Search Results

You are looking at 91 - 100 of 304 items for :

  • "heat tolerance" x
  • All content x
Clear All
Free access

Ariana P. Torres and Roberto G. Lopez

and South America ( Bailey and Bailey, 1976 ). Tecoma ‘Mayan Gold’ was selected as a potential new annual flowering crop for patio use as a result of its compact structure, drought and heat tolerance, long-blooming characteristics, and few disease

Free access

K.M. Rainey and P.D. Griffiths

Yield components of 24 common bean (Phaseolus vulgaris L.) genotypes were evaluated following exposure during reproductive development to four greenhouse day/night temperature treatments (24 °C/21 °C, 27 °C/24 °C, 30 °C/27 °C and 33 °C/30 °C). Genotypes included 12 snap beans, two wax beans, six dry beans, and four common bean accessions; 18 genotypes were previously described as heat-tolerant and three were heat-sensitive controls. The highest temperature treatment reduced seed number, pod number, mean seed weight and seeds/pod an average of 83%, 63%, 47%, and 73%, respectively. A heat susceptibility index (S) measuring yield stability under high temperatures indicated that `Brio', `Carson', `G122', `HB 1880', `HT 20', `HT 38', `Opus', and `Venture' were heat tolerant. Heat-tolerant genotypes displayed differential responses to high temperature, suggesting different genetic control of heat tolerance mechanisms. Genotypes with moderate heat tolerance, including `Barrier' and `Hystyle', showed stable yields in the 30 °C/27 °C treatment only, indicating this regime is optimal for screening common bean materials of unknown heat tolerance. `Haibushi', `Indeterminate Jamaica Red', and `Tío Canela-75' were previously described as heat tolerant but exhibited a heat-sensitive reaction in this study. Heat-sensitive genotypes `Haibushi' and `Labrador' maintained mean seed weight under high temperature. This data will help utilize nonallelic heat tolerance genes in development of bean varieties grown in high temperature environments.

Free access

David W. Davis and Karl J. Sauter

Attention has been given in recent literature to crop breeding for heat tolerance, but, as with certain other physiological traits, such as photosynthetic efficiency, practical gain has lagged. The question remains as to whether heat tolerance can be improved, and, if so, if it can most efficiently be improved by a holistic approach, as in breeding for yield following timely high temperature levels in the field environment, or whether the breeding for heat (and drought) tolerance components in the laboratory would be feasible. At issue is the identification and repeatability of key plant responses, such as cell membrane damage, heat shock protein formation, increased ethylene output and other responses, and the relevance, effectiveness and cost of screening for such traits. Results from our laboratory, and the work of others, will be reviewed.

Free access

David W. Davis and Karl J. Sauter

Attention has been given in recent literature to crop breeding for heat tolerance, but, as with certain other physiological traits, such as photosynthetic efficiency, practical gain has lagged. The question remains as to whether heat tolerance can be improved, and, if so, if it can most efficiently be improved by a holistic approach, as in breeding for yield following timely high temperature levels in the field environment, or whether the breeding for heat (and drought) tolerance components in the laboratory would be feasible. At issue is the identification and repeatability of key plant responses, such as cell membrane damage, heat shock protein formation, increased ethylene output and other responses, and the relevance, effectiveness and cost of screening for such traits. Results from our laboratory, and the work of others, will be reviewed.

Free access

Aref A. Abdul-Baki, Sanaa A. Haroon, and David J. Chitwood

The Mi gene, which is the only source of resistance to the root-knot nematodes M. incognita and M. javanica in tomatoes, is effective only at soil temperatures below 28C. This single dominant gene exists in a homozygous form in certain tomato cultivars, in a heterozygous form in others, and is lacking in others. It has also been introduced into heat-tolerant and heat-sensitive cultivars. The availability of such genotypes allows determining whether a) the homozygous form provides more resistance than the heterozygous form and b) heat tolerance protects the Mi gene at high-temperature stress. The results of in vitro tests using excised roots show that the resistance offered by the Mi gene in the homozygous or the heterozygous form to M. incognita and M. arenaria was the same. The presence of heat tolerance gene did not protect the Mi gene from losing its effectiveness above 28C.

