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Kerry M. Strope and Mark S. Strefeler

Four heat-tolerant (`Celebration Cherry Red', `Celebration Rose', `Lasting Impressions Shadow', and `Paradise Moorea') and three non-heat-tolerant (`Lasting Impressions Twilight', `Danziger Blues', and `Pure Beauty Prepona') cultivars were identified using a Weighted Base Selection Index. These cultivars were used as parents in a full diallel crossing block with reciprocals and selfs. Progeny from five parents (25 crosses) were evaluated for heat tolerance. Four floral (fl ower number, flower diameter, flower bud number, and floral dry weight) and five vegetative characteristics (visual rating, leaf size rating, vegetative dry weight, branch number, and node number) were evaluated with emphasis placed on continued flowering under long-term heat stress. In addition, progeny from all seven parents (49 crosses) were evaluated for inheritance of adaxial leaf color, abaxial leaf color, vein color, and flower color. Significant differences were found in each data category (P < 0.001) with the exception of node number, which was not significant. Flower number varied from 0 to 2, flower diameter varied from 0 to 41 mm, floral dry weight varied from 14 to 105 mg, bud number varied from 0 to 12, branch number varied from 5 to 15, and vegetative dry weight varied from 220 to 607 mg. General and specific combining abilities of the parents were evaluated as was heritability. It was found that the four heat-tolerant cultivars had higher general combining abilities. Heat tolerance has low heritability and is controlled by many genes.

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Kerry M. Strope and Mark S. Strefeler

Fifty-three commercial New Guinea Impatiens cultivars (Impatiens hawkeri Bull.) from six different breeding series were tested for level of heat tolerance. Five floral (flower number, flower length, flower width, floral dry weight, and flower bud number) and five vegetative characteristics (leaf dry weight, stem dry weight, total dry weight, number of nodes, and number of branches) were evaluated with emphasis placed on continued flowering under long term heat stress. Significant differences among cultivars were found in each data category (P ≤ .0001). Flower number varied from 0 to 6, flower length varied from 10 to 51 mm, flower width varied from 10 to 47 mm, floral dry weight varied from 0 to 0.5 g, and flower bud number varied from 0 to 14. Four heat tolerant (Celebration Cherry Red, Celebration Rose, Lasting Impressions Shadow, and Paradise Moorea) and three nonheattolerant (Lasting Impressions Twilight, Danziger Blues, and Pure Beauty Prepona) cultivars were identified using a Weighted Base Selection Index. These cultivars were used as parents in a full diallel crossing block with reciprocals and selfs. One hundred seedlings from each of 49 crosses were evaluated for heat tolerance. General and specific combining abilities of the parents were evaluated as was heritability. It was found that the four heat tolerant cultivars had higher general combining abilities. Heat tolerance has low heritability and is controlled by many genes. Superior genotypes were identified (selection intensity of 0.05) and retained for further evaluation and breeding efforts.

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Robert W. Quené, Mark S. Strefeler, and Kerry M. Strope

The study was designed to provide information on the inheritance of certain characters important to drought tolerance in New Guinea impatiens. Seven genotypes, three were drought tolerant and four drought susceptible, were crossed in a full diallel with selfs. Drought tolerance of parents was estimated using stomatal conductance. At least 55 seedlings per cross were grown in the greenhouse for 2 months and evaluated for drought tolerance. Leaf fresh weight (LFW) leaf area (LA), leaf length (LL), leaf width (LW), and leaf thickness (LT) were measured using 10 leaves from each plant (parents plus progeny). From these measurements, we calculated LFW/LA and LL/LW. Stomatal conductance was measured on parents plus progeny of three crosses (drought tolerant × drought tolerant, drought tolerant × drought susceptible and drought susceptible × drought susceptible). Heritabilities and nonadditive and additive genetic variance for each trait were determined. All characters were significantly different between families. LFW/LA and LT was positively correlated with drought tolerance. The heritabilities for these traits were high, indicating that these characters can be used for selecting for drought tolerance in New Guinea impatiens and that rapid progress can be and was made in improving drought tolerance in New Guinea impatiens.