Latest Research on Wheat Seedling: Jan 2021

Winter Wheat Seedling Emergence from Deep Sowing Depths

Growers in low‐precipitation (<300 mm annual) dryland wheat‐fallow areas of the inland Pacific Northwest need winter wheat (Triticum aestivum L.) cultivars that emerge from deep sowing depths in dry soils. Stand establishment is the most important factor affecting winter wheat grain yield in this region. Despite poor resistance to disease, modest grain yield potential, and other problems, the outdated soft white winter wheat (SWWW) cultivar Moro is widely sown in these dry areas, due to its excellent emergence ability. All other SWWW cultivars are semidwarfs that carry emergence‐impeding Rht1 or Rht2 reduced‐height genes. From 12 sowing trials at 2 locations over 4 yr, we compared the emergence capability of Moro to (i) 8 SWWW cultivars and (ii) 16 SWWW advanced experimental Mororeplacement lines. Under both wet and dry soil conditions (soil water content in the seed zone ranged from 11 to 19 mm3 mm−3), seeds were sown deep, with 110 to 160 mm of soil cover. Moro always emerged fastest and achieved the best final stand compared with the semidwarf cultivars. The advanced experimental lines, which contained either no reduced‐height gene or a Rht1, Rht2, or Rht8 reduced‐height gene, had superior straw strength, disease resistance, and grain quality compared with Moro. The best‐emerging advanced experimental lines had coleoptile lengths >100 mm. Coleoptile length was associated with emergence capability among both cultivars (r2 = 0.71, P < 0.004) and advanced lines (r2 = 0.62, P < 0.001). From deep sowing depths in this study: (i) cultivars and advanced lines with Rht1 and Rht2 reduced‐height genes always emerged poorly compared with Moro; (ii) the Rht8 reduced‐height gene did not hamper emergence to the extent that Rht1 and Rht2 did; and (iii) several advanced experimental lines with long coleoptiles equaled or exceeded Moro for emergence. [1]


Relative Date of Wheat Seedling Emergence and Its Impact on Grain Yield

Emergence of wheat (Triticum aestivum L.) seedlings usually occurs over a period of several days, resulting in nonuniformity among neighboring plants. The impact of nonuniformity in time of emergence on grain yield has not been determined. We determined effect of planting depth on relative date of seedling emergence, and of relative date of emergence on grain‐bearing tillers and grain yield per plant. Large seed (39.8 ± 4.59 mg kernel−1) in 1989, and large (41.7 ± 3.83 mg kernel−1) and small seeds (24.3 ± 4.56 mg kernel−1) in 1990 were obtained from ‘Roblin’ wheat. Seeds were hand.planted at 25‐, 50‐, and 75‐mm depths on Neuborst clay loam (fine‐loamy, frigid, Aquic Haploborolls) at Portage la Prairie, MB. Plants were tagged the day they emerged, and individual plant yield was determined at harvest. Planting depths did not differ for total percent emergence in 1989, but in 1990, increasing planting depth led to decreased total emergence. Gompertz growth model predictions of inflection time, maximum emergence rate, and cumulative percent emergence indicated that seedling emergence rate decreased as planting depth increased, and the decrease was greater with small seed than with large seed. The first date on which seedlings emerged each year was designated as Day 1. Averaged across 2 yr, plants that emerged on Day 1 to 3 produced 1.4 times the yield of those emerged on Day 4 to 6, and 3.2 times the yield of those emerged on Day 7 to 9. Reduced yield of late emerged plants was due primarily to fewer grain‐bearing tillers. This research demonstrates the benefit of shallow placement of large seeds in minimizing variation in time of seedling emergence among plants, and increasing grain yield. [2]

Mapping QTLs for Phosphorus-Deficiency Tolerance at Wheat Seedling Stage

Soil phosphorus (P) deficiency is one of the major limiting factors to crop production throughout the world. It is an important strategy to breed varieties with improved P-deficiency tolerance for sustainable agriculture. The objective of this study was to map QTLs for P-deficiency tolerance in wheat, and develop molecular marker assisted selection in breeding wheat with improved P-deficiency tolerance. A doubled haploid (DH) population, consisting of 92 DH lines (DHLs) derived from P-deficiency tolerant wheat variety Lovrin 10 and P-deficiency sensitive variety Chinese Spring, was developed for mapping QTLs for P-deficiency tolerance. A genetic linkage map consisting of 34 linkage groups was constructed using 253 SSR markers. Shoot dry weight (SDW), tiller number (TN), shoot P uptake (SPU), and shoot P utilization efficiency (PUE) were investigated at seedling stage under P deficiency (−P) and sufficiency (+P) condition in two pot trials in 2002 and 2003, respectively. All traits segregated continuously in the population under either −P or +P condition. Significant positive correlations were found in between TN, SDW and SPU, whereas significant negative correlations were observed between PUE and SPU and between PUE and TN. Twenty and 19 QTLs were detected under −P and +P condition, respectively. The 39 QTLs were distributed on 21 chromosomal regions. There were three clusters of QTLs, which were associated with Xgwm25l (on chromosomes 4B), Xgwm271.2 (on chromosome 5A), and Xgwm121 (on chromosome 5D), respectively. Compared to the DHLs with all Chinese Spring alleles at the three loci, those with all Lovrin 10 alleles had, on average, much higher SPU, SDW and TN under −P condition in both trials, suggesting the importance of the three loci in controlling P-deficiency tolerance. It was interesting to find that two of the above three loci were closely linked with vernalization requirement genes VRN-A1 (on chromosome 5A) and VRN-D1 (on chromosome 5D). Potential implication of the linkage between P-deficiency tolerance and VRN genes was discussed. [3]

