Allelopathic potential of itchgrass (Rottboellia exaltata L. f.) powder incorporated into soil

Itchgrass ( Rottboellia exaltata L. f.) is a widespread weed in northern Thailand. The farmers in this area have been using itchgrass as a mulching material in order to control other weeds in vegetable fields. Laboratory experiments were undertaken to investigate the phytotoxic activity of itchgrass powder incorporated into soil in order to evaluate the allelopathic activity in the field. The phytotoxic activity on the growth of radish seedlings ( Raphanus sativa L. var. radicula ), used as a test plant, was more pronounced in the root than in the shoot growth. The phytotoxic activity was found to be similar for the soils incorporated with the shoot or the root powder of itchgrass. The growth of the radish seedlings grown in sea sand and watered with soil water obtained from the soil previously incorporated with itchgrass powder showed a similar inhibition to those planted in the treated soil. The phytotoxic activity on the growth of the radish seedlings in the soil incorporated with the powder decreased over time. It is suggested that itchgrass releases phytotoxic compound(s) into soil water and the concentration of the active compound(s) in the soil water decreases over time.     

Allelopathic effect of itchgrass (Rottboellia cochinchinensis) on seed germination and plant growth

Herbicides produce a wide range of toxic side-effects that pose a potential hazard to the environment. The development of natural allelochemicals is one method of addressing these issues. Here, we describe the allelopathic activity of itchgrass ( Rottboellia cochinchinensis ), which can inhibit the seed germination and growth of weeds. Farmers in Lampang, northern Thailand, have been cultivating itchgrass and using it as a mulching material to control other weeds in vegetable fields. It has long been observed that itchgrass interferes with the growth of other plants. This study showed that the density of weed species in the itchgrass-infested areas was lower than that in the itchgrass-uninfested areas. The shoot and root growth of Bidens pilosa , Mimosa pudica , Ageratum conyzoides , Echinochloa crus-galli , Oryza sativa var. RD 6, and Lactuca sativa var. OP were significantly reduced in soil previously planted with itchgrass. Water-soluble extracts from all parts of itchgrass had inhibitory effects on the growth of some test plants. Allelochemicals from itchgrass can inhibit seed germination and plant growth better at a 1 cm distance than at a 3 cm and 5 cm distance from itchgrass. Our results suggest that itchgrass has a strong competitive ability and possible allelopathic activity to other plant species. The allelopathic activity of itchgrass in the soil can influence the germination of adjacent species, causing reduced growth of seedlings.     

Glufosinate tolerance in hybrid corn varieties based on decreasing ammonia accumulation†

Field tolerance to glufosinate in hybrid corn varieties (non‐GMOs) was evaluated at physiological and biochemical levels. The present experiment was conducted to provide information for the development of a glufosinate‐tolerant corn variety through a conventional breeding program. The effect of glufosinate on the physiological response to crop injury, plant height, and fresh and dry weight was examined in 15 locally adapted corn varieties to this herbicide. The highest degree of tolerance was observed in the varieties Pacific 626 and Pacific 983, while the most susceptible variety was CP 989. CP 989 tended to accumulate ammonia more than Pacific 626 and 983; and the concentration of glufosinate resulting in a 50% increase in ammonia concentration in CP 989 was half that required for Pacific 626 and 983. These results indicate that the degree of ammonia accumulation might be related to the sensitivity of these corn varieties to glufosinate.