| dc.description.abstract | Reniform nematode, Rotylenchulus reniformis, is a highly detrimental pest in cotton and necessitates improved understanding of both in-season detection and modern management options. Newly released genetically resistant varieties have proven to be a more consistent management option than traditional nematicides to maintain yields while simultaneously suppressing reniform nematode (REN) populations. However, knowledge is lacking to inform producers when to prioritize nematode resistance over industry-leading susceptible varieties relative to nematode pressure and production environment. Trials were conducted at College Station, Wall, and Lubbock, TX with objectives to evaluate variety performance across a wide range of environments and to delineate between abiotic and biotic plant stress like nitrogen and water availability, using in-season remote measurements. In variety evaluations, two REN varieties were compared to four reniform-susceptible industry-leading varieties in the respective regions. In remote measurement trials, PHY 443 W3FE (resistant) was compared to PHY 480 W3FE (susceptible) under different irrigation regimes and fertilizer N rates to induce abiotic stress similar to reniform nematode stress. Across all site-years, resistant varieties increased lint yields by 51% compared to susceptible varieties (p <.0001), and suppressed nematode densities by 53% (p <.0001). Plant heights were affected by variety in both irrigation regimes at College Station and Wall rainfed trials, where resistant varieties were consistently taller than susceptible varieties and had larger canopy percentages. Green-Red Vegetation Index (GRVI) values indicated that in dryland systems the resistant variety was greener but in irrigated systems nitrogen influenced GRVI and the susceptible variety was greener. Reniform nematode resistant varieties resulted in greater yield gains in irrigated systems with large reniform nematode populations but at all site years genetic resistance improved lint yields and suppressed nematode populations. GRVI was not a consistent indicator of reniform nematode stress but did correlate consistently with fertilizer N rate in irrigated trials. Within irrigation regimes, plant height and canopy percentage were consistently correlated with reniform nematode stress and are likely the most useful remote measurements to estimate in-field nematode distribution and severity. | |
