 0% to 15% of apricot flower buds on spurs or shoots of the middle and lower canopy had survived. For vigorous shoots in the upper canopy, apricot flower buds on 1-year-old shoots had a higher blooming rate than those on spurs of 2-year-old or older wood. Flower buds of japanese plum were also severely damaged with less than 0.2% survival for ‘Santa Rosa’ and 4.8% for ‘Methley’, but european plum were relatively unaffected with over 98% flower bud survival for ‘Castleton’ and ‘NY6’, and 87% for ‘Stanley’ after −11.3 °F at Alcalde. Cherry—especially tart cherry—survived better than peach, apricot, and japanese plum after all winter freezes in 2011.
Marie-Anne Boivin, Marie-Pierre Lamy, André Gosselin and Blanche Dansereau
A green roof system was installed on an existing 35-year-old building. The purpose of the study was to evaluate the effect of three substrate depths on low-temperature injury of six herbaceous perennials: bugleweed (Ajuga reptans), sandwort (Arenaria verna `Aurea'), sea pink (Armeria maritima), whitlow grass (Draba aizoides), creeping baby's breath (Gypsophila repens), and stonecrop (Sedum xhybridum). Plants in 4-inch (9-cm) pots were transplanted into three substrate depths: 2, 4, and 6 inches (5, 10, and 15 cm) and evaluated over a 3-year period. The analysis of the results showed that the species have different winter hardiness, therefore some species were subject to more freezing injury than others. Stonecrop had significantly more damage at 2-inch than 4- or 6-inch depths during the two winters. Bugleweed and creeping baby's breath showed more damage at 2 inches in 1996-97, not in 1995-96. Substrate temperatures were measured from Oct. 1995 to May 1997. Low temperature injury was more pronounced at 2 inch than at 4 or 6 inch depths. Minimum daily temperature and temperature variations measured in fall and spring of these 2 years were also higher at 4- and 6-inch depths.
Jeffery K. Iles and Nancy H. Agnew
The capacity of plant materials to resume normal growth after exposure to low temperature is the ultimate criterion of cold hardiness. We therefore determined the low-temperature tolerance of five commercially important herbaceous perennial species. Container-grown blanket flower (Gaillardia ×grandiflora Van Houtte. `Goblin'), false dragonhead [Physoste- gia virginiana (L.) Benth. `Summer Snow'], perennial salvia (Salvia ×superba Stapf. `Stratford Blue'), painted daisy (Tanacetum coccineum Willd. `Robinson's Mix'), and creeping veronica (Veronica repens Loisel.) were subjected to 0, -2, 4, -6, -8, -10, -12, -14, -16, and -18C in a programmable freezer. The percentage of survival of most species was adequate when exposed to -10C. Producers of container-grown perennials are advised to provide winter protection measures that prohibit root medium temperatures from falling below -10C.
Susan Lurie, Reuven Ronen and Shimon Meier
Storing `Maor' green bell peppers (Capsicum annuum L.) for 3 weeks at 2C resulted in the development of chilling injury (CI) evidenced as surface pitting. Fruit held at 8C did not develop any CI symptoms, but, after 3 weeks of storage, the fruit began to change color from green to red. PAM fluorometry was used to measure changes in photosynthetic competency in whole green bell peppers. Three photosynthetic characteristics could be measured by this method: quantum yield (Fm/Fe), photochemical quenching (Qp), and nonphotochemical quenching (Qnp). Fm/Fo decreased 90% during the first week of storage at 2C and remained low thereafter, while Qnp decreased after 2 weeks at 2C, just before the peppers began to develop CL Qp was similar at both storage temperatures. Potassium leakage as a CI measurement also increased in excised pepper discs after 2 weeks at 2C. The results indicate that PAM fluorometry can measure CI nondestructively before tissue damage is visible in green peppers.
Michele Renee Warmund, Patrick Guinan and Gina Fernandez
later. Research on the supercooling of floral primordia within dormant blackberry buds has been published ( Warmund and George, 1990 ; Warmund et al., 1988 , 1992 ), but low-temperature injury on shoots and floral buds after growth has begun has not
MiAe Cho, Brandon M. Hurr, Jiwon Jeong, Chaill Lim and Donald J. Huber
exhibiting watersoaking was 31% for 1-MCP-treated versus 64% for the control. Although there is little evidence that suppression of ethylene action ameliorates the sensitivity or tolerance of chill-sensitive commodities to low-temperature injury, it seems
Jeffery K. Iles, Nancy Howard Agnew, Henry G. Taber and Nick E. Christians
A major limiting factor in producing container-grown herbaceous perennials is low-temperature injury to cold sensitive roots and crowns during above ground winter storage. Growers and retailers of these plants understand the need for protection systems, yet specific recommendations are unavailable. The ability of several structureless systems to moderate temperature and protect 16 species of container-grown herbaceous perennials from low-temperature injury was investigated. Two light-excluding treatments consisting of 30 cm of straw between 2 layers of 4 mil white copolymer, and 18 cm deep in-ground beds protected with 1 layer of 4 mil white copolymer and 30 cm of woodchips provided the greatest moderation of winter low and early spring high temperatures but resulted in severe etiolation among test plants, A bonded white copolymer-microform overwintering blanket with translucent properties provided comparable plant survival, and prevented etiolated growth allowing plants to grow rapidly after uncovering, despite dramatic temperature extremes observed beneath this cover.
Saichol Ketsa, Sugunya Chidtragool and Susan Lurie
Freshly harvested mango fruit (Mangifera indica L. cv. Nam Dok Mai), were heated at 38 °C for 3 days or heated and then stored at 4 °C for 3 weeks before ripening at 25 °C, then compared with nonheated fruit for quality changes. When not refrigerated, heated and nonheated fruit ripened within 7 days to a comparable quality, although titratable acidity remained higher in heated fruit. The peel of heated fruit was initially yellower in cold-stored fruits, and soluble solids content was initially greater, whereas firmness and titratable acidity were less than that of nonheated fruit during ripening at 25 °C. After cold storage and ripening, heated fruit had a lower incidence of disease and developed less chilling injury than nonheated fruit. Nonheated fruit stored at 4 °C also developed off-flavors whereas the heated fruit did not. Heat treatment did not inhibit ripening but did ameliorate low-temperature injury.
S. Khanizadeh, Y. Groleau, J. Cousineau, B. Thériault, J.R. DeEll, C. Beldica and H. Boddington
One of the major problems affecting apple trees in Eastern Canada is low temperature injury during the winter and spring. Although there have been many studies on the cold hardiness of apple trees, no survey has been done on winter injury in Québec orchards. A survey was conducted in 1995/1996 to identify factors responsible for apple tree mortality during the winter of 1993/1994 in Québec. Three-hundred-thirty (330) apple orchards were visited and information on more than 50 characteristics were evaluated via a questionnaire; including hardiness, end use, shelf-life, etc. A full report is available at http://www.pgris.com. A large diversity of cultivars and rootstocks was observed in the Québec orchards, and thus a database was created containing information for all cultivars evaluated and the collected agronomic characteristics. Some of the more important information, such as hardiness, end use, shelf-life, scab resistance, etc., along with 265 apple images, were put together as a poster. A copy of this poster is available from http://www.pgris.com.