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This project examined rose (Rosa ×hybrida) performance by measuring flower size and flower numbers per inflorescence in spring, summer, and fall seasons (mean temperatures 21.7, 30.0, and 18.1 °C, respectively) in interrelated rose populations. Populations and progeny differed in flower size as expected. Heat stress in the summer season decreased flower diameter (18%), petal number (17% to 20%), and flower dry weight (32%). Analysis of variance (ANOVA) showed a significant population/progeny × heat stress interaction for flower diameter indicating that rose genotypes responded differentially to heat stress. Flower size traits had moderate low to moderate narrow-sense (0.38, 0.26–0.33, and 0.53 for flower diameter, petal number, and flower dry weight, respectively) and moderately high to high broad-sense (0.70, 0.85–0.91, and 0.88 for flower diameter, petal number, and flower dry weight, respectively) heritability. Genotype × environment (G × E) variance (population/progeny × heat stress) for flower diameter accounted for ≈35% of the total variance in the field experiment indicating that heat stress had moderate differential genotypic effects. However, the genetic variance was several fold greater than the G × E variance indicating selection for flower size would be effective in any season but for the selection of a stable flower size (heat tolerant) rose genotype, selection would be required in both the cool and warm seasons. Seasonal differences in flower productivity of new shoots did not appear related to heat stress but rather to the severity of pruning conducted in the different seasons. The number of flowers produced on the inflorescence had moderate narrow-sense (h 2 = 0.43) and high broad-sense (H 2 = 0.75) heritability with a moderate genotype × pruning effect that explained about 36% of the variance.
The responses of garden roses to irrigation water with elevated salts are unknown. Two experiments were conducted to evaluate the relative salt tolerance of 13 self-rooted rose cultivars by irrigating the plants with nutrient solutions at an electrical conductivity (EC) of 1.4 dS·m−1 (control) or nutrient saline solutions at EC of 3.1, 4.4, or 6.4 dS·m−1. In Expt. 1, ‘Belinda’s Dream’, ‘Caldwell Pink’, ‘Carefree Beauty’, ‘Folksinger’, ‘Quietness’, and ‘Winter Sunset’ plants were grown in a greenhouse from 13 Aug. to 21 Oct. (10 weeks). Shoot dry weight of all cultivars decreased as EC of irrigation water increased. ‘Winter Sunset’ was most sensitive among these cultivars to salt stress followed by ‘Carefree Beauty’ and ‘Folksinger’ with severe leaf injury at EC of 3.1 dS·m−1 or higher or death at EC of 6.4 dS·m−1. No visual damage was observed in ‘Belinda’s Dream’ or ‘Caldwell Pink’, regardless of the salinity level. In Expt. 2, ‘Basye’s Blueberry’, ‘Iceberg’, ‘Little Buckaroo’, ‘The Fairy’, ‘Marie Pavie’, ‘Rise N Shine’, and ‘Sea Foam’ plants were grown in the greenhouse from 29 Sept. to 16 Nov. (7 weeks) and irrigated with the same nutrient or nutrient saline solutions. Salinity treatment did not affect shoot dry weight of ‘Basye’s Blueberry’, ‘Little Buckaroo’, ‘Sea Foam’, and ‘Rise N Shine’. Shoot dry weight of ‘Iceberg’, ‘The Fairy’, and ‘Marie Pavie’ decreased as EC of irrigation water increased. No or little visual damage was observed in ‘Little Buckaroo’, ‘Sea Foam’, and ‘Rise N Shine’. Leaf tip burns were seen in ‘Iceberg’, ‘Marie Pavie’, ‘Basye’s Blueberry’, and ‘The Fairy’ at EC 6.4 of dS·m−1. Generally, these symptoms were less severe than those observed in Expt. 1, probably attributable partially to the shorter treatment period. Whereas shoot Na+ and Cl– varied greatly among the rose cultivars, the shoot concentrations of Ca2+, K+, and Mg2+ did not. Generally, salinity-tolerant cultivars had higher shoot Na+ and Cl– concentrations. In summary, in Expt. 1, ‘Belinda’s Dream’ was the most tolerant cultivar, whereas ‘Winter Sunset’ was the least tolerant followed by ‘Carefree Beauty’. In Expt. 2, ‘Iceberg’, ‘Marie Pavie’, and ‘The Fairy’ were less tolerant to salinity as compared with other cultivars, although the differences were small.
Several rose species (Rosa rugosa, R. wichuraiana, R. setigera, R. laevigata, R. banksiae, R. roxburghii, R. odorata and hybrids) were employed to establish the appropriate nutrient media for shoot multiplication and root initiation of cultured shoots and to describe a procedure for the successful transfer to soil of plants obtained in vitro. Cultured shoot tips and lateral buds from different genotypes proliferated multiple shoots on a basal medium (MS salt, vitamins, glycine, sucrose and agar) supplemented with 0mg/l to 6mg/l 6-benzylamino purine (BA) and 0mg/l to 0.5 mg/l naphthalene acetic acid (NAA). Most rose species cultured in a modified MS medium supplemented with 2mg/l BA showed good growth and shoot proliferation. The buds nearest the apex exhibited the slowest rate of bud development. Root development was enhanced and shoot development inhibited by lowering the concentration of MS salts to quarter- and half-strength. With difficult-to-root species, rooting was improved by supplementing the media with auxin or giving them 3-7days of dark treatment.
Abstract
A sand culture system was used to compare growth reduction in Prunus rootstocks due to high A1 concentration. Aluminum at 50 mg liter-1 nutrient solution resulted in A1 tissue levels of 288 to 408 mg.kg-1, shoot growth reduction of 41% to 77%, and root growth reduction of 9% to 86%. Based on relative growth reduction, Prunus tomentosa Thunb. was more sensitive to A1 toxicity than were Nemaguard, Nemared, ‘Lovell’ [P. persica (L.) Batsch], P. besseyi Bailey, P. cerasifera Ehrh., and P. insititia L. Nemaguard and P. tomentosa had higher shoot A1 concentration at 50 mg Al/liter than the other rootstocks tested.
A high priority in rose (Rosa spp.) breeding research is the transfer of disease resistance, especially to black spot (Diplocarpon rosae Lib.), from wild diploid Rosa species to modern rose cultivars. To this end, amphidiploids (2n = 4x = 28) were induced with colchicine from five interspecific diploid (2n = 2x = 14) hybrids involving the black spot resistant diploid species R. wichuraiana Crép, R. roxburghii Thratt., R. banksiae Ait., R. rugosa rubra Hort., and R. setigera Michaux. Two application procedures (agitation of excised nodes in colchicine solution or tissue culture of shoots on medium with colchicine), five colchicine concentrations (0.0, 1.25, 2.50, 3.76, and 5.01 mmol), and five durations (2, 3, 5, 8, and 10 d) were used. After colchicine treatment, the materials were cultured in vitro and the surviving explants were examined for the “gigas” characteristics typical of doubled diploids. Chromosome counts of morphologically suspect genotypes confirmed 15 amphidiploids among 1109 plants that survived colchicine treatment. Although the effect of colchicine treatment varied some among interspecific hybrids, 2.50 mmol for 48 h of node agitation or 1.25 mmol for at least 5 d of shoot culture were optimal.