Improving the use of rye (Secale cereale) for nematode management:: potential to select cultivars based on Meloidogyne incognita host status and benzoxazinoid content

Six geographically diverse cultivars of rye (Secale cereale), a wheat (Triticum aestivum) cultivar and hairy vetch (Vicia villosa) cultivar unstated were screened for Meloidogyne incognita host suitability. Chemical constituents of rye can suppress M. incognita, so the rye cultivars and wheat were also tested for benzoxazinoid content to determine if rye cultivar selection could be based upon plant chemistry. There was variation in M. incognita host status among the rye cultivars. Cultivars Aroostook, Elbon, Oklon and Wrens Abruzzi were the most resistant rye cultivars, with low numbers of M. incognita eggs/g dry root. Cultivar Wheeler had somewhat more eggs/g root than these cultivars, while cv. Merced supported nearly three times more eggs/g root than cv. Wheeler. Most of the rye cultivars were similar to each other in total benzoxazinoid content, although cv. Aroostook had the lowest amount of total benzoxazinoids. When data from roots and shoots were combined, more than 79% of the total benzoxazinoids in all six of the rye cultivars were comprised of the non-methoxy-substituted forms: i) (2R)-2-beta-D-glucopyranosyloxy-4-hydroxy-(2H)1,4-benzoxazin-3(4H)-one (DIBOA-glucoside); ii) 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA); and iii) benzoxazolin-2(3H)-one (BOA). In the rye cultivar roots there was little difference among cultivars in amounts of the methoxy-substituted benzoxazinoids: i) (2R)-2-beta-D-glucopyranosyloxy-4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA-glucoside); ii) 2,4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA); iii) 6-methoxy-benzoxazolin-2(3H) -one (MBOA); and iv) 2hydroxy-7-methoxy-(2H)-1,4,-benzoxazzin-3(4H)-one (HMBOA). However, cv. Aroostook roots had the lowest concentration of nonmethoxy-substituted benzoxazinoids. Rye cultivars were generally similar to each other in amounts of benzoxazinoids in shoots. The shoots had much lower concentrations of methoxy-substituted benzoxazinoinds than the roots but much higher concentrations of nonmethoxy-substituted forms. Cultivars with the lowest numbers of eggs/g root and the highest amounts of benzoxazinoids (with potential for action against nematodes in soil after incorporation as a green manure) are possible candidates for optimal nematode management.