Insects can increase their survival at subzero temperatures, prior to long or short term exposure, to non-lethal COLD temperatures by COLD acclimation (ACC) or RAPID COLD HARDINESS (RCH). In this research, the effect of RAPID or gradual decrease in temperature on COLD tolerance of adults of the greenbug, Schizaphis graminum (Rondani) was investigated. LT50 (lower lethal temperature for 50% mortality) of aphids acclimated at 10°C for one week showed no significant differences with control (aphids reared at 20°C). In addition to the COLD acclimation, adults of S. graminum showed RCH response too. When the rearing aphids at 20°C were transferred directly to a range of sub-zero temperatures for 2 h, LT80 (lower lethal temperature for 80% mortality) was -11.6 °C, but acclimation at 0°C for 5 h before transfer to -11.6 °C, induced maximum RCH, led to increase of survival to 73%. RCH was induced by cooling of the insects at 0°C for different rates. Maximum survival (66%) was achieved by cooling at 0.05°C/min. Accumulation of sugars and polyols is one of the major mechanisms underlying ACC and RCH. In this study, trehalose and glucose increased considerably through ACC and RCH treatments, suggesting the role of these compounds in increasing COLD tolerance of S. graminum.

RAPID COLD HARDINESS in response to sudden decline in air temperature plays an important role in the aphid survival. RAPID COLD HARDINESS is a phenomenon that increases insect’ s survival at sub-zero temperatures following a brief exposure to low temperatures above 0 ° C. In this regard, the cabbage aphid Brevicoryne brassicae (L. ) is able to increase its COLD HARDINESS gradually during COLD season and produce large population on host plants in Brassicaceae family. In this research, RAPID COLD HARDINESS of B. brassicae, and its effects on development time, longevity and fecundity were investigated. Direct transfer of aphids from 20 ° C to a series of sub-zero temperatures for 2 h, resulted in a LT80 (estimated temperature required to kill 80% of tested population) of-7. 3 ° C. Preconditioning of first instar nymphs for 3 h and adults for 2 h at 0 ° C resulted in the highest survival rates of 63% and 71%, respectively. Acclimation of aphids, by a cooling rate of 0. 05 ° C/min form 20 to 0 ° C, prior the exposure to LT80 (-7. 3 ° C) resulted in the highest survival. No detrimental effects of RAPID COLD HARDINESS were observed on development time, longevity and fecundity. Results of the present study showed that RAPID COLD HARDINESS is induced in B. brassicae and increases the aphid survival in response to unexpected changes of temperature.

One of the most important problems of strawberry cultivation in temperate regions is winter COLD injuries. Current study investigated impacts of foliar application of glycine betaine (GB) at 0, 0. 5, 1, 2 and 4 mM concentrations on the COLD HARDINESS of strawberry. The plants were divided into two groups: one group for evaluation of COLD HARDINESS at temperatures of-6,-9,-12,-15 and-18 ° C; and the other for study of some biochemical characteristics. Results showed that GB treatment increased soluble carbohydrate and proline concentrations in both leaf and crown tissues, total protein concentration in leaf, and relative water content in leaf as compared to those in control. Based on LT50 calculated from electrolyte leakage and tetrazolium staining test, the GB application increased COLD HARDINESS in strawberry plant based on its concentration. The highest COLD HARDINESS was found in the 2 mM GB concentration based on electrolyte leakage and tetrazolium staining tests at-13. 3 and-15. 3 ° C. Meanwhile, the lowest values of COLD HARDINESS were observed in the control treatments based on electrolyte leakage and tetrazolium staining tests at-10. 2 and-11. 0 ° C. Significant correlations were found between soluble carbohydrate and proline concentrations in leaf and crown, and total protein concentration with LT50 calculated from electrolyte leakage and tetrazolium staining test. We conclude that application of 2 mM GB has the capacity to increase the freezing tolerance of strawberry and could be used as a prophylactic tool to reduce winter COLD injury.

