Study On Weediness Characteristics And Allelopathic Potential Of Weedy Rice (Oryza Sativa L.) And Competitive Relation With Cultivated Rice (O. Sativa L.)

In this paper weedy rice populations collected from different areas of Jiangsu province were taken as the study subjects and two cultivated rice varieties as contrast materials to stuy its weediness characterizations, the allelopathy potential and competition with cultivated rice.The weediness characteristics of twelve weedy rice samples were studies, compared with those of two cultivated rice samples in Jiangsu province. The results showed that the plant height of weedy rice populations in Jiangsu province varied from 68.51 to 122.34 cm, which was lower than that of cultivated rice, and and the tillering ability is stronger than the cultivated rice, whose tillering number is much more than cultivated rice. On the aspect of ear characteristic, the length of ear is shorter, the ear is loose and effective ear is fewer; part of weedy rice has elymusbrejaristatus, red peel and lower fruiting rate, its grain type is between hsien rice and japonica rice whose dry weight is small; also the seeds have different dormancy. Weedy rice has earlier heading date and the differentiation date, stronger shattering property and shorter life cycle than those of cultivated rice.In order to find out the differences in germination characteristics of different biotypes of the weedy rice in Jiangsu area, six biotypes of weedy rice and two cultivated rice varieties from southern, middle and northern Jiangsu area was selected to determine the effects of different environmental factors on their seed germination by seed bioassay, including temperature, water potential, salinity, pH, and burial depth. The results showed that on the condition of different temperature, the germination rates of weedy rice and cultivated rice were listed in sequence as follows:four biotypes of the weedy rice from southern, middle Jiangsu area>SY63>two biotypes of the weedy rice from nothern Jiangsu area>NJ44. On the condition of different Osmotic potential, the germination of rice is as follows in descending order:four biotypes of the weedy rice from southern, middle Jiangsu area> two biotypes of the weedy rice from nothern Jiangsu area> cultivated rice. On the condition of different NaCl concentration, germination of JT-3, WJ-2, JD-4 and FN-3 is greater than cultivated rice. In the interval 250 mM to 300 mM, the germination of GY-LZC and JY-1 is between two cultivated rice. As solution pH changes, germination of central and south of Jiangsu province has little change which is beyong 90%. When pH condition is unsuited to germinate, the germination in descending order is as follows:four biotypes of the weedy rice from southern, middle Jiangsu area> two biotypes of the weedy rice from nothern Jiangsu area> cultivated rice. On the aspect of buried depth, from 1 cm to 3 cm, the germination rate of weedy rice is larger than that of cultivated rice, while from 4 cm to 7 cm, the germination rate of cultivated rice is larger than weedy rice.The competitive effect between two weedy rice samples (WJ-2, GY-LZC) and two cultivated rice samples (SY63, NJ44) were studied by means of dewit's test. The result showed that when the total seed amount of sowing is fixed, the tillering and the leaf area is reduced evidently as the sowing of weedy rice is larger, while the plant height is also decreased but not obviously. The result of competition is as follows:On the aspect of tillering, two kinds of weedy rice is both larger than cultivated rice, on the aspect of plant height, GY-LZC is larger than cultivated rice while WJ-2 is smaller than SY63 and larger than NJ44, on the area of triple leaf behind, WJ-2 and GY-LZC is both smaller than SY63 and larger than NJ44.By using agar late sowing co-cultured method and leaf aqueous extracting, the allelochemical potential of thirty-two weedy rice samples and one weejk allelopathy potential rice were screened to compare allelopathy potential to Echinochloa crusgalli and lettuce of different materials And then the R1 obtained from soil culture and agar late sowing co-culturing were compared.. The result showed that weedy rice could inhibit plant height of E. crusgalli to some extent. The inhibition effect of WJ-4 and BH-1 increased with the increasing of density of weedy rice. The allelopathy potential of the same material to E. crusgalli and lettuce is different, in which lettuce is more susceptible. In soil culture test, weedy rice could inhibit E. crusgalli in the aspect of plant height and root length, and the R1 in soil culture is slightly larger than that in agar late sowing co-cultured method.