Author
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Skinner, Robert |
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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/8/2005 Publication Date: 9/23/2005 Citation: Skinner, R.H. 2005. Cultivar and environmental effects on freezing tolerance of narrow-leaf plantain. Crop Science. 45:2330-2336. Interpretive Summary: Narrow-leaf plantain is often planted in New Zealand pastures because of its high nutritive value, good drought tolerance, and ability to grow during winter months. However, use of plantain in the northeastern USA has been limited because of its poor winter survival. It is possible that the characteristics which allow for good winter growth in mild climates such as New Zealand might also be responsible for plantains poor survival in harsher environments. This hypothesis was tested by evaluating the freezing tolerance of two commercial cultivars 'Lancelot' and 'Tonic' that were developed under New Zealand conditions, and comparing them with an experimental line, 'PG700', developed from germplasm collected throughout the eastern USA. Growth rates at near freezing temperatures were also measured and compared with freezing survival to determine if reducing winter growth could improve freezing tolerance. The experiment was conducted twice. When the cultivars were compared, reduced growth at low temperature was not found to reduce freezing injury. In fact, PG700 had the greatest shoot growth rate at low temperature and the greatest survival after freezing to -14 degrees C. Survival rates of all cultivars in the second experiment were much lower than in the first, while shoot growth rates were much higher in the second experiment. In this case, greater low-temperature growth was related to greater freezing injury. These results suggest that factors associated with environmentally-induced changes in winter survival are not necessarily related to genetically-induced changes in freezing tolerance. Technical Abstract: Improved cultivars of narrow leaf plantain (Plantago lanceolata L.) have received increasing attention as possible pasture species for the northeastern USA because of their productivity during drought and high nutritive value. However, the cultivars currently available do not appear to have sufficient freezing tolerance to survive northeastern USA winters. This experiment examined the effect of growth and root:shoot partitioning during cold-hardening on the freezing tolerance of cultivars 'Lancelot' and 'Tonic' plantain compared with 'PG700', an ecotype collected from the northeastern USA. I hypothesized that PG700 would exhibit reduced shoot structural growth and increased partitioning of nonstructural carbohydrates to roots during cold-hardening, resulting in increased freezing tolerance and survival. In growth chamber experiments, seedlings were cold hardened for 21 d then frozen at -14 degrees C for 3 hr. Survival was evaluated after a 21 d recovery period. The experiment was conducted twice. Survival was greatest for PG700 (58%), followed by Lancelot (33%) and Tonic (18%) (P < 0.01). When combined across cultivars, survival was 59% in Trial 1 compared with 11% in Trial 2 (P < 0.01). None of the measured parameters including root and shoot growth, sugar concentration and content, or nitrogen concentration and content were related to genetic differences in freezing tolerance. Reduced survival in Trial 2 was accompanied by high nitrogen uptake and vigorous shoot relative to root growth during the cold-hardening period. These results suggest that factors associated with environmentally-induced changes in winter survival are not necessarily related to genetically-induced changes in freezing tolerance. |
