Search Results

You are looking at 31 - 38 of 38 items for

  • Author or Editor: Gregory A. Lang x
  • Refine by Access: All x
Clear All Modify Search
Free access

Gloria B. McClure, N. Suzanne Lana, and Gregory A. Lang

Commercially-produced, endodormant `Gloria' azaleas were placed into temperature × duration dormancy-breaking treatments at 2 month intervals to characterize seasonal variation in floricultural performance. Given the standard industry practice to break bud dormancy is 6 weeks at 3.5 to 7.2 C, three temperatures (3.5, 7.5, 11.5 C) and four durations (2, 4, 6, 8 weeks), plus a non-chilled control, were used to examine the contribution of each dormancy-breaking factor to subsequent floricultural quality. Treatment-Induced leaf abscission and flowering were quantitated, including days to Initial flowering and 50% flowering. Flowering response of dormant-budded azaleas produced during late spring and early summer (chilled during summer and early fall, respectively) was primarily and positively related to chilling duration, with only a minor influence of chilling temperature. In contrast, flowering of fall-produced endodormant plants (chilled during late fall) was best at 3.5 C, regardless of duration. Across all intervals, control plants averaged a leaf loss rate of 3 to 4 per day, suggesting a steady-state turnover rate. While leaf abscission was higher in all chilling-treated plants, those produced during fall and given the standard (or longer) chilling treatment exhibited about twice the total abscission (averaging as much as 20 leaves per day) as plants produced at other times, resulting in a clear reduction in plant foliar quality.

Free access

James W. Olmstead, Gregory A. Lang, and Gary G. Grove

Most sweet cherry (Prunus avium L.) cultivars grown commercially in the Pacific Northwestern states of the United States are susceptible to powdery mildew, caused by the fungus Podosphaera clandestina (Wall.:Fr.) Lev. The disease is prevalent in the irrigated arid region east of the Cascade Mountains in Washington State. Little is known about genetic resistance to powdery mildew in sweet cherry, although a selection (PMR-1) was identified at Washington State Univ.'s Irrigated Agriculture Research and Extension Center that exhibits apparent foliar immunity to the disease. The objective of this research was to determine the inheritance of powdery mildew resistance from PMR-1. Reciprocal crosses were made between PMR-1 and three high-quality, widely-grown susceptible cultivars (`Bing', `Rainier', and `Van'). Resultant progenies were screened for reaction to powdery mildew colonization using a laboratory leaf disk assay. Assay results were verified by natural spread of powdery mildew among the progeny in a greenhouse and later by placing them among infected trees in a cherry orchard. Segregation within the progenies for powdery mildew reaction fit a 1 resistant: 1 susceptible segregation ratio (P ≤ 0.05), indicating that resistance to powdery mildew derived from PMR-1 was conferred by a single gene.

Free access

Kay P. Gersch, Carl E. Motsenbocker, and Gregory A. Lang

Cayenne pepper fruit adhere tightly to the calyx/receptacle, increasing the cost of hand harvest and restricting mechanical harvest. Eight (8) cayenne pepper genotypes were selected from field observations to characterize fruit detachment forces(FDFs) and examine potential relationships between FDF and other fruit parameters. A preliminary greenhouse experiment revealed two genotypes with consistently lower FDFs and two with consistently higher FDFs over several progressive harvest. A field experiment confirmed these characteristics. No correlation between any fruit parameter and FDF was found to be consistent over the genotypes studied.