Free access

Aref A. Abdul-Baki

Nine heat-tolerant tomato [Lycopersicon esculentum (Mill.)] breeding lines, four heat-tolerant cultivars, and four heat-sensitive cultivars were evaluated in the greenhouse under high temperature (39C day/28C night) and in the field. Criteria for heat tolerance included flowering, fruit set, yield, fruit quality, and seed production. Under high-temperature conditions, the group of heat-tolerant lines, the heat-tolerant cultivars, and the heat-sensitive cultivars produced, respectively, the following per plant: flowers, 186, 94, and 55; fruit set 70%, 52%, and 30%; yield, 410, 173, and 11 g; and normal mature fruit, 72%, 37%, and 7%. Yields of heat-tolerant lines under high temperature in the greenhouse ranged from 118% to 31% of their respective yields in the field. Yields of heat-tolerant cultivars were 62% of those in the field. In contrast, yields of heat-sensitive cultivars under high temperature were < 1% of their respective yields in the field. High temperature induced flower abscission, reduced fruit set and yield, and increased the incidence of abnormalities. Major fruit abnormalities with high temperatures included cracks, blossomed rot, watery tissue, and small, immature fruits. Production of viable seeds under the high-temperature regime was severely reduced or totally inhibited regardless of the heat-tolerance level exhibited by the line or cultivar. The failure of heat-sensitive and most heat-tolerant cultivars or lines to produce viable seeds under such a high temperature suggests that a lower level of heat stress than that applied in these experiments could allow the production of enough seeds to test the relationship between heat tolerance in a genotype and its ability to produce viable seeds under high temperature. The results indicate that certain lines have high tolerance to heat and, therefore, could provide valuable sources of plant material for physiological studies to establish the physiological and molecular bases of heat tolerance. Some of the heat-tolerant lines might also serve as excellent germplasm sources in breeding heat-tolerant tomato cultivars.

Free access

R.J. Griesbach

Kangaroo paw is a new cut flower crop native to Australia. There are several interspecific hybrids with improved flower colors, heat tolerance, and growth habit. These hybrids are sterile due to divergent evolution of the parent species. Colchicine was used to double the chromosome number of one important sterile hybrid. This hybrid is everblooming. dwarf. and heat tolerant. The resulting allodiploid was fertile, and progeny are now being evaluated.

Free access

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.

Free access

J.W. Scott, S.M. Olson, H.H. Bryan, J.A. Bartz, D.N. Maynard, and P.J. Stoffella

`Solar Fire' is a heat-tolerant hybrid tomato (Solanum lycopersicum L. formerly Lycopersicon esculentum Mill.) with resistance to all three races of Fusarium wilt incited by Fusarium oxysporum f. sp. lycopersici Sacc. Snyder & Hansen. It has superior fruit-setting ability in comparison with most existing cultivars under high temperatures (>32 °C day/>21 °C night), and the fruit crack less under the rainy field conditions often present in the early fall Florida production season. Fla. 7776 is the pollen parent in `Solar Fire', providing much of the heat tolerance in this hybrid. It has large fruit-providing breeders with a parent to produce heat-tolerant hybrids with two heat-tolerant parents.

Free access

Xiaozhong Liu and Bingru Huang

Understanding physiological factors that may confer heat tolerance would facilitate breeding for improvement of summer turf quality. The objective of this study was to investigate whether carbohydrate availability contributes to changes in turf quality and root mortality during heat stress in two creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw. (syn. A. palustris Huds.)] cultivars, `L-93' and `Penncross', that contrast in heat tolerance. Grasses were grown at 14-hour days and 11-hour nights of 22/16 °C (control) and 35/25 °C (heat stress) for 56 days in growth chambers. Turf quality decreased while root mortality increased under heat-stress conditions for both cultivars, but to a greater extent for `Penncross' than `L-93'. The concentrations of total nonstructural carbohydrate (TNC), fructans, starch, glucose, and sucrose in shoots (leaves and stems) and roots decreased at 35/25 °C. The reduction in carbohydrate concentrations of shoots was more pronounced than that of roots. Shoot glucose and sucrose concentrations were more sensitive to heat stress than other carbohydrates. `L-93' maintained significantly higher carbohydrate concentrations, especially glucose and sucrose, than `Penncross' at 35/25 °C. Results suggest that high carbohydrate availability, particularly glucose and sucrose, during heat stress was an important physiological trait associated with heat-stress tolerance in creeping bentgrass.