Effect of Exogenous Application of Brassinolide on Growth and Metabolic Activity of Wheat Seedlings under Normal and Salt Stress Conditions

The present study was carried out to show the effect of brassinolide on normal and salt stressed wheat plant. Grains of wheat (Triticum aestivum sakha 93) were divided into four groups: seeds supplemented with 20 ml distilled water (control); seeds treated with NaCl solutions (25, 50, 100, and 200 mM); seeds supplemented with 0.1, 0.5, 1 and 2 mgL-1brassinolide and seeds treated with a combination of 1mg.L-1brassinolide and the mentioned NaCl concentrations. Root and shoot lengths, fresh and dry weights were measured as indicators for growth and biomass assessments while carbohydrates, proteins, amylase and protease were estimated as indicator for metabolic activity. Treatment of wheat seeds with different concentrations of brassinolide particularly 1mgL-1 causes a significant increase in growth parameters, carbohydrate fractions, total soluble proteins in root and shoot and the hydrolytic enzymes amylase and protease. Gradual increase in NaCl concentrations from 25mM to 200mM sharply decreased growth compared with the control. Results of this investigation showed that 1mgL-1brassinolide counteracted the inhibitory effects of salinity. [4]

Seed and Seedling Performance of Bread Wheat (Triticum aestivum L.) as Influenced by Rate and In-Season Nitrogen Application

Field and laboratory experiments were conducted in the wheat growing belt of south-eastern Ethiopia to assess effects of rate and in-season N application on seed and seedling performance of local and improved bread wheat varieties. For the field experiments, a factorial combination of four N levels, two bread wheat varieties, and three times of N application were laid out in a Randomized Complete Block Design with three replicates. Laboratory tests were conducted in a Completely Randomized Design with four replicates to evaluate seed germination capacity and seedling vigor. The rate and timing of N application had significant (P = .01) effects on seed hectolitre weight, seed germination capacity and seedling vigor index. 1000-kernels weight was not affected by the rate of N application but significantly influenced by time of N application. Three times split application of N at 120 kg ha-1 resulted in significantly (P = .01) higher hectolitre weight, percentage of normal seedlings, seed germination speed, seedling dry weight and vigor index compared to the other treatments. The results revealed that application of 120 kg N ha-1 in three-split doses with ¼ dose at planting, ½ dose at mid-tillering and ¼ dose at anthesis led to enhanced seed quality and seedling performance of the crop. [5]

Reference

[1] Schillinger, W.F., Donaldson, E., Allan, R.E. and Jones, S.S., 1998. Winter wheat seedling emergence from deep sowing depths. Agronomy Journal, 90(5), pp.582-586.

[2] Gan, Y., Stobbe, E.H. and Moes, J., 1992. Relative date of wheat seedling emergence and its impact on grain yield. Crop Science, 32(5), pp.1275-1281.

[3] Su, J., Xiao, Y., Li, M., Liu, Q., Li, B., Tong, Y., Jia, J. and Li, Z., 2006. Mapping QTLs for phosphorus-deficiency tolerance at wheat seedling stage. Plant and Soil, 281(1), pp.25-36.

[4] El-Feky, S. S. and Abo-Hamad, S. A. (2014) “Effect of Exogenous Application of Brassinolide on Growth and Metabolic Activity of Wheat Seedlings under Normal and Salt Stress Conditions”, Annual Research & Review in Biology, 4(24), pp. 3687-3698. doi: 10.9734/ARRB/2014/11089.

[5] Deressa, H. and Nigussie-Dechassa, R. (2013) “Seed and Seedling Performance of Bread Wheat (Triticum aestivum L.) as Influenced by Rate and In-Season Nitrogen Application”, Journal of Experimental Agriculture International, 3(4), pp. 857-870. doi: 10.9734/AJEA/2013/3650.

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