Free access

Robyn McConchie, N. Suzanne Lang, Alan R. Lax, and Gregory A. Lang

Premature leaf blackening in Protea severely reduces vase life and market value. The current hypothesis suggests that leaf blackening is induced by a sequence of events related to metabolic reactions associated with senescence, beginning with total depletion of leaf carbohydrates. It is thought that this carbohydrate depletion may induce hydrolysis of intercellular membranes to supply respiratory substrate, and subsequently allow vacuole-sequestered phenols to be oxidized by polyphenol oxidase (PPO) and peroxidase (POD) (Whitehead and de Swardt, 1982). To more thoroughly examine this hypothesis, leaf carbohydrate depletion and the activities of PPO and POD in cut flower Protea susannae × P. compacta stems held under light and dark conditions were examined in relationship to postharvest leaf blackening. Leaf blackening proceeded rapidly on dark-held stems, approaching 100% by day 8, and was temporally coincident with a rapid decline in starch concentration. Blackening of leaves on light-held stems did not occur until after day 7, and a higher concentration of starch was maintained earlier in the postharvest period for stems held in light than those held in dark. A large concentration of the sugar alcohol, polygalatol, was maintained in dark- and light-held stems over the postharvest period, suggesting that it is not involved in growth or maintenance metabolism. Polyphenol oxidase activity in light- and dark-held stems was not related to appearance of blackening symptoms. Activity of PPO at pH 7.2 in light-held stems resulted in a 10-fold increase over the 8-day period. Activity in dark-held stems increased initially, but declined at the onset of leaf blackening. There was no significant difference in POD activity for dark- or light-held stems during the postharvest period. Total chlorophyll and protein concentrations did not decline over the 8-day period or differ between light- and dark-held stems. Total phenolics in the dark-held stems increased to concentrations ≈30% higher than light-held stems. Consequently, the lack of association between membrane collapse, leaf senescence, or activities of oxidative enzymes (PPO or POD) with leaf blackening does not support the hypothesis currently accepted by many Protea researchers. An alternative scenario may be that the rapid rate of leaf starch hydrolysis imposes an osmotic stress resulting in cleavage of glycosylated phenolic compounds to release glucose for carbohydrate metabolism and coincidentally increase the pool of free phenolics available for nonenzymatic oxidation. The physiology of such a carbohydrate-related cellular stress and its manifestation in cellular blackening remains to be elucidated.

Free access

Nnadozie C. Oraguzie, David Ophardt, Matthew D. Whiting, Gregory A. Lang, and Lynn E. Long

‘PC8007-2’, more commonly known under the trademarked name, Kiona™, is a sweet cherry (Prunus avium L.) released in 2007 by the Washington State University (WSU) Sweet Cherry Breeding Program for fresh market production. In Pacific Northwest production areas of North America, Kiona™ blooms mid–late season, generally 4 to 7 d after ‘Bing’ and the large red–purple fruit ripen 6 to 9 d before ‘Bing’. The fruit are very flavorful and taste tests reveal high consumer appeal for the cherry.

Origin

Kiona™ originated at Prosser, WA, from a cross between ‘Glacier’ and ‘Cashmere’ made in 1980 by Tom Toyama,

Free access

James W. Olmstead, Matthew D. Whiting, David Ophardt, Nnadozie C. Oraguzie, and Gregory A. Lang

‘PC7064-3’, trademarked as Selah®, is a new sweet cherry (Prunus avium L.) for fresh market production released from the Washington State University (WSU) Sweet Cherry Breeding Program. In the Pacific Northwest of the United States production areas, ‘PC7064-3’ is a late midseason cultivar, maturing 10 to 14 d after ‘Bing’, and is an alternative for the maturity period of the standard cultivar Lapins (Lane and Schmid, 1984). ‘PC7064-3’ is one of the largest-fruited selections tested in the WSU Sweet Cherry Breeding Program, routinely averaging 12 g per fruit. Although ‘PC7064-3’ is self-fertile, it is only moderately

Free access

James W. Olmstead, Matthew D. Whiting, David Ophardt, Nnadozie C. Oraguzie, and Gregory A. Lang

‘PC7146-8’, more commonly known under the trademarked name Benton®, is a new sweet cherry (Prunus avium L.) for fresh market production released from the Washington State University Sweet Cherry Breeding Program. In the Pacific Northwest of the United States production areas, ‘PC7146-8’ is a midseason alternative to the standard cultivar Bing. ‘PC7146-8’ is similar in size to ‘Bing’ but blooms 3 to 5 d later, matures 1 to 2 d earlier, is self-fertile, has a higher resistance to rain-induced cracking, and has consistently been highly ranked in local comparisons of fruit organoleptic qualities (Long, 2006).

Origin
Free access

Nnadozie C. Oraguzie, D. Ophardt, Matthew D. Whiting, Gregory A. Lang, and Lynn E. Long

‘PC 7903-2’, more commonly known under the trademarked name, Cowiche™, is a sweet cherry variety released in 2007 by the Washington State University Sweet Cherry Breeding Program for fresh market production. In Pacific Northwest production areas of North America, Cowiche™ blooms moderately late, generally 4 to 7 d after ‘Bing’ (midseason industry standard), whereas harvest timing is usually 3 to 7 d later than ‘Bing’. Cowiche™ is vigorous and has an open canopy with a more pendant growth habit and slightly higher precocity than ‘Bing’. Its productivity on Gisela® 5 rootstock is similar to Chelan™’s but higher than