Comparison of yield and nitrogen use efficiency-related traits of cotton cultivars released during the last sixty years

The cotton breeding process is closely related to the improvement of soil fertility, innovation of culturing technology, climate change, and so on. The selection of lint yield-related traits is connected to the selection of traits of nutrient uptake and use efficiency. To understand the impact of the cotton breeding process on the nutrient efficiency of cotton, 22 cotton varieties released from the 1950s to 2013 in Xinjiang were grown together in a field with a randomized block design. The biomass, lint yield, N content and N use efficiency of each cultivar were analyzed. The results showed that there were significant differences in N use efficiency and partial factor productivity among the analyzed varieties. The biomass of the seeding stage, befuddling stage, flower and boll stage, and boll opening stage were 2.87-11.67 g, 20.8-38.6 g, 42.3-88.3 g, and 58.2-120.4 g per plant, respectively. Coefficients of variation were 30.2%, 8.2%, 5.6%, and 5.6%, respectively. For the yield components, the coefficient of variation of the boll number per plant was the highest (29.0%), and lint percent the lowest (1.0%). The variation of N use efficiency was 1.12-4.47 kg·kg^-1, and the partial factor productivity of N (PFPN) was 2.87-11.67 kg·kg^-1, with the coefficients of variation of 35.3% and 27.6%, respectively. It showed that PFPN had a significant correlation with biomass and lint cotton yield. The cotton economic coefficient had not changed significantly during the past 60 years and remained in a range of 0.20-0.24 g·g^-1. The lint yield of cotton increased gradually from 853.6 kg·hm^-2 in the 1950s to 1 569.8 kg·hm^-2 in 2013. There were significant changes in PFPN and N use efficiency:these factors increased from 4.12 kg·kg^-1 to 5.78 kg·kg^-1, and from 2.32 kg·kg^-1 to 3.07 kg·kg^-1, respectively. Based on lint yield components, N use efficiency and PFPN, the cotton varieties were divided into three groups:a high N efficiency group, a medium N efficiency group, and a low N efficiency group. Cluster analysis showed that 'Xinluzao 50' and 'Xinluzao 57' were the high N efficient varieties. Compared with the low-efficiency cultivar, the high N-efficiency cultivar had a higher lint yield and biomass. It can be concluded that high-yield cultivar selection could improve N use efficiency and PFPN of cotton.