Indices to screen for grain yield and grain-zinc mass concentrations in aerobic rice at different soil-Zn levels

Abstract

Zinc is an important micronutrient for both crop growth and human nutrition. In rice production, yields are often reduced and Zn mass concentrations in the grains are often low when Zn is in short supply to the crop. This may result in malnutrition of people dependent on a rice-based diet. Plant breeding to enhance low-Zn tolerance might result in higher yields and nutritional quality but requires effective selection criteria embedded in physiological insight into the Zn husbandry of the crop and applicable in field evaluation of advanced breeding material or in screening of existing varieties. Using existing and newly developed low-Zn tolerance indices, this study presents the results of screening experiments carried out in high-and low-Zn soils. Sixteen accessions of aerobic rice were grown under greenhouse conditions to conceptualize the indices and 14 under field conditions to validate the indices. As the differences in soil-Zn levels in these experiments did not result in differences in grain yield, literature data were used from experiments where the soil-Zn level did have an effect on grain yield, to further check the validity of the indices. Several indices were applied to evaluate the genotypic low-Zn tolerance performance in attaining (relatively) high grain yield, high grain-Zn mass concentration, or both. The results indicate that the grain-Zn mass concentration efficiency index is different from the grain yield efficiency index and that the low-Zn tolerance indices identified superior genotypes best. Amongst the indices tested, the low-Zn tolerance index for grain yield and the low-Zn tolerance index for grain-Zn mass concentration were closely correlated with grain yield and grain-Zn mass concentration, respectively. Therefore, the low-Zn tolerance index for grain yield was effective in screening for high stability and high potential of grain yield, and the low-Zn tolerance index for grain-Zn mass concentration was effective for grain-Zn mass concentration under low and high soil-Zn conditions.

Improving zinc bioavailability in transition from flooded to aerobic rice. A review

“…The tolerant wheat cultivar was not only more efficient in root Zn uptake, but also sevenfold more efficient than the sensitive cultivar in partitioning Zn to the grain (Holloway et al 2010). In contrast, Jiang et al (2008b) found no correlation between grain yield efficiency and grain Zn concentration in a comparison of data from two independent experiments with a total of 26 cultivars. The combination of high tolerance to Zn deficiency with high grain Zn seems a relevant breeding objective and may seem feasible given that some lines showed superior in both aspects.…”

Zinc allocation and re-allocation in rice

“…Using the same cultivation method in 20-L containers as reported above, plants of two accessions, Qinai-3-Hun and 90B290, both tested earlier for grain Zn levels under field conditions in China (Jiang et al, 2008b ), were grown in growth cabinets of the UNIFARM facilities of Wageningen University, Wageningen, the Netherlands. The basic plant nutrition, day length and temperature settings were as in Experiment 1, but in this experiment two seedlings were placed per foam.…”

“…Later studies on wheat showed that when post-flowering uptake was made possible also substantial proportions of grain Zn could be accounted for by post-flowering uptake (Garnett and Graham, 2005 ; Kutman et al, 2011 ). In nutrient solution experiments with rice ( Oryza sativa L.), post-flowering Zn uptake equaled or surpassed grain Zn content at maturity over a wide range of applied Zn levels (Jiang et al, 2008a ) and over a range of genotypes (Jiang et al, 2008b ). Also Mabesa et al ( 2013 ) observed that post-flowering uptake was larger than total grain zinc content over a range of tested rice genotypes.…”

Zinc and Iron Nutrition Status in the Philippines Population and Local Soils

“…ZnD in soils is effectively corrected by Zn fertilization (89). It can be applied to soil through surface application or soil incorporation (105, 109) through seed treatment (111–114), foliar application (115–119), and by dipping seedlings into Zn solution (120–122) or in combinations. Numerous available Zn sources have been tested and studied individually or in combinations (103).…”

“…The uptake of Zn in rice grains is suggested to be affected by the supply of Zn during the grain Zn loading period (139). The supply of Zn to the grains is via root uptake in Zn-sufficient conditions while grain Zn accumulation is via root uptake and remobilization in Zn-deficient conditions (111, 112, 140). Zn uptake and transport are the major bottlenecks for Zn biofortification in rice (141).…”