Resolved concerns after 28 years of Bt cotton in China

Table 1 Yield and yield components of Bt cotton varieties bred at different time points

Variety	Boll density /(m^–²)	Boll weight /g	Lint percentage /%	Seedcotton yield /(kg·ha^–¹)	Lint yield /(kg·ha^–1)
DP33B^a	79.18b	4.51d	37.5c	3 571c	1 339d
SGK321	74.83b	4.82c	39.1b	3 607c	1 410c
SCRC21	89.49a	5.28b	40.8ab	4 725b	1 928b
SCRC28	89.69a	5.56ab	41.2a	4 987ab	2 055ab
K836	88.76a	5.82a	41.0a	5 166a	2 118a
Source of variance
Year (Y)	0.005 0	0.045 0	ns	0.035 0	0.021 5
Variety (V)	< 0.000 1	< 0.000 1	< 0.000 1	0.025 0	0.001 5
Y × V	ns	ns	ns	ns	ns

^aDP33B, developed by the USA Delta and Pine Land Company in 1993, incorporates the Bt gene for pest resistance. SGK321, SCRC21, SCRC28, and K836 are Bt cotton varieties bred in China in 2002, 2005, 2007, and 2012, respectively. The field trials were conducted in Linqing City, Shandong Province, with a planting density of 60 000 plants per hectare and following standard local agronomic practices

ISSN: 2523-3254