Title: Screening of rice varieties for higher Zn efficiency in paddy field
Author: Shahram MahmoudSoltani
Rice (Oryza sativa L.) is the major staple food for nearly 50% of people in the world, with Asia and Africa as the main rice-producing and consuming regions (90%). Despite their higher contributions to world rice production, they are severely dependent on rice’s versatility and considerable caloric value (70%). Zinc (Zn) next to N and P is the most important nutrient that its deficiency is considered to be a serious and widespread nutritional disorder of the world’s rice paddy fields and causes 20-80% yield reduction. Furthermore, with respect to the vitality of the increasing rice yields, Zn bio-fortification or the increasing of the bio-available Zn content in edible parts of agricultural crops is another immediate goal to improve the nutritional quality of crops to control human malnutrition disorders. According to the soil data bank of the soil and water department of the rice research institute of Iran, the available Zn content of more than 600 paddy fields in Guilan province is less than the critical level (>2 mg kg-1) and most broadly 200 out of 600 are less than 0.06 mg kg-1. To overcome this widespread Zn deficiency constraint that negatively influences rice yield and most broadly human health of rice-based food, further research is needed to explore and integrate all practical solutions to increase crop yield and quality of rice grains through varietal screening projects. The two factors split-plot experiment was conducted in a completely randomized design with three replications in the farmer field in 2018-2019. The experimental factors are the basal application of zinc sulfate at two-level (0, and 20 kg.ha-1 Zn) and rice varieties at 27 levels (local, improved, and lines). All conventional management practices, such as transplanting, watering, split application of fertilizers, weeding, and pest control were run on time and if necessary based on the rice research institute of Iran bulletin. In accordance with different rice growth stages, some of the collected morphological and physiological data were the plant height, tiller number, fertile tiller number, number of panicles, number of grains per panicle, total grain yield, dry weight of stem and leave; Zn in shoots, roots, and grains. Results showed that almost all of the collected data except panicle length, harvest index, flag leaves data were significantly affected by the basal application of Zn, and varieties and their interactions (P≤0.01 or P≤0.05). At zero Zn plots, the lowest and highest value of Zn contents were belonged to 18430-2 and Kadoos rice cultivars, respectively. Also, at 20 kg ha-1 Zn applied plots, the highest increased percentage of Zn content was found in Daylamani, Ghodsi, and Rash cultivars, respectively. The results of mean comparison analysis revealed that 18432-2 and 18431-1 (newly released lines) had lower and higher Zn uptake among all cultivars. There is very little opportunity to find and introduce the suitable lines or cultivars of rice by using only Zn uptake, and further morphological characters must be entered in the calculation. Therefore, GGbiPlot software was used to analyze the whole collected data for screening purposes. The results indicated that Gohar, Kadoos and Khazar cultivars were the most suitable lines not only at zero Zn plots, but also at 20 kg ha-1 Zn applied plots and less broadly Saleh, Daylamani, Guilaneh, and SA1 to cultivate them on Zn deficiency paddy soils or to select higher Zn uptake cultivar(s) for rice grain quality purposes.
Keywords: Varietal screening, local cultivars, improved cultivars, newly released lines, Zn deficiency