ABSTRACT

Cotton (Gossypium hirsutum L.) production in the United States has been plagued for many years by root-knot nematodes (Meloidogyne incognita acrita) and the root-knot/fusarium wilt (Fusarium oxysporum) complex. In 1999, the estimated loss from nematodes was approximately 625,200 bales (3.53%) and from Fusarium wilt approximately 87,137 bales (0.45%) (Blasingame &Patel, 1999). A PhytoGen experimental cotton line, PH98M-3196, was derived from a cross with Stoneville LA 887 and it has the same level of root-knot resistance. PH98M-3196 is an early to medium maturity, semi-smooth leaf variety that has demonstrated good fiber quality and yielding abilities throughout the South. To fully understand the value of this level of root-knot resistance, 4 in-house trials were conducted in root-knot infested fields in different areas of the South where root-knot nematodes are considered to be a problem. These trials evaluated different nematicide treatments on PH98M-3196 and a root-knot susceptible check, PSC 355. For the Phytogen in-house trials, the main plot, nematicide, treatments were not significantly different at any location for lint yield, lint percentage or fiber quality traits; however, there were numeric differences for main plot effects at all locations for lint yield. As nematicide levels increased, lint yields increased. In Dumas only one sampling date was significant for main plot effect. In both locations however, the last 2 sampling dates were significant for split plot treatment, variety. PH98M-3196 had dramatically lower live root-knot nematodes larva counts than PSC 355. Under conditions where nematode populations reduce stand counts and suppress plant growth, planting of varieties with resistance to root-knot nematodes may allow for lower rates of nematicide to be applied. The ability of PH98M-3196 to suppress nematode populations seen in the present study may make it possible for growers to plant susceptible crops the following year since the initial root-knot levels the following year should be at a reduced level. Even a moderate level of resistance has demonstrated its ability to give some economic benefits to growers in allowing lower levels of nematicides to be used. Also, this level of resistance will provide growers with more crop rotation options that can further enhance profitability.