Response of root-knot nematode (Meloidogyne incognita) and saponin content of quinoa (Chenopodium quinoa)
Soltani, N., E. C. Bernard, and K. D. Gwinn.  2019.  Phytopathology.  (in press)

Demand for quinoa (Chenopodium quinoa) is increasing due to its high nutritional content and lack of gluten. In order to reduce costs associated with removal of saponins, sweet varieties (low saponin) are being developed; however, little is known about impact of saponin on resistance to plant pathogens. The objective of this research was to determine if saponin levels in quinoa predict plant response to root-knot nematode (RKN - Meloidogyne incognita). Eggs (2100 per plant) served as inoculum. Three cultivars (9 plants per variety) were inoculated: ‘Jesse’ (sweet); ‘Redhead’ (high saponin); and QQ74 (moderate saponin). After 28 d, roots were washed and weighed, and galls were counted. Numbers of galls/g root were approximately 3.5× greater in ‘Jesse’ and QQ74 than in ‘Redhead’ (P<0.05). Root mass was greater for ‘Redhead’ than the other two varieties, which did not differ. In a separate experiment, mobility of second stage juveniles (J2s) in aqueous extracts from uninoculated plants was tested. Oven-dried roots were autoclaved (15 mg/ml water), stored at room temperature (24 h), filtered, then re-autoclaved. Freshly hatched J2s were more sensitive to extracts from 'Jesse’ than to extracts from ‘Redhead’ or QQ74 (P<0.05). Since extracts did not foam when shaken, it is unlikely that bioactivity is due to saponins; therefore, other anti-nematodal compounds in roots may contribute to RKN tolerance. Further research is needed to fully understand tolerance in quinoa.