Screening cotton cultivars for low-phosphorus tolerance: a comparison of hydroponic and field methods.

Background: Soil available phosphorus (AP) deficiency significantly limits cotton production, particularly in arid and saline-alkaline regions. Screening cotton cultivars for low phosphorus (P) tolerance is crucial for the sustainable development of cotton production. However, the effect of different growth media on the screening outcomes remains unclear. To address this, we evaluated the low P tolerance of 25 cotton cultivars through hydroponic culture at two P levels (0.01 and 0.5 mmol•L⁻¹ KH₂PO₄) in 2018 and field culture with two P rates (0 and 90 kg•hm⁻², in P₂O₅) in 2019. Results: In the hydroponic experiments, principal component analysis (PCA) showed that shoot dry weight (SDW) and P utilization efficiency in shoots (PUES) of cotton seedlings explained over 45% of the genetic variation in P nutrition. Cotton cultivars were subjected to comprehensive cluster analysis, utilizing agronomic traits (SDW and PUES) during the seedling stage (hydroponic) and yield and fiber quality traits during the mature stage (in field). These cultivars were grouped into four clusters: resistant, moderately resistant, moderately sensitive, and sensitive. In low P conditions (0.01 mmol•L⁻¹ KH₂PO₄ and 4.5 mg•kg⁻¹ AP), the low-P-resistant cluster showed significantly smaller reductions in SDW (54%), seed cotton yield (3%), lint yield (− 2%), fiber length (− 1%), and fiber strength (− 3%) compared with the low-P-sensitive cluster (75%, 13%, 17%, 7%, and 9%, respectively). The increase in PUES (299%) in the resistant cluster was also significantly higher than in the sensitive cluster (131%). Four of the eight low-P-tolerant cotton cultivars identified in the field and six in the hydroponic screening overlapped in both screenings. Two cultivars overlapped in both screening in the low-P-sensitive cluster. Conclusion: Based on the screenings from both field and hydroponic cultures, ZM-9131, CCRI-79, JM-958, and J-228 were identified as low-P-tolerant cotton cultivars, while JM-169, XM-33B, SCRC-28, and LNM-18 were identified as low-P-sensitive cotton cultivars. The relationship between field and hydroponic screening results for low-P-tolerant cotton cultivars was strong, although field validation is still required. The low P tolerance of these cultivars was closely associated with SDW and PUES. [ABSTRACT FROM AUTHOR]