**2. Lipids**

**Host Common Name Host Scientific Name Use**

6 Soybean - Pest Resistance

small flowered buttercress *Cardamine parviflora* weed

Siberian pea tree *Caragana arborescens* ornamental sicklepod *Cassia tora* weed

soybean *Glycine max* edible Spanish broom *Spartium junceum* ornamental speedwell *Veronica peregrine* weed spider flower *Cleome spinosa* ornamental spotted burclover *Medicago arabica* forage stinking clover *Cleome serrulata* weed sweet clover *Melilotus taurica* weed sweet pearl lupine *Lupinus mutabilis* edible

tiny vetch *Vicia hirsute* ornamental vine white horsehound *Marrubium vulgare* medicinal plant white lupine *Lupinus albus* livestock feed white pea *Lathyrus ochrus* wild flower Wilcox penstemon *Penstemon wilcoxi* wilflower winged pigweed *Cycloloma atriplicifolia* weed yellow lupine *Lupinus lateus* wild flower

**Table 1.** Common names for plants that have been identified as good hosts for soybean cyst nematode [24-31].

requirements for these organisms are more extensive than what is currently known.

In many ways, it is inappropriate to compare humans to nematodes. But, from a nutritional perspective, much more is known about human nutrition than what is known about nutritional requirements of nematodes. For humans, numerous biochemical and mineral components are essential nutrients. But, for nematodes, only a few are known. Yet, nematodes have a compa‐ ratively simple digestive system. So, it would be reasonable to predict that nutritional

It is also inappropriate to generalize nutritional needs from studies on one nematode to all the nematodes within the various trophic categories. Certainly there should be similarities, but it is clear from the literature that animal parasitic nematodes have different needs from the plant parasites. And, it may also be that those plant parasites infecting specific organisms, such as SCN might have nutritional needs that synergize with the contents of the host soybean plant.

Survival is best understood when chemically defined culture media can be shown to not only sustain life, but also to promote reproduction. Chemically defined media have been identified for the survival of some nematodes and this work has recently been reviewed [34]. The

Lipids consist of many non-water soluble components including free fatty acids, phospholi‐ pids, triglycerides, sterols, and other species. Many of these classes have been studied at least in one host-nematode relationship and are the most studied with the exception of nucleic acids due to their great structural variety and importance as food reserves. For example, Krusberg [38] reported the total lipids and fatty acids from 5 species of plant parasitic nematodes, and their common hosts. They found that the nematodes had the same fatty acids as the hosts, with the exception of the polyunsaturated fatty acids. These appeared to be synthesized by the nematodes. There was also some speculation that nematode fatty acid synthesis resembled that of bacterial pathways rather than that of higher animals. It was not clear from the study whether intestinal flora of the nematode could have been at least partially responsible for this difference, or whether the nematode itself synthesized the fatty acids. Some nematodes are clearly capable of synthesizing longer chain fatty acids from shorter chain precursors. They are also capable of desaturating the fatty acids [39].

Entomopathogenic nematodes infecting locusts consume host fat and protein [40]. A decrease in lipid reserves has been seen in starved nematodes which can be related to decreased infectivity [41]. Lipid content is also known to decrease when nematodes come out of anhy‐ drobiosis [42]. Lipids associated with the nematode surface [cuticle] are triacylglycerols, sterols, specific phospholipids, and other glycolipids [43-45].

