Abstract
Levels of resistance to the root-knot nematode Meloidogyne arenaria in F2 individuals from the second, third, and fourth backcross (BC) generations were compared in seven separate tests to that of the root-knot nematode-resistant peanut germplasm line TxAG-7. Resistance of TxAG-7 was derived from the wild species Arachis batizocoi, A. cardenasii, and A. diogoi. Recurrent susceptible parents were Florunner and Tamnut 74 for the all backcrosses, Tamspan 90 for BC3 and BC4, and NC 7 and VC-1 for BC4. Resistance in these tests was defined as an inhibition of nematode reproduction relative to that of the susceptible recurrent parent. Numerous individuals with a level of resistance similar to that of TxAG-7 were identified from each backcross generation. In three field tests, the resistant BC2 genotype TP-223 supported a lower final nematode population density than did its susceptible recurrent parent Florunner. When rooted cuttings from selected BC4F2 individuals were retested to confirm the original resistance class, ratings were unchanged for those originally identified as resistant or susceptible. Of nine individuals originally identified as having moderate resistance (2.5 to 12.5% of the eggs/g roots as the susceptible recurrent parent), one was identified as susceptible, one as moderately resistant, and seven as resistant (<2.5% of the eggs/g roots) upon retest. These data are evidence that this source of resistance is readily recoverable from advanced back-cross generations.
Potentials of potassium humate, ammonium humate, and vermicompost tea in controlling root-knot nematode, Meloidogyne arenaria and improving biochemical components in eggplant
