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Heat Stress Differentially Regulates Wheat Genotypes in Respect of the Contribution of Culm Reserves to Grain Yield

Md Rezaul Karim
Department of Agronomy, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md Amirul Islam
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh, present address: 3International Maize and Wheat Improvement Center (CIMMYT) Bangladesh

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

Ahmed Khairul Hasan
Department of Agronomy, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Md Sabibul Haque
Department of Crop Botany, 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 wheat depends on current assimilation and culm reserves. A field experiment was conducted at the Field Lab, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during October 2013–May 2014 to study the grain filling patterns and the contributions of culm reserves to grain yield under heat stress. The experiment consisted of two factors—wheat cultivars (10 cultivars) and heat treatments (control and heat stress). Heat stress was imposed by late sowing (Dec 20); the seeds were sown in normal time (Nov 15) for control. The tillers were sampled once a week during the 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 result in this experiment revealed that the grain yield was reduced by 3–49% due to the stress. 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 25–40%. However, the stress increased the grain filling rate by 6–60%. The stress-induced early leaf senescence indicated as the decline in SPAD readings. The result indicates less contribution of current assimilation to grain yield under the stress. However, the duration of stay green of leaves varied with the cultivars. The number of reserves remobilized to grain varied among the cultivars ranging from 0.52 to 1.2 g spike⁻¹ in control and from 0.44 to 0.97 g spike⁻¹ in stressed plants. The stressed wheat 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 33 to 67%, and 36 to 61% in control and in stressed plants, respectively. In conclusion, culm reserves are the important attributes in grain yield in Bangladeshi wheat cultivars but the contribution remains almost unaffected due to the post-anthesis heat stress.

Keywords: Culm reserves, Grain filling duration, Heat stress, Remobilization, Wheat

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

Start Date: 00-10-2013

End Date: 00-05-2014

Program Area: Crop-Soil-Water Management

Commodity: Wheat

Objectives:

To (i) study the grain filling pattern of Bangladeshi wheat cultivars under heat stress during grain filling, and (ii) evaluate the wheat cultivars in respect of the contribution of culm reserves under the heat stress.

Methodology:

A field experiment was conducted at the Field Lab, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during October 2013–May 2014. Ten wheat cultivars (Akbar, BARI Gom18, BARI Gom19, BARI Gom20, BARI Gom21, BARI Gom22, BARI Gom23, BARI Gom24, BARI Gom25, and BARI Gom26) were grown under heat treatments in the field in a two-factorial randomized complete block design (RCBD) with three replications. The seeds of wheat genotypes were collected from Regional Wheat Research Centre, BARI, Gazipur; and were sown on Nov 15, and Dec 20, 2013 for control and heat stress treatment, respectively. The wheat crops were grown following the standard cultivation techniques (Mandal et al, 2011).
Ten plants (tillers) were sampled once a week during grain filling period. Grain filling period was defined as the duration from anthesis to physiological maturity. The date of anthesis was determined when the anthers extruded in 50% of the spikes in the field and the date of physiological maturity was the day when the grain attained its maximum weight. Leaf greenness was measured with a chlorophyll meter (SPAD-502; Konica Minolta Sensing Inc., Osaka, Japan) at each sampling date. The plants were separated into a culm with sheath, leaves, and spike; oven-dried and weighed. The grains were separated from spikes, counted and weighed to determine the individual grain weight and grain growth patterns. The culms with leaf sheaths were milled for the measurement of water-soluble carbohydrates (WSCs) using the anthrone method (Yemm and Willis, 1954) as described in Hossain et al., 2012. The contribution of culm reserves was calculated based on the remobilized reserves from culm dry matter (DM) at milk ripe and at maturity. The data on yield and its attributes of the cultivars were collected and analyzed with Microsoft excel.

Source of Information: J Bangladesh Agril Univ 18(4): 894–900, 2020

Article Link (Online Journal): https://doi.org/10.5455/JBAU.127741

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The grain yield, biomass yield, harvest index, and yield components of ten wheat cultivars as affected by heat stress during the grain filling period. The heat stress had a significant effect (P<0.01) on grain yield. The stress imposed the reduction in grain yield by 3–49%. The grain yield varied from 353 to 535 g m⁻² with the mean of 452.3 g m⁻² under control while it varied from 257 to 428 g m⁻² with the mean of 342.3 g m⁻² under heat stress. The order of the cultivars in respect of grain yield under control condition was as follows: BARI Gom24 (535 g m⁻²) > BARI Gom26 (509 g m⁻²) > BARI Gom19 (500 g m⁻²) > BARI Gom23 (493 g m⁻²) > BARI Gom18 (487 g m⁻²) > BARI Gom21 (448 g m⁻²) > Akbar (421 g m⁻²) > BARI Gom20 (391 g m⁻²) > BARI Gom22 (372 g m⁻²) > BARI Gom25 (353 g m⁻²). However, the order for grain yield under stress condition was as follows: BARI Gom23 (428 g m⁻²) > BARI Gom18 (378 g m⁻²) > BARI Gom20 (367 g m⁻²) > BARI Gom22 (364 g m⁻²) > Akbar (354 g m⁻²) >BARI Gom26 (343 g m⁻²) > BARI Gom25 (342 g m⁻²) > BARI Gom24 (318 g m⁻²) > BARI Gom21 (274g m⁻²) > BARI Gom19 (257 g m⁻²). Likewise, the biomass yield showed significant differences (P<0.05) among the cultivars and also between the stress treatments. It ranged from 755 to 1151 and from 717 to 917 g m⁻² under control and stress treatment, respectively. Also, the harvest index (HI) significantly (P<0.01) varied with the cultivars and also with the heat stress. It ranged from 39.6 to 52.8% and from 27.4 to 50.3 % under control and stress treatment respectively.

Knowledge Management: Report/Proceedings