The most widely known class of essential nutrients for nematodes is sterol [36,46]. This nutritional requirement was first discovered by Dutky et al. [47] and thought to be potentially a means for control of plant parasitic nematodes. A recent review further confirms this nutritional sterol requirement for the nematode *C. elegans* [48]. Nematode parasites of animals also require sterol for larval development [49]. The biochemical mechanism which converts sitosterol to cholesterol appears to be lacking in nematodes [50]. Nematodes are capable of modifying sterols obtained from their diet [46] but degradation of sterols to CO2 by nematodes is not clear [51]. More than 63 sterols have been identified from free-living and plant-parasitic nematodes. Characteristics of sterols which can be used by nematodes include those which have a hydroxyl group at C-3, a trans-A/B ring system and an intact nonhydroxylated side chain but lack methyl groups at C-4 [52]. Plant sterols are different than animal sterols with plants being unique in methyl, ethyl or related alkyl groups at the C-24 position of the sterol side chain [52]. There are also differences between plant sterols and plant-parasitic nematode sterols. These findings suggest that nematodes ingest plant sterols and remove the C-24 side chain. In addition, the nematode saturates the double bonds in the four-membered ring system to produce stannols [52]. Steroid hormones are important in development processes and in transition to different life stages [53]. Most likely genetic and biochemical methods will be needed to determine the function of hormones found in nematodes [54]. Novel genes involved in the production of 17β-hydroxysteroid dehydrogenase in the soybean cyst nematode have been reported [55].

**4. Vitamins**

**5. Minerals**

**6. Carbohydrates**

population.

survival [79].

essential nutrients of *C. elegans* [66-68].

and supplement requirements across all nematodes.

There are 13 essential vitamins required by humans. These include Vitamin A [Retinol] Vitamin B1 [Thiamine] Vitamin C [Ascorbic acid] Vitamin D [Calciferol] Vitamin B2 [Ribofla‐ vin] Vitamin E [Tocopherol] Vitamin B12 [Cobalamins] Vitamin K1 [Phylloquinone] Vitamin B5 [Pantothenic acid] Vitamin B7 [Biotin] Vitamin B6 [Pyridoxine] Vitamin B3 [Niacin] Vitamin B9 [Folic acid]. Of these, vitamin E is known to be a nutritional requirement for the gastroin‐ testinal parasite, *Heligmosomoides bakeri* [65], and several of the B vitamins are known to be

Nutritional Requirements of Soybean Cyst Nematodes

http://dx.doi.org/10.5772/54247

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For SCN, DNA sequences responsible for the biosynthesis of enzymes that can produce some of the B vitamins *de novo* have been discovered [69]. Therefore, SCN may not need the same B vitamins as *H. bakeri*, for example. And, it is likely that there are other differences in vitamin

Considerable research on mineral requirements for nematodes has been reported in mamma‐ lian parasites. For example, the gastrointestinal nematode, *H. bakeri*, requires boron [70], zinc [71], and selenium [65] for survival. And, other nematodes have similar mineral requirements [72-74]. For example, magnesium, sodium, potassium, manganese, calcium and copper are required nutrients of *C. elegans* [5]. However, SCN mineral requirements remain unclear.

Whether minerals, influence nematode survival may not help in their control if necessary minerals are readily available in soil, and essential to the host organisms. But, elements not essential to survival of the host could be controlled in soils to help control SCN survival.

Nematodes require carbohydrates for energy, usually in the form of glycogen. One study showed that several different carbohydrates were sufficient to provide a carbon, or energy source for *C. elegans*, and that glucose was more effective than fructose or sucrose [76]. For *C. elegans*, glucose along with cytochrome c and β-sitosterol were sufficient to sustain a healthy

One of the most striking features of soybean chemistry is the abundance of pinitol [77-79]. Pinitol is a carbohydrate with unusual nutritional properties [77]. Figure 2 shows a total ion chromatogram of a derivatized extract of soybean roots. It is unusual for a plant to have so much pinitol. The levels shown in this study indicate pinitol is present at a concentration of 26 mg/g (dry weight) compared to peanuts with only 4.7 mg/g or clover with 14 mg/g [79]. However, there is no evidence that pinitol, or any of the related inositols are needed for SCN

Sterols were first reported in soy oil by Kraybill et al. [56]. Formononetin is an o-methylisoflavone mainly produced in legumes, including soybean plants [57]. It helps stimulate the production of steroids in mammals, and possibly also in nematodes. Research in this area by the USDA was reviewed by Chitwood [58].
