Abstract.

Two sources of reniform nematode (Rotylenchulus reniformis) resistance in two Upland cotton (Gossypium hirsutum) developed from related cotton species, BARBREN-713 (Renl̳o̳n̳1̳ and Renl̳o̳n̳2̳ genes), and the LONREN germplasm lines (Renl̳o̳n̳ gene) are available to breeders. Stunting was observed in the LONREN source of resistance, but not for BARBREN. To investigate future use of LONREN germplasm, lines were developed with different combinations of genes from both the LONREN and BARBREN-713 germplasm lines. Marker assisted selection (MAS) was conducted identify these gene combinations within breeding population 1) Renb̳a̳r̳b̳1̳ +Renb̳a̳b̳r̳2̳ 2) Renb̳a̳r̳b̳1̳ + Renb̳a̳r̳2̳ + Renl̳o̳n̳ 3) Renb̳a̳r̳b̳2̳ + Renl̳o̳n̳ 4) Renb̳a̳r̳b̳2̳ 5) Renb̳a̳r̳b̳1̳ 6) Renb̳a̳r̳b̳1̳+Renl̳o̳n̳ 7) Renl̳o̳n̳ , and 8) a susceptible genotype. Two populations were identified and increased in 2015. Genotypes were inoculated with 0, 2300, or 5000 reniform nematodes. Seedlings were harvested at 90 days to collect plant measurements and RF of reniform nematodes from roots and soil. The Renbarb1 genotype was susceptible. No significant differences in genotypes were observed for root and shoot measurements, and there was no indication of stunting.

Reniform nematode (Rotylenchulus reniformis Linford and Oliveira) currently infests about 36% of the Mississippi G. hirsutum acres causing economic losses of $130 million annually. For more than 40 years nematodes, including R. reniformis, have been managed using an at-planting treatment of Temik 15G or with soil fumigants like Telone II. With the label loss of Temik 15G and expense of soil fumigants, there is a need to develop an integrated nematode management program centered around nematicide seed treatments (NST) with and without foliar applications of Vydate C-LV. In addition there is a need to better understand how new cotton cultivars provide improved growth, development and yield in nematode infested fields. Results from research at Auburn and Mississippi State Universities revealed tested varieties responded positively to NST and improved growth and yield without NST was variety specific especially early in G. hirsutum development (between nodes 1-9). Cutivars Phy 499, FM 1740 and Stv 5458 showed the greatest nematode tolerance while Phy 375 WRF had the least tolerance, benefitting greatly from NST. Trials involving NST with and without Vydate C-LV indicated yield of plants treated with Temik 15G was greater than plants treated with NST treatments. Aeris + Votivo with and without Vydate C-LV provided better plant growth and yield than Aeris alone or with Vydate C-LV. Relative to yield Vydate C-LV treatments increased pounds of lint cotton/acre across all treatments. There were no differences in fruit retention at fruiting site one during the square period with fruit loss primarily occurring between bloom and open boll. Vydate C-LV treatments increased overall fruit retention compared to all nematicide seed treatments making them comparable to Temik 15G.

The reniform nematode is a major pest affecting common upland cotton in the United States. Management of this pest in cotton fields only gives partial control and is sometimes neither economical nor profitable. Past research has shown no resistance to the reniform nematode in currently available commercial cotton cultivars. Screenings of several currently available cotton cultivars for tolerance to the reniform nematode were conducted in the growing seasons of 2006 and 2007 at the Delta Branch Experiment Station in Stoneville MS. Several cultivars were identified as tolerant and productive including 'Croplan Genetics 3520 B2RF, ' 'DynaGrow 2520 B2RF, ' and 'Stoneville 5242 BR.' Other cultivars were tolerant but less productive, including 'Deltapine 488 BG/RR, ' 'Fibermax 960 B2R, ' and 'Stoneville 5599 BR.' 'Deltapine 455 BG/RR, ' 'Phytogen 370,' and 'Phytogen 485' were shown to be productive, but not tolerant to the reniform nematode.