Genotypic variation of wheat (Triticum aestivum L.) in grain filling and contribution of culm reserves to yield

To study the genotypic variation in the rate of grain filling and contribution of culm reserves to yield in wheat, an experiment was conducted consisting 12 popular cultivars of Bangladesh, viz., BARI Gom21 (Shatabdi), BARI Gom22 (Shufi), BARI Gom23 (Bijoy), BARI Gom24 (Prodip), BARI Gom25, BARI Gom26, Akbar (BAW 43), BARI Gom18 (Protiva), BARI Gom19 (Sourav), BARI Gom20 (Gourab), Agrani (BAW38), and Kanchan (BAW28). Tillers were sampled from anthesis to maturity to determine the changes in dry weights of different parts to examine the contribution of culm reserves to grain yield. The results in the experiment revealed that the grain yield varied from 2.61 to 5.35 ton/ha with the mean of 4.18 ton/ha. Among the cultivars BARI Gom24, BARI Gom26, BARI Gom19, and BARI Gom23 appeared as high yielders while Kanchan, Agrani, BARI Gom20, BARI Gom22 as the low yielders. Generally, high yielding cultivars showed higher total dry mass accumulation compared to low yielding ones. Moreover, high yielding cultivars also showed higher water soluble carbohydrates (WSCs) contents in culm at milk ripe stage than the low yielders. In general, contribution of culm WSCs to grain yield was more in high yielders than low yielders and it ranged from 2 to 29% of total grain weight. So, higher contribution of culm reserves resulted in higher grain yield of wheat. Introduction Wheat is an important and most widely cultivated cereal crop in the world. It is the most important staple food of about two billion people (Shiferaw et al. 2013). Wheat is the second most important cultivated cereal crop after rice (2.92% of total area) in Bangladesh (BBS 2019a). The crop is cultivated all over Bangladesh during Rabi season with or without irrigation. It occupies about 4% of the total cropped area and 11% of the area cropped in Rabi season (NovemberFebruary), and it contributes 7% to the total output of food cereals (Anon. 2008). During 20172018 the wheat production was 10,99,373 m tons from 3,51,220 ha of land with an average grain yield of 3.18 tons per ha in Bangladesh (BBS 2019b). The grain yield in wheat (Triticum aestivum L.) can be described as the product of grain number per unit area and individual grain weight. The grain number can be determined during the period immediately before anthesis. The grain filling starts with the division of endosperm cells followed by the increase in number of cells through the accumulation of assimilate. The assimilate for grain filling comes from current assimilation and storage (reserve) pools in vegetative plant parts, especially in the culms (Karim et al. 2018). Water-soluble carbohydrates (WSCs) are considered as the main culm reserves, which may accumulate prior to anthesis and during the initial period of grain filling; and subsequently, they remobilize to developing grains (Bingham et al. 2009). Generally, the grain filling is supported only by current assimilation in the early grain filling, but by both current assimilation and culm reserves in the mid grain filling and only by culm reserves in the late grain filling (Takahashi et al. 1993). Due to that, grain filling in wheat *Author for correspondence: <alamgircbot@bau.edu. bd>. International Maize and Wheat Improvement Center (CIMMYT)-Bangladesh, Dhaka-1212. Department of Horticulture, Patuakhali Science and Technology University, Dumki, Patuakhali-8602