Winter sown lentil compared with spring sowing, will enhance yield, provide better rotational and soil conservation system and consequently increase lentil area and production in Iran. COLD susceptibility in winter sown lentil is one of the abiotic stresses which affect its production. Hence, in order to evaluate the COLD HARDINESS of 39 lentil genotypes, obtained from the lentil germplasm collection of College of Agriculture Karaj, (Iran) and ICARDA (Syria), a randomized block design experiment with three replications was performed over the years 2000 and 2001 in Karaj conditions (NL 35o). The level of COLD HARDINESS among the lentil genotypes were measured by examining the alive and dead seedlings after being exposed to natural winter and spring COLD weather and expressed in percentage. The absolute minimum temperatures during the two growing seasons were -10oC and -9.8°c, respectively. Phenological traits (such as days to 50% flowering, seed filling period, maturity), seed yield and 1000 seed weight were recorded in each year. Pooled analysis of variance for genotypes response to winter sowing were statistically significant among various traits. The histogram for COLD HARDINESS percentage showed that the tolerant lentil genotypes (91-95% winter HARDINESS) comprised only 4% frequency percentage and the tolerant genotypes (71-90% winter HARDINESS) was 28 percent. The coefficient of variation for winter HARDINESS among the genotypes were about 17.5%. This variation is due to environment since no genotypic heredity for COLD HARDINESS in lentils has yet been reported. The lentil seed yield had a relatively higher variation (about 28.6%) compared to other traits. Nevertheless, the seed yield had a significant and positive correlation (r=%20**) with COLD HARDINESS percentage, and the high yielding genotypes also showed very high or high COLD HARDINESS percentage. Between COLD HARDINESS percentage and duration from sowing to harvest, a quadratic relation (R2= %19) existed and very high and high tolerant genotypes had shorter duration to maturity. On the whole, the lentil genotypes in this study were grouped into four clusters based on COLD HARDINESS percentage, seed yield and maturity traits. The high tolerant accessions 2, 36, 7, 13 and 32 along with relatively high tolerant accessions 16, 12 and 26 had the lowest euclidean distance and all were grouped in one cluster.

The beet moth, Scrobipalpa ocellatella is recognized as a widespread agricultural pest. COLD HARDINESS strategy of the beet moth larvae was investigated through monitoring seasonal changes at supercooling points and lower lethal temperatures. Furthermore, the role of microhabitat in winter survival was studied. The mean SCPs of the last instar larvae was not significantly different from November 2010 to April 2011. Mean inoculative freezing point(-8.0±1.44oC) of the last instar larvae was significantly higher than mean SCP (-14.9± 0.93oC). The COLD HARDINESSof the pest shows seasonal fluctuation in response to reduction of air temperature. A 50% mortality (LT50) occurred at -11oC in November and -14oC in January and reduced to -18oC in February and finally increased to -14.5oC in April.Glycerol, sorbitol, trehalose, and myo-inositol were identified components in whole body extracts of S. ocellatella larvae. However, total cryoprotectants could not have significant effects on the COLD tolerance. Larvae of S. ocellatella could tolerate subzero temperatures near their SCPs. Our findings show that beet moth larvae utilize moderately chilltolerance strategy during winter.

The inheritance of COLD HARDINESS in six inbred lines of Brassica napus L., Orakel, PF704591, Maluka, Global, Lisandra and Shiralee was investigated based on the field and laboratory evaluations, using a diallel mating system. A randomized complete block design with three replications was used to evaluate the winter survival of genotypes in the field. In order to evaluate genotypes in the laboratory, a split plot design with two replications was conducted and the amount of tissue water loss, percent of tissue water content and soluble carbohydrates after acclimation of plants along with percent of ion leakage, amount of tissue water loss and survival rate at freezing temperatures of -4, -7, -10 and -13 °C were measured. There were no significant differences among genotypes regarding to survival rate. However, under laboratory condition significant differences were observed among genotypes for all characters, except percent of tissue water content in the COLD stress condition. Comparison of means indicated superiority of Orakel over other parents for most of characters under both the COLD stress and non-stress conditions and Maluka × Global was the best hybrid with respect to COLD resistance traits. This hybrid showed high parent heterosis for all the characters studied and was better than Orakel for soluble carbohydrates and survival rate. Diallel analysis showed that Maluka and Global were better general combiners with respect to all characters studied before and after COLD stress. These parents had suitable combination of genes with additive effect which could be used in breeding programs for COLD HARDINESS. Among hybrids the largest specific combining ability was observed for Maluka × Global with respect to most of the characters. Therefore, more genes with dominant effect involved in controlling COLD resistance of this hybrid. Narrow- sense heritability estimates for all characters under study were low, but except for survival rate after freezing, the broad - sense heritability estimates ranged from %43.86 to %70.47 which indicated the importance of dominance gene action in controlling the traits under consideration.