فهرست مطالب a. hassanzadeh ghorttapeh

Environmental stresses such as cold and heat are adversely affecting all aspects of crop plants including yield. In this study, the contents of fourteen amino acids and expression levels of four transcription factor genes including MYB1-1, KRP2, ERF and WRKY40 were analyzed in TN-97-2 (cold sensitive) and TN-97-290 (cold tolerant) local flax varieties under cold and heat stresses conditions. Seeds of two local flax varieties were grown in growth chamber of Biotechnology Institute of Urmia University, Urmia, Iran, under control conditions for 30 days. Then, plants were subjected to three different thermal regimes including control (25± 1°C), cold (4 ± 1°C) and heat (37 ± 1 °C) for three consecutive days.  Cold stress significantly increased the Asp, His, Ala and Met amino acids contents in both varieties. TN-97-290 variety exhibited less decline in His, Val, Phe, Iso and Leu contents than TN- 97- 2 variety under heat stress. Cold stress increased expression of ERF and WRKY40 mRNAs while heat stress elevated transcript levels of KRP2 and MYB1-1 genes in TN-97-290 variety. In summary, Asp, Glu, His, Ala and Met amino acids could be exogenously applied to flax plants by either foliar spray or root supplement to tolerate cold stress conditions. In addition, application of Ser and Pro amino acids may aid conferring heat tolerance to cold sensitive flax plants. The positive response of ERF and WRKY40 genes (cold stress) and KRP2 and MYB1-1 (heat stress) in TN-97-290 variety suggests their over-expression assist protecting flax plants under cold and heat stresses.

Since the economic value of a cultivar depends on its different characteristics, thus procedure of selection for several traits to achieve maximum economic value has always been considered by plant breeders. Therefore, accurate knowledge of the behavior and genetic relationship of these traits will help breeders to improve plant genotypes. In this study, 31 retrotransposon-based primers (12 IRAP and 19 REMAP primers) were used to identify molecular markers associated with 21 agronomic, morphological, and physiological traits in 45 different flax (Linum usitatissimum L.) genotypes based on a mixed linear model (MLM). Analysis of population structure by Bayesian method revealed two possible subgroups (K=2) in the population studied. Using MLM, a total of 29 loci associated with the 21 traits studied were identified (p < /em><0.01). The maximum number of associated loci was identified for 100-seed weight and seed yield traits. The existence of common markers among some traits studied, such as the significant relationship between LTR1-UBC808-2 marker with plant height and 100-seed weight, and LTR1-UBC807-4 with main stem weight and the number of capsules per the main stem can be due to pleiotropic effects or linkage between genomic regions involved in these traits. However, findings of the present study can be further strengthened with the inclusion of more markers putatively associated with economically important traits.