Journal of Integrative Agriculture 2014, 13(9): 1934-1942
September 2014
RESEARCH ARTICLE
Differences in the Efficiency of Potassium (K) Uptake and Use in Five Apple Rootstock Genotypes CHANG Cong, LI Chao, LI Cui-ying, KANG Xiao-yu, ZOU Yang-jun and MA Feng-wang State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling 712100, P.R.China
Abstract Plants that grow well while accumulating and transporting less potassium (K) perform better than more-sensitive plants when under deficiency conditions, which makes low-K-input and environmentally friendly agriculture possible. We conducted hydroponics and sand culture experiments to evaluate the efficiency of various apple (Malus domestica Borkh) rootstocks in their K uptake and utilization. Five genotypes were selected which are widely used in China - M. hupehensis Rehd, M. prunifolia Borkh, M. robusta Rehd, M. sieversii Roem, and M. rockii Rehd. Plant heights, root and shoot dry weights, and K concentrations were recorded. These genotypes differed markedly in dry weights, absolute and relative K concentrations, absolute and relative K accumulations, and their K efficiency ratio under deficient K conditions. The last parameter, expressed as relative shoot dry weight, was strongly and positively correlated with the other four parameters in each genotype. Therefore, we suggest that this parameter could serve as an index when selecting K-efficient genotypes. In this study, we have determined that M. sieversii and M. rockii are K-inefficient genotypes; M. prunifolia is K-efficient genotype; M. hupehensis and M. robusta have moderate levels of potassium efficiency. Key words: apple rootstock genotypes, potassium efficiency, genotype difference, potassium uptake, potassium utilization
INTRODUCTION Potassium (K) is one of the three major nutrients in soil-applied fertilizers. Described as the “quality element” (Usherwood 1985), it plays a vital role in plant growth and sustainable crop production (Jiang et al 2011). Globally, the consumption of K increased at an average rate of 4.4% per annum between 1999 and 2005, and it was predicted to rise by further 12%, to 35.2 million t K2O, by 2010 (Rengel and Damon 2008).
About one-quarter of the arable soils and three-quarters of the rice paddy soils in China are K-deficient (Yang et al. 2004). However, compared with nitrogen (N), application rates for K have remained relatively low and K fertilizer accounts for only 14% of total K inputs (Sheldrick et al. 2003). The N:K application ratio declined from 1.00:0.74 in the 1960s to 1.00:0.27 in the early 2000s (Krauss 2003). In China, K-fertilizer consumption relative to that of N is 50% lower than the average global ratio, indicating excessive use of N, or inadequate use of K, or both (Kirkby and Schubert 2013), thus leading to disrupt of soil-K balance. In the
Received 13 September, 2013 Accepted 10 February, 2014 CHANG Cong, E-mail:
[email protected]; Correspondence ZOU Yang-jun, Tel/Fax: +86-29-87082613, E-mail:
[email protected]
© 2014, CAAS. All rights reserved. Published by Elsevier Ltd. doi: 10.1016/S2095-3119(14)60839-X
Differences in the Efficiency of Potassium (K) Uptake and Use in Five Apple Rootstock Genotypes
late 1990s, China had a negative K balance (K application with potash fertilizers minus K removal by crops) of about 60 kg ha-1 yr-1, and that trend has continued downward (Syers et al. 2002). When K supply is inadequate, a decrease occurs in exchangeable or plant-available soil K, indicative of a loss of K from the soil-plant system (Xie and Zhou 2012). Nutrient deficiencies in plants are widespread throughout most agricultural regions in the world, especially in developing countries where fertilizers may not be affordable (Snapp et al. 2001). Cultivars with greater efficiency in their uptake and utilization of soil nutrients are likely to have positive environmental effects. This is because growers can reduce their usage of chemicals in agriculture and produce greater yields from soils where the effectiveness of fertilizers may be limited by chemical and biological reactions, topsoil drying, subsoil constraints, and/or disease interactions (Rengel and Damon 2008). Therefore, differences in the efficiency of nutrient utilization among genotypes is garnering more interest by scientists who focus on plant nutrition and breeding. Some plant genotypes vary in their efficiency of both uptake and utilization of K (Damon et al. 2007). Furthermore, their tolerance to K-deficiency stress can be quantified as the proportion of shoot dry weight under an adequate K supply versus weight under a deficiency, i.e., the K efficiency ratio (Rengel and Graham 1995; Yang et al. 2003; Damon et al. 2007). Considerable variation in efficiency of K uptake and utilization has been identified among existing genotypes of alfalfa (James et al. 1995), snap beans (Shea et al. 1968), soybean (Sale and Campbell 1987), tomato (Chen and Gabelman 1995; Figdore et al. 1989; Schwarz et al. 2012), ramie (Liu et al. 2000), maize (Farina et al. 1983; Arshad 2006; Cao et al. 2009; Samal et al. 2010), wheat (Woodend and Glass 1993; Wang et al. 2005; Damon and Rengel 2007; Samal et al. 2010), barley (Pettersson and Jensen 1983; Wu et al. 2011), rice (Yang et al. 2004), potato (Trehan and Sharma 2002; Trehan et al. 2005), sweet potato (George et al. 2002), canola (Damon et al. 2007), cotton (Zhang et al. 2007), and watermelon (Huang et al. 2013). Several researchers have reported that vigor of rootstock has a significant impact on the uptake of scion nutrient status in apples (Higgs and Jones 1991; Tagliavini et al. 1992; Aguirre et al. 2001; Fallahi et al. 2001; Webster 2004; Amiri 2014). The impact of precise nutrient application and the use of efficient rootstock
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on optimum fruit quality and yield in apples have been well documented during the recent years (Fallahi et al. 2002; Amiri and Fallahi 2009). Jones (1971) showed that xylem sap collected from various apple rootstocks was varied in their minerals composition suggesting that major genetic variation may exist in rootstocks with respect to their ability for uptake and translocation of minerals from the soil. Therefore, it is feasible to screen potassium efficient genotypes rootstock varieties to improve potassium use efficiency of apple trees. However, no one has reported on the K efficiency of apple rootstock cultivars. To ensure the reliability of the results, we designed two pilot experiments - hydroponics and sand culture - for screening our selected rootstocks. Our study objectives were to compare Chinese wild apple rootstock genotypes regarding their uptake and use of K, and to elucidate the principal mechanisms for any genotypic differences in efficiency.
RESULTS Plant heights Compared with the adequate-K (control) treatment, K-deficient plants of all tested apple genotypes were significantly shorter (P
