Effects of combining Renlon with Renbarb1 and Renbarb2 on resistance of cotton (Gossypium hirsutum L.) to reniform nematode (Rotylenchulus reniformis Linford and Oliveria)

The upland cotton ( Gossypium hirsutum L.) germplasm lines BARBREN-713, having the Ren barb1 and Ren barb2 quantitative trait loci (QTL), and LONREN, carrying the Ren lon QTL, have introgressed resistance to reniform nematode ( Rotylenchulus reniformis Linford and Oliveria). Stunting has been observed in the LONREN source of resistance when subjected to heavy nematode pressure but not for BARBREN-713. To investigate the potential to reduce stunting in the LONREN source of resistance, cotton lines were developed with different combinations of reniform nematode resistance QTL from LONREN and BARBREN-713. Marker assisted selection was conducted to identify the following QTL combinations: (1) Ren barb1 + Ren barb2 , (2) Ren barb1 + Ren barb2 + Ren lon , (3) Ren barb2 + Ren lon , (4) Ren barb1 + Ren lon , (5) Ren barb1 alone, (6) Ren barb2 alone, (7) Ren lon alone, and (8) a Null susceptible genotype. QTL combinations were inoculated with 0, 2300, or 5000 reniform nematodes per 120 cm 3 soil in growth chamber tests. Plants were harvested at 60 days after inoculation, plant growth measurements made, and the nematode reproduction factor calculated. In this study, the Ren barb1 genotype was scored as susceptible to reniform nematode. Combining Ren lon with Ren barb2 did not improve resistance to reniform nematode; however, the Ren barb2 /Ren lon combination showed improved growth compared to LONREN-1, BARBREN-713, and the susceptible null check.