Differential morphological and physiological responses of two oilseed Brassica species to a new herbicide ZJ0273 used in rapeseed fields

Weeds are considered as a major threat to the production of oilseed Brassica crops. The use of herbicides that are safe for crops and effective in controlling weeds is crucial for the agronomists and farmers. Propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), a derivative of 2-pyrimidinyloxy-N-aryl benzoate, is a new herbicide used in the rapeseed field. To evaluate the tolerance of Brassica species against this new herbicide, two cultivars of rapeseed Brassica napus cv. ZS 758 and Brassica rapa cv. Xiaoyoucai were tested by a foliar spray of ZJ0273 at the rate of 100, 500 and 1000 mg/L and a currently used ALS (acetolactate synthase)-inhibiting herbicide bispyribac-sodium (BS) at the rate of 100 mg/L. The results showed that both the cultivars of Brassica were less affected by ZJ0273 as compared to BS. Increasing level of ZJ0273 herbicide from 100 to 1000 mg/L increased the stress for the plants of both the cultivars as indicated by enhanced accumulation of malondialdehyde content. The activities of ALS and antioxidant enzymes (superoxide dismutase and peroxidase), soluble protein and sugar contents, photosynthetic system (SPAD value, photosynthetic rate and chlorophyll fluorescence) as well as the agronomic characters also declined consistently with each successive increase in ZJ0273 concentration. In general, the plants treated with 100 mg/L ZJ0273 recovered from the herbicide stress after 28 days. B. napus showed more tolerance than B. rapa to the new herbicide. Nevertheless, BS application at 100 mg/L did not allow the plants of both the cultivars to recover from the herbicidal stress.     

Histological study of giant cells formed by the root-knot nematodeMeloidogyne artiellia as compared withM. hapla andM. javanica in cabbage, turnip and barley

Feeding sites induced by the root-knot nematodeMeloidogyne artiellia in turnip (Brassica rapa), cabbage (Brassica oleracea) and barley (Hordeum vulgare) were examined by light and electron transmission microscopy, and compared with those formed byM. javanica andM. hapla. The feeding cells ofM. artiellia in turnip and cabbage showed hypertrophy, hyperplasia and vacuolization, and became multinucleate giant cells. In contrast to the typical simple-shaped giant cells ofM. javanica andM. hapla, those ofM. artiellia had an amoeboid structure containing ‘protuberances’, which are distinct from previously reported ‘projects’ of giant cells induced byM. incognita in other plants. Protuberances expanding between vascular cells were observed in young and developed giant cells. Since no cell-wall fragments were found at the bases of the protuberances, either by light or electron microscopy, it is strongly indicated that these structures were caused by local expansion of the giant cells rather than by fusion with adjacent cells. The giant cells ofM. artiellia in barley had regular shapes of giant cells without protuberances, and resembled those induced byM. javanica orM. hapla in turnip and cabbage. http://www.phytoparasitica.org posting Sept. 17, 2006.