Rec.(l-ieloid.):l 



breeding; FDR RESISTANCE TO MELOITinGYNE SEP. 

 Albert L. Smith 



Historical 



The breeding for resistance to root-knot is historically significant. 

 Webber and Orton, in 1902, reported a root-knot resistant cowpea, the 

 Iron variety. This variety was also resistant to Fusarium, in which 

 they were interested, so that, accidentally, root-knot resistance was 

 discovered. This stimulated the search for root-knot resistance in 

 other crops. 



Importance 



Root-knot resistance breeding is of primary importance to the south- 

 eastern area for several reasons as follows: 



1. Primary plant parasitic nematode in the south, particu- 

 larly on tobacco and cotton, the major cash crops, as 

 well as a host of lesser crops, particularly vegetables. 



2. It is important in the initiation of the wilt disease of 

 cotton and has more recently been found important in 

 initiating or intensifying several other diseases. 



3. Impiovement in root-knot resistance may improve the 

 resistance of crops to other nematodes, Clayton has made 

 this observation in tobacco, and the writer believes the 

 same situation exists in the cotton crop. 



The several species of Meliodogyne, because of the wide host range and 

 the adaptability of this parasite to infest a wide range of soil tex- 

 tures, are considered the most important plant parasites in the south. 

 This wide range of adaptation to soil textures is illustrated by theii' 

 attack on the cotton crop. The general statement is made that the root 

 knot nematode is a problem in all the lighter soils from Virginia to 

 California. Going to the extreme, there are a few soils which are too 

 sandy for the survival of the root-knot nematode. These soils are 

 primarily near the coast in South Carolina and Georgia. Holdeman and 

 Graham have found areas in South Carolina where the sting nematode and 

 other ectoparasites are the primary parasites and where apparently the 

 soil is GOO sandy for root-knot. A small area of the Agronomy farm at 

 Auburn, which mechanical analysis shows is 80 per cent sand, is also 

 too coarse for root-knot survival and it is replaced by Tr ichororus , 

 Pratylenchus , and other ectoparasitic species. Although root-knot can 

 become serious in rather heavy soils, workers report an area on the 

 FCfq^oTiMcnt Station Farm in Louisiana where the kidncy-shapcd nematode, 



