Long-term field performance of PHYA1 RNAi cotton cultivars reveals sustained yield advantage and improved fibre quality

Global demand for natural cotton fibre continues to increase, but the simultaneous improvement of fibre quality and yield remains a major challenge in cotton breeding. Here, we assess the 13-year field performance of PHYA1 RNA interference (RNAi)-derived cotton cultivars in Uzbekistan. In experimental-station trials, RNAi cultivars (‘Porloq-1–4’) showed a 14% yield advantage over four traditional cultivars (3.06 ± 0.45 versus 2.68 ± 0.37 t ha⁻¹, P < 0.001), together with longer fibre (1.22 ± 0.03 versus 1.14 ± 0.02 in, P < 0.001), lower micronaire (4.48 ± 0.26 versus 4.65 ± 0.21, P < 0.01) and higher fibre strength (31.7 ± 1.4 versus 30.8 ± 1.2 g tex⁻¹, P < 0.001). In regional production datasets spanning 13 administrative districts, RNAi cultivars also outperformed the traditional cultivar ‘Sulton’ in yield (3.16 ± 0.78 versus 2.95 ± 0.73 t ha⁻¹, P < 0.05) and maintained superior fibre quality. In an unweighted additive ANOVA of the regional five-genotype yield dataset, environment (zone × year) was the dominant source of variation (68.29%, P < 0.001), whereas genotype also contributed significantly (4.43%, P < 0.001). Multivariate analysis of combined HVI traits likewise identified significant genotype effects in both the experimental and regional panels, supporting consistent differences in fibre quality among genotypes. Stability analyses indicated that the RNAi cultivars were generally well adapted across environments, with ‘Porloq-2’ and ‘Porloq-4’ showing particularly consistent performance. Over 2013–2025, area-weighted RNAi yield increased from 2.81 to 4.22 t ha⁻¹, while fibre length increased from 1.21 to 1.25 in. Annual-mean correlation analyses showed no strong adverse yield–quality relationships in the RNAi group. Together, these results indicate that PHYA1 RNAi confers durable agronomic and fibre-quality advantages under long-term field conditions.