Resistance to Rotylenchulus reniformis and Meloidogyne incognita Race 3 in the Major Cotton Cultivars Planted Since 1950

Abstract

The southern root‐knot nematode, Meloidogyne incognita race 3 (Kofoid & White) Chitwood, and the reniform nematode, Rotylenchulus reniformis Linford & Oliveira, are the most widespread and economically important nematode pests of Upland cotton (Gossypium hirsutum L.) and Pima cotton (G. barbadense L.) in the USA. Progress in the development of nematode‐resistant cotton cultivars is unclear. Plant breeders often have selected for nematode tolerance by measuring cotton yield in nematode‐infested fields but seldom have selected for resistance by measuring nematode reproduction. The objective of this research was to measure nematode reproduction to assess progress in the development of nematode resistance in cotton. Fiftyfive Upland and four Pima cotton cultivars, comprising the most widely planted cultivars in the USA each decade since 1950, were evaluated in growth chambers for resistance to M. incognita and R. reniformis. The cultivar Deltapine 16 served as the susceptible and the germplasm line Auburn 623 RNR as the resistant control. Reproduction by M. incognita on the cultivars ranged from 4 to 294% of that on Deltapine 16. All cultivars were highly susceptible to R. reniformis. A small increase was detected in the general level of resistance to M. incognita between 1950 and 1996, but only the recently released cultivars, Stoneville ‘LA887’, Paymaster ‘1560’, and CPCSD ‘Acala Nem‐X’, showed consistently high resistance. These cultivars were developed by measuring nematode reproduction in pots or root galling in field plantings, as well as yield and related agronomic traits.

Development of AFLP and derived CAPS markers for root-knot nematode resistance in cotton

“…Robinson et al (1999) reported that Pima S-5, Pima S-6 and Pima S-7 were susceptible to root-knot nematode and that Pima S-2 was moderately resistant to root-knot nematode. However, in our tests, Pima S-2 was susceptible to root-knot nematode and had only slightly less infection than susceptible Pima S-7.…”

“…However, its root-knot nematode resistance status has not been reported. Most Coker lines except Coker 100W were reported to be susceptible to root-knot nematodes (Robinson et al 1999). Based on these breeding histories, the four genotypes with unknown phenotype are likely to be susceptible to root-knot nematodes.…”

A transgressive segregation factor (RKN2) in Gossypium barbadense for nematode resistance clusters with gene rkn1 in G. hirsutum

“…Pima cottons (G. barbadense L.) are good hosts for M. incognita (Robinson et al 1999), and in preliminary studies with interspeciWc Pima S-7 £ Acala NemX progenies, we observed some genotypes with levels of nematode resistance higher than the resistant parent indicating strong transgressive segregation and epistasis eVects on resistance. To further characterize the transgressive segregation for resistance in interspeciWc crosses of susceptible G. barbadense cv.…”

Relative Response of Four Tomato Species to <i>Rotylenchulus reniformis</i> Infestation

“…A susceptible control S. lycopersicum "Rutgers" (LA 1090) was included. This genotype has been shown to support prolific reproduction of reniform nematodes [21]. In all, six randomized replications of 40 genotypes were tested against R. reniformis.…”