Gamete selection was examined as a breeding tool in developing Phalaenopsis hybrids that are more extreme temperature tolerant. Four pairs of hybrid cultivars were cross-pollinated, and then exposed to two temperature extremes, 30 °C/25 °C and 14 °C/9 °C, during initial pollen tube growth. One of each pollinated orchid cultivar was placed in either of two growth chambers and exposed to an 11-hour photoperiod with an irradiance of 180 mmol·m-2·s-1 and a relative humidity of 70% for 3–7 days. The capsules were collected after 150 days. Protocorm development was evaluated after 73 days on a thermogradient table ranging from 10 to 30 °C. For cold-pollinated seeds, protocorm development was optimum at 22 and 28 °C (means of 290 and 250 protocorms per plate, respectively), whereas the greatest protocorm development for warm-pollinated seeds occurred at 20 °C (103 protocorms/plate). Protocorms were evaluated for leaf and root formation 125 days after initial plating. Transfer to warm or cold incubators occurred as seedlings matured. One year after the initial plating, seedlings were evaluated on the following criteria: weight, number of leaves, leaf width, leaf length, leaf area, number of roots, and root length. The pollination treatment significantly affected the number of roots per seedling, whereas table position during germination significantly affected weight. The weight, number of leaves, and average root length were significantly affected by the pollination treatment and incubator interaction. The interaction between pollination treatment and table position significantly affected weight, number of roots, and average root length. Additional replication is required to confirm the greater germinability of cold-pollinated seed at higher temperatures.
Leslie A. Blischak and Richard E. Veilleux
Kate A. Nishijima, Harvey T. Chan Jr., Suzanne S. Sanxter, and Edward S. Linse
A reduced heat shock period for `Sharwil' avocado (Persea americana Mill.) before quarantine cold treatment is described. The shortened heat pretreatment period of 8 to 12 hours, rather than the originally recommended 18 hours at 38C, is effective in reducing chilling injury symptoms when the pulp is at ≤2.2C during 16 days of storage. The reduced durations and the range of pretreatment hours affords packinghouses greater efficiency and more flexibility and will reduce handling costs relative to the longer exposure.
Aref A. Abdul-Baki, S. A. Haroon, and R. N. Huettel
Susceptibility of tomato (Lycopersicon esculentum Mill) genotpyes to the root-knot nematode Meloydogyne incognita and to heat stress can be evaluated in a single labor- and time-saving operation using a nondestructive in vitro excised root technique. Seeds are sterilized and germinated for 2 days on 1% water agar. Five-mm root sections are grown at 28 and 35 C for 30 days on Gamborg-B medium with and without nematode inoculum. Evaluation criteria include fresh and dry weight and the appearance of juveniles, adults, gulls, and egg masses. Evidence will be presented on the breakdown of resistance to M. incognita under high temperature stress.
Aneela Nijabat, Adam Bolton, Muhammad Mahmood-ur-Rehman, Adeel Ijaz Shah, Rameez Hussain, Naima Huma Naveed, Aamir Ali, and Philipp Simon
cellular integrity, measures of membrane stability before and after exposure to heat stress serve to provide quantitative data that have been found to be well-correlated with heat tolerance ( Wahid et al., 2007 ). The occurrence of wide variation in the
Konstantinos E. Vlachonasios, Dina K. Kadyrzhanova, and David R. Dilley
Heat-treatment of mature-green tomato fruit (Lycopersicon esculentum) for 48 h at 42°C has been shown to prevent chilling injury from developing after 2 or 3 weeks at 2°C. Using mRNA differential display, we recently cloned and characterized a cDNA that encodes a cytosolic class II small heat-shock protein (Le HSP17.6). The mRNA of Le HSP17.6 is up-regulated during heat shock and the level of transcription remains high during subsequent storage at chilling temperatures. We used mRNA differential display with gene-specific primers from the other small HSPs families and find that the transcription of the other small heat-shock proteins is up-regulated during heat shock and persists at elevated levels at 2°C for at least 2 weeks. When the fruits are returned to a permissive ripening temperature after the chilling period, the mRNA of the small HSPs declines slowly for 3 days. These results suggest that the persistence of the small heat-shock proteins at low temperatures may provide protection against chilling injury.
Hua Shen, Hongmei Du, Zhaolong Wang, and Bingru Huang
tolerance between warm-season and cool-season plant species ( DiPaola and Beard, 1992 ; Fry and Huang, 2004 ). Nutrient deficiency under heat stress has been observed in various cool-season turfgrass species, which may largely contribute to growth
Jinyu Wang, Patrick Burgess, Stacy A. Bonos, William A. Meyer, and Bingru Huang
turf stands that are characterized by narrow and fine leaf textures ( Christians and Engelke, 1994 ). They are well adapted to poor soil fertility, moderate shade, and acidic soil conditions; however, little is known regarding their tolerance to heat
Jingjin Yu, Hongmei Du, Ming Xu, and Bingru Huang
stress tolerance, including heat stress ( Kaplan et al., 2004 ; Mayer et al., 1990 ). Mayer et al. (1990) reported an increase in the abundance of γ-aminobutyric acid (GABA), β-alanine, alanine, and proline in cowpea ( Vigna unguiculata ) as a result
Jessica Chitwood, Ainong Shi, Michael Evans, Curt Rom, Edward E. Gbur Jr., Dennis Motes, Pengyin Chen, and David Hensley
not offer a clear illustration of accuracy in these heat tolerance claims ( Table 1 ; Fig. 1 ). ‘Donkey’, ‘Tyee’, and ‘Marabu’ were expected to maintain higher germination percentages at higher temperatures, but ‘Tyee’ had the lowest germination