GENOTYPIC VARIATIONS IN POTASSIUM UPTAKE AND UTILIZATION IN COTTON

Abstract

Genotypic differences in potassium (K) uptake and utilization were compared for eight cotton cultivars in growth chamber and field experiments. Four of the cultivars (‘SGK3’, ‘SCRC18’, ‘SCRC21’ and ‘SCRC22’) typically produce lower dry mass and the other four (‘Nannong8’, ‘Xiangza2’, ‘Xinluzao12’ and ‘Xiangza3’) produce greater dry mass in K-deficient solution (0.02 mM). The mean dry weight of seedlings (five-leaf stage) of cultivars with greater biomass was 155% higher than that of cultivars with lower biomass yield under K deficiency. However, all the genotypes had similar dry matter yields in K-sufficient solution (2.5 mM). Thus, the four cultivars with superior biomass yield under low K medium may be described as K efficient cultivars while the inferior cultivars may be described as K inefficient. Although seeds of the studied cultivars originated from different research institutes or seed companies, there were little differences in seed K content among them, irrespective of their K efficiency. Consequently, there were no significant differences in K accumulation in seedlings (4 d after germination in a K-free sand medium) just before transferring to nutrient solutions. However, the K efficient genotypes, on average, accumulated twice as much K at 21 d after transferring to K-deficient solution (0.02 mM). A much larger root system as well as a slightly higher uptake rate (K uptake per unit of root dry weight) may have contributed to the higher net K uptake by the K efficient cultivars. In addition, the K efficiency ratio (dry mass produced per unit of K accumulated) and K utilization efficiency (dry mass produced per unit of K concentration) of the K efficient cultivars exceeded those of the K inefficient genotypes by 29% and 234%, respectively, under K deficiency. On average, the K efficient cultivars produced 59% more potential economic yield (dry weight of all reproductive organs) under field conditions even with available soil K at obviously deficient level (60 mg kg⁻¹). We noted especially that the four K inefficient cultivars studied were all transgenic insect-resistant cotton, suggesting that the introduction of foreign genes (Bt and CpTI) may affect the K use efficiency of cotton.

Keywords:

• cotton
• potassium efficiency
• uptake
• utilization
• genotypic variation

ACKNOWLEDGMENT

The research was supported by the NSFC (National Natural Science Foundation of China, 30100111, 30571118), and the Cultivation Fund of the Key Scientific and Technical Innovation Project (707008), Ministry of Education of China. We thank Shandong Cotton Research Center for kindly providing seeds of ‘SCRC18’, ‘SCRC21’ and ‘SCRC22’, Guoxin Service General Union of Rural Technology (Hejian County, Hebei Province) for kindly providing seeds of ‘SGK3’, Nanjing Agricultural University for kindly providing seeds of ‘Nannong8’, Hunan Cotton Research Institute for kindly providing seeds of ‘Xiangza2’ and ‘Xiangza3’, and Huaxi Cotton Seed Company Ltd (Manasi County, Xinjiang Autonomous Region) for kindly providing seeds of ‘Xinluzao12’.