The expression of cold resistance genes in wheat cultivars

English: Cultivars produce proteins in their normal life cycle. Some of these proteins are produced in greater quantities in reaction to cold temperatures in certain cultivars. In this study, 27 wheat cutivars were tested for their protein composition. The proteins produced could be divided into 14 different groups with each group having a certain molecular weight range. These groups were the same for the proteins in the coleoptiles and roots of wheat cultivars. Cold susceptible and tolerant cultivars were compared with each other to evaluate their differences in response to cold. The following was found: In the coleoptiles, the tolerant cultivars gained bands across the 14 groups in reaction to cold temperatures. This was also found in the roots of tolerant cultivars. Two of the susceptible cultivars tested (Adam Tas and SST 66), lost more bands in their coleoptiles across the different groups than they gained. The other two susceptible cultivars tested (Palmiet and Snack) gained more bands than they had lost. All the susceptible cultivars (except Palmiet) gained more bands in their roots in response to cold hardening. Palmiet gained and lost the same number of bands. Most cultivars produced more proteins in response to cold. Although proteins are produced in response to cold, not all the cultivars were able to produce the necessary proteins to make them more tolerant to cold. It was clear that some proteins were produced more in all or most cultivars in reaction to cold, but the susceptible and tolerant cultiavrs produced different proteins. In the coleoptiles, the susceptible cultivars had no change or gained bands in group 3 and group 11 while the tolerant cultivars had no change or lost bands in these groups. The susceptible cultivars lost bands (or there were no change in the number of bands produced) in group 4, group 10, group 12 and group 14. The tolerant cultivars gained bands in these groups in response to cold. In the roots, the susceptible cultivars gained bands (or there were no change in the number of bands produced) in group 5, group 11 and group 14. The cold tolerant cultivars lost bands in these groups. Only in group 2, did the cold susceptible cultivars lose bands, while the tolerant cultivars gained bands. The tolerant cultivars thus gained bands in their coleoptiles, whiel they produced fewer proteins in their roots in response to cold temperatures. The susceptible cultivars, however, produced more proteins in their roots than in their coleoptiles in response to cold. Jacobs (1999) found that some cultivars are susceptible to cold in their coleoptiles, but they are tolerant in their roots. SST 66 is an example of a cultivars that is susceptible to cold in its coleoptiles, but it is tolerant to cold in its roots. If one looks at SST 66, it is seen that this cultivars does not produce proteins in reaction to cold temperatures, thus reacting like a susceptible cultivar in its coleoptiles and like a tolerant cultivar in its roots. The susceptible cultivars produced more dark bands in their roots. Thus, the intensity of proteins increased in the roots of susceptible cultivars. In tolerant cultivars however, the intensity of proteins increased in the coleoptiles. Tolerant cultivars produced three times more dark bands in their coleoptiles than susceptible cultivars. If one looks at the production of certain groups, it is found that more proteins were produced in the coleoptiles of susceptible cultivars in group 6, group 8, group 9, group 10 and group 13. Only group 13 was produced in greater amounts in susceptible cultivars and not in the tolerant cultivars. In the coleoptiles of the tolerant cultivars, group 5 and group 7 were produced in greater amounts. It is however, not present in high amounts in susceptible cultivars. In the roots of cultivars, group 3, group 4, group 5 and group 9 can be correlated with cold temperature as it is produced in greater amounts in both the susceptible and tolerant cultivars. A higher intensity of proteins in group 6, group 13 and group 14 are correlated with susceptibility to cold, as it was only detected in susceptible cultivars. Tolerant cultivars produced these proteins in normal or low amounts in response to cold temperatures. Thus, the proteins with molecular weights of 54,5 - 50 kDa (group 5) and 43.5 - 39 kDa (group 7) could be used to screen for tolerance to cold in the coleoptiles of wheat cultivars, while the proteins with molecular weight of 60 - 55.5 kDa (group 4), 43.5 - 39 kDa (group 7) and 27 - 22.5 kDa (group 10) could be used to screen for tolerance to cold in the roots of wheat cultivars. It is further recommended that breeders discard any lines that show an increase in the production of proteins in their roots in the range of 49 - 44.5 kDa (group 6), 10. 5 - 6 kDa (group 13) and 5 - 0 kDa (group 14).