Evaluation of Cold Hardiness in Seven Iranian Commercial Pomegranate (Punica granatum L.) Cultivars

Abstract

<jats:p>Freezing injury is one of the most important limiting factors in commercial pomegranate production. The objectives of this study were to compare cold hardiness of seven Iranian pomegranate cultivars at three stages: November, January, and March, and to investigate the relationship between freezing tolerance and soluble carbohydrate and proline changes of shoots during acclimation and deacclimation. LT<jats:sub>50</jats:sub> values, estimated by both electrolyte leakage measurement (EL LT<jats:sub>50</jats:sub>) and tetrazolium stain test (TST LT<jats:sub>50</jats:sub>), allowed us to discriminate between the cultivars in terms of freezing tolerance. Acclimation and deacclimation did not occur simultaneously in different cultivars, having a key role in cold tolerance of cultivars, especially in fall and late winter. Post Sefid Bafgh cultivar showed high cold tolerance early in fall, but it was susceptible to cold during winter. ‘Naderi’, ‘Yusef Khani’, ‘Malas Saveh’, and ‘Robab Neyriz’ had the highest midwinter cold hardiness; ‘Mahabadi’ showed an intermediate hardiness, whereas ‘Post Sefid Bafgh’ and ‘Shishe Kap’ were found to be cold-susceptible in this period. Freezing tolerance estimated by TST corresponded to those measured by the EL method in all cultivars, but in November and January, higher variation in freezing tolerance was observed among the cultivars through TST compared with EL measurement. However, LT<jats:sub>50</jats:sub> values, estimated by EL measurement, were lower than those estimated through TST in November and March. Soluble carbohydrate concentrations of stem samples increased during cold acclimation from November to January; then it decreased in March. Proline had a narrow range of variation among the cultivars in November, but an increase in the amount of proline was observed during the period of hardening. In general, stronger correlations were observed between LT<jats:sub>50</jats:sub> values and the amounts of soluble carbohydrates compared with proline, particularly from fall to midwinter.</jats:p>

Foliar application of potassium sulphate enhances the cold-hardiness of grapevine (Vitis viniferaL.)

“…Means were compared using Duncan's multiple range test at the 5% level of significance (P ≤ 0.05). Correlation coefficients between soluble carbohydrate, proline, and protein concentrations and both EL-LT 50 and T-LT 50 values, estimated by electrolyte leakage and the tetrazolium stain test, were calculated using Pearson's correlation coefficient (Ghasemi Soloklui et al, 2012).…”

“…It is suggested that the activity of carbohydrate-metabolising enzymes, and the accumulation of carbohydrates, could be induced by K + ions. Yuanyuan et al (2009) andGhasemi Soloklui et al (2012) found a linear relationship between carbohydrate concentration and cold-hardiness, implying that the osmotic effect of carbohydrates probably prevented freezing injury in plants.…”

“…Tolerance to freezing is associated with a cold-acclimatisation process involving the osmotic stabilisation of cells, modifications in photosynthesis, the production of anti-oxidants, changes in hormone metabolism, and changes in cell wall composition (Lucau-Danila et al, 2012). During this process, the accumulation of osmo-regulants such as carbohydrates, proline, and proteins (Ghasemi Soloklui et al, 2012) prevents intra-cellular ice formation, which results in increased cold-hardiness in grapevine (Bigras et al, 2001). Moreover, accumulations of hydrophilic polypeptides, anti-oxidants, and chaperone proteins cause changes in the lipid composition of the plasma membrane, shifting it towards elevated levels of unsaturated fatty acids (Bakht et al, 2006).…”

“…Although a number of such factors have already been studied, there is little information regarding the effects of mineral nutrient elements on coldhardiness in grapevine. Physiologically, fertilising vines with P, K, and Mg enhanced the sugar and organic acid concentrations in shoots and canes (Robinson, 1992), resulting in increased cold-hardiness (Ghasemi Soloklui et al, 2012). Khristov and Lazarov (1994) investigated the effects of pre-planting applications of K and P on cold-hardiness in grapevine ('Dimyat') and found a higher ratio of bud survival in fertilised vines.…”

Seasonal Metabolic Investigation in Pomegranate (Punica granatum L.) Highlights the Role of Amino Acids in Genotype- and Organ-Specific Adaptive Responses to Freezing Stress

“…Despite numerous studies on cold stress responses in woody plants, there is little information on pomegranate responses to frost stress. Ghasemi Soloklui et al (2012) studied stem frost hardiness among seven 5-year-old pomegranate genotypes during one annual cycle and reported some of the tolerant and sensitive genotypes. They concluded that the content of soluble carbohydrates, especially from fall to mid-winter, is the best indicator of hardiness but, to date, the frost hardiness of mature pomegranate trees has not been reported.…”