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Grain Filling Patterns of Barley as Affected by High Temperature Stress

Md Rasel Rana
Department of Seed Science and Technology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md Masudul Karim
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md Juiceball Hassan
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md Alamgir Hossain
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Md Ashraful Haque
Department of Genetics and Plant Breeding, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Grain filling determines the grain weight, a major component of grain yield in cereals. Grain filling in barley depends on current assimilation and culm reserves (mainly water soluble carbohydrates). Nowadays barley is facing heat stress problem which is mostly responsible to reduce the yield of barley. A field experiment was conducted at the Field Lab, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during November 2015 to March 2016 to study the grain filling patterns and the contributions of culm reserves to grain yield under heat stress. The experiment consisted of two factors— barley cultivars and heat stress. The heat stress was imposed by late sowing. The tillers were sampled once a week during grain filling period to determine the changes in dry weights of different parts, viz., leaves, culm with sheath, spikes, and grains; and to examine the contribution of culm reserves to grain yield. The results in the experiment revealed that the grain yield was reduced by 22-28% due to the stress. The grain yield varied from 52 to 150 g m⁻² with the mean of 102 g m⁻² under control while it varied from 37 to 116 g m⁻² with the mean of 75 g m⁻² under heat stress. Among the cultivars studied BARI Barley-5, BARI Barley-2 and BARI Barley-1, seemed as high yielders while BARI Barley-3, BARI Barley-4, BARI Barley-6 as the low yielder under heat stress treatment. The reduction in grain yield was attributable mainly to lighter grain weight due to the stress. Heat stress drastically reduced the grain filling duration by 45–50%. However, the stress increased the grain filling rate by 6–53%. The amount of reserves remobilize to grain varied among the cultivars ranging from 4.8 to 12.77 mg spike⁻¹ in control and from 1.73 to 6.25 mg spike⁻¹ in stressed plants. The stressed barley plants exhibited lower accumulation of reserves in culm but they showed almost its complete remobilization to the grain. The contribution of culm reserves to grain yield varied from 1.13 to 19.52%, and 1.09 to 2.11% in control and in stressed plants, respectively. In conclusion, culm reserve is the important attributes in grain yield in Bangladeshi barley cultivars but the contribution remains almost unaffected due the post-anthesis heat stress.

Keywords: Grain filling, Water soluble carbohydrates, Culm reserves, Heat stress, Barley

Location: Field Laboratory of Department of Crop Botany, Bangladesh Agricultural University, Mymensingh

Start Date: 00-11-2015

End Date: 00-03-2016

Program Area: Variety and Species

Commodity: Barley

Objectives:

To determine the contribution of culm reserves to grain yield and to screen out the barley genotypes for heat tolerance and having the ability to accumulate more culm reserves with higher efficiency of its remobilization to grain.

Methodology:

Six cultivars of barley named BARI Barley1, BARI Barley2, BARI Barley3, BARI Barley4, BARI Barley5 and BARI Barley6 were the materials of this study which were collected from Plant Genetic Resource Centre, Bangladesh Agricultural Research Institute (BARI). The experiment was conducted in rabi seasons at the Field Laboratory of Department of Crop Botany, Bangladesh Agricultural University, Mymensingh between November 2015 to March 2016.The experiment was laid out as double factor experiment in Randomized Completely Block Design (RCBD) with 12 treatments and 3 replications. Factor A—six barley cultivars and Factor B—heat treatment (control and heat stress). Heat stress was imposed by late sowing at December 15, 2015. Seeds are sown at November 15, 2015 for control. The experiment consisted of 36 unit plots; each plot was 2 m × 1 m in size. Plot to plot distance was 0.5 m. There were five rows 0.2 m apart in a plot. Rows of the plots were oriented in east-west direction. Land was prepared and fertilizers were used in an ideal dose as per the suggestions of the BARI annual Yearbook. Intercultural operations were done as and when necessary as to ensure normal growth of the crops. The plots were irrigated after urea application (at 30 and 60 days after sowing, DAS). The plants in a 0.8 m2 (0.4m × 2.0 m) area were harvested at maturity for yield and yield components in all cases. The spikes were counted and the plants were dried for 48 h at 80°C and weighed to determine the biomass yield. All spikes were hand-threshed and weighed for grain yield. The WSCs in culms (with leaf sheaths) were extracted and measured using anthrone method (Yemm and Willis, 1954) as described in Hossain et al. (2009, 2010, 2011). The dried culm were chopped and milled to a rough powder. The culm powder were weighed and extracted once with 80% ethanol at 60°C for 30 min followed by 2 successive 15-min extractions with distilled water at 80°C. The extracts were combined and evaporated to dryness at 65°C. The dried carbohydrates were resolved in 5 mL distilled water. A fraction of the extract solution (about 1 mL) was taken in a Micro centrifuge tube (1.5 mL) and charcoal powder was added to it. After mixing the powder and extract solution with a vortex (touch mixer), the solution was centrifuged at 5000 (rpm) or 5 min to make a clear solution. The clear solution was diluted 5–10 times with distilled water. Diluted solution (0.1 mL) was mixed with ice-cold anthrone reagent (5 mL). The mixture was heated for 10 min in a boiling-water bath and subsequently cooled with ice water. The absorbance of the reacted solution for standard and samples was measured with a spectrophotometer at 620 nm. The content of WSCs in the sample was calculated as mg WSCs per gram of culm dry mass using regression equation. The amount of WSCs in culm at anthesis, milk ripe and maturity was estimated based on the dry mass of culm harvested at respective stages. The amount of remobilized culm WSCs was estimated from the difference between total culm WSCs at milk ripe/anthesis (maximum WSCs content) and residual culm WSCs at maturity as described (Ehdaie et al., 2006a).
Statistical analysis All data were analyzed statistically using statistical package program MSTAT-C and MS office Excel program

Source of Information: J Bangladesh Agril Univ 15(2): 174–181, 2017

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The cultivars exhibited variations in remobilization of culm WSCs to grains. The contribution, in general, was higher in high yielders compared to low yielders. It may be concluded that, the grain weight is most important factor causing large variations in grain yield among barley cultivars grown in Bangladesh. Both the current assimilation and remobilize culm reserves are attributable to the grain weight. High yielding cultivars especially BARI Barley-5, BARIBarley-2 and BARI Barley-1 have the higher potentiality to buffer grain yield under limited current assimilation as they can store higher amount of WSCs in culm.

Knowledge Management: Journal