Presentation on theme: "Acquisition of Seed Desiccation Tolerance and Vigor in Wheat (Triticum durum) during Maturation as Influenced by Drying Methods Acquisition of Seed Desiccation."— Presentation transcript:
Acquisition of Seed Desiccation Tolerance and Vigor in Wheat (Triticum durum) during Maturation as Influenced by Drying Methods Acquisition of Seed Desiccation Tolerance and Vigor in Wheat (Triticum durum) during Maturation as Influenced by Drying Methods Samarah, N.H. 1, Al- Mahasneh, M.M. 2, Ghosheh, H.Z. 1, Alqudah, A.M. 1, Turk, M. 1 1 Department of Crop Production, Jordan University of Science and Technology, P. O. Box 3030, 22110, Irbid, Jordan. 2 Department of Plant Production and Protection, Faculty of Agriculture, Jerash Private University, Jerash, Jordan. ( INTRODUCTION Maximum seed viability and vigor generally occur at maximum seed dry weight (physiological maturity) and decline thereafter, as deterioration processes begin. The stage at which maximum quality is achieved during seed development has not been agreed (Rasyad et al., 1990; Pieta Filho and Ellis, 1991). The effect of air-drying wheat seeds in their spikes during maturation on seed desiccation tolerance and vigor compared with seeds extracted from spikes prior to drying under ambient, slow and fast conditions has not been studied. MATERIALS AND METHODSMATERIALS AND METHODS Seeds of wheat variety "Hourani-Nawawi" were sown during the growing seasons of 2005/6 and 2006/7 at Maru Station for Agricultural Research, Irbid, Jordan at a rate of 120 kg ha -1 using a grain drill. During seed development and maturation, spikes were harvested at five developmental stages: 1) milk stage (ML); 2) soft-dough stage (SD); 3) hard-dough stage (HD); 4) yellow-spike stage (physiological maturity) (PM); 5) brown-spike stage (harvest maturity) (B). The harvested seeds were subjected to four drying treatments:1) Air–drying the attached seeds in their spikes in ambient conditions (24 o C ± 2) (Spike drying); 2) Air- drying seeds hand detached from their spikes in ambient conditions (Ambient drying); 3) Slow drying the detached seeds over a series of saturated salt solutions declining in their relative humidity [sodium chloride (75% RH) for 72 h, magnesium nitrate (49% RH) for 48 h and potassium acetate (23% RH) for 48 h] in a closed container at 20 o C (Slow drying); 4) Fast drying the detached seeds over a saturated salt solution of low relative humidity [potassium acetate (23%) for 168 h] in a closed container at 20ºC (Fast drying). Standard germination was conducted for the dried seeds as described by ISTA (1999). OBJECTIVES To examine the effects of different drying treatments on seed desiccation tolerance and vigor of durum wheat at several developmental stages. CONCLUSION Drying the seeds in their spikes preserved seed desiccation at the Milk stage and seed vigor at later developmental stages, suggesting that spike-drying of wheat seeds maintained more stable seed quality across maturity stages and years. The two AA tests (42 o C for 96 h and 45 o C for 48 h) discriminated the differences among the drying treatments better than the AA of 41 o C for 72 h, especially in 2006/7. The involvement of the lemma and palea in the development of seed vigor of wheat needs further research. To identify the best accelerated aging test that discriminates among the seeds based on vigor, the seeds from the four drying treatments were exposed to three accelerated aging tests: 1) 41ºC for 72 h; 2) 42ºC for 96 h; or 3) 45ºC for 48 h. The design was a split-plot in a randomized complete block design with four replications. REFERENCES ISTA. (1999). International Rules for Seed Testing. Seed Science and Technology, 27, 333. Pieta Filho, C. and Ellis, R.H. (1991). The development of seed quality in spring barely in four environments. I. germination and longevity. Seed Science Research, 163, Rasyad, A., Vansanferd, D. and TeKrony, D. (1990). Changes in seed viability and vigor during wheat seed maturation. Seed Science and Technology, 18, Table 1: Standard germination test results for wheat seeds harvested at five developmental stages and exposed to four drying treatments in two growing seasons (2005/6 and 2006/7). Figure 1: Seed germination after the accelerated aging at 41 o C for 72 h, 42 o C for 96 h, and 45 o C for 48 h tests for wheat seeds harvested at five developmental stages and exposed to four drying treatments in two growing seasons (2005/6 and 2006/7). Bars indicate the LSD (P0.05). RESULTS AND DISCUSSIONRESULTS AND DISCUSSION Immature seeds harvested at the milk stage had maximum germination (100%) when seeds were dried in their spikes, while detached seeds dried by ambient, fast, or slow treatments had low germination (<62%) (Table 1). Detached seeds dried by ambient, fast, or slow treatments reached maximum germination when seeds were harvested at the soft-dough stage. Maximum seed vigor was attained at the SD stage for the spike drying treatment in both years (Figure 1). For the other drying treatments, the maximum vigor was attained at the HD stage and beyond and was very low in 2006/7 (as estimated by AA-germination of 42 o C for 96 h and 45 o C for 48 h). Our data suggest that drying the seeds in their spikes preserved the vigor of the seeds harvested at the immature stages (ML and SD stages) and at the later developmental stages (HD to B stages) in 2006/7.