Blend response of four Egyptian cotton population types for late planting stress tolerance

Abstract

Abstract Background This study was conducted to investigate the effect of heterogeneity and heterozygosity on lint yield and fiber quality of Egyptian cotton for late planting stress tolerance. Lint yield was recorded in two planting dates among four cotton population types which included homozygous lines grown in pure stands, hybrids grown in pure stands, homozygous lines in blended stands, and hybrids grown in blended stands. Comparisons were made using trait means, blend response, and heterotic response. Stress susceptibility index (SSI) was calculated over planting dates. Results In normal planting date, the results showed that means of lint yield for homozygous entries (population I and II) were greater than mean yields of heterozygous entries (population III and IV). In late planting date, the results showed that mean of lint yield for some homozygous entries was equal mean yields of heterozygous entries. Regarding the yield, there was no significant difference between inbreds and blend of hybrids. However, the heterozygous populations had a lower (SSI) and more tolerance for late planting than homozygous populations. In late planting date, the two parents G.90 × CB.58 and G.95 had lint yield equal to or greater than means of blends (heterozygous populations). Adding to the two blends of inbreds, [((G.91 × G.90) × G.80)] + [G.90 × CB.58] and [((G.83 × G.80) × G.89) × (G.83 × Deltabine 703)] + [G.90 × CB.58] had the highest lint yield included the best inbred (G.90 × CB.58) suggesting that blend performance was determined by inbred performance. Conclusions Cotton blends may not provide buffering against late planting date. Blend response or heterotic response increased with late planting. However, cotton yields can sometimes be increased through the blends. Blends were not better than inbreds, and blend response was not consistent among the blends. Using blends is not recommended to increase yields or tolerance for late planting, and homozygous population’s cultivars could result in increased yields relative to blends. Assuming an efficient method for producing homozygous population’s cultivars was available, homozygous populations should be a viable option for commercial production to decrease observed losses in late planting date conditions.

Keywords

• Cotton
• Stress susceptibility index
• Blend and heterotic response