Effect of inoculum concentration, wetness duration and plant age on disease development by Exserohilum prolatum in itchgrass (Rottboellia cochinchinensis)

Exserohilum prolatum, a fungus isolated from diseased itchgrass plants in Peninsular Malaysia, has been considered as a potential agent for biological control of this serious grass weed. Inoculum concentration, wetness duration and itchgrass age significantly influenced disease development by E. prolatum in itchgrass when evaluated in glasshouse experiments. Disease development increased with increasing inoculum concentration from 2x104 to 2x107 conidia/ml. As wetness duration increased, disease development increased. Complete kill of itchgrass at 3 to 4 leaf stage was obtained at 2x106 conidia/ml and a 24 hr dew period. However, when formulated in 0.01% Tween 20 and 2% palm oil, E. prolatum reduced wetness duration requirement, and exposure to 12 hr dew period resulted in 80% reduction in itchgrass shoot dry weight. Susceptibility of itchgrass to the fungus decreased with increasing plant age. Itchgrass at two to six leaf stages were the most susceptible to fungus infection. يعتبر فطر(Exserohilum prolatum)  والذي تم عزله من عشبة أم بليلة في شبه جزيرة ماليزيا وسيلة مكافحة إحيائية فاعلة لهذه العشبة النجيلية الضارة. عوامل تركيز اللقاح ، فترة الرطوبة وعمر النبات أثرت معنوياً على تطور المرض بواسطة (E. prolatum) في عشبة أم بليلة عندما قيّمت بتجارب داخل صوبة زجاجية. وقد تلاحظ أن تطور المرض قد إرتفع إرتفاعاً معنوياً مع إرتفاع معدل تركيز اللقاح منx 2  104 وإلى 2 x 107 كونيديا/مل. من ناحية أخرى تلاحظ أن شدة الإصابة بالمرض إزدادات معنوياً بإزدياد فترة الرطوبة. هذا وقد حدت موت كلي للعشبة عمر 2-3 ورقات عندما تمت معاملتها بواسطة تركيز لقاح 2x106 كونيديا/مل وفترة رطوبة 24 ساعة. أدى إستخدام عامل إنتشار Tween 20 بنسبة 0.01% وزيت النخيل بنسبة 2% إلى تقليص الحاجة إلى فترة رطوبة ممتدة (24 ساعة) حيث إنخفض الوزن الجاف للمجموع الخضري بنسبة 80% عند معاملة العشبة بفترة رطوبة بلغت 12 ساعة. أبانت النتائج أن قابلية العشبة للإصابة بالفطر قد إنخفضت مع تقدم عمر النبات وأن الأعشاب عمر 2-6 ورقات كانت أكثر قابلية للإصابة

Gene flow from Clearfield® rice to weedy rice under field conditions

Imidazolinone-herbicide-resistant Clearfield® (CL) rice permits the selective chemical control of weedy rice (Oryza sativa), a major weed problem in South-East Asian rice growing countries. However, there is major concern involving resistant individuals resulting from gene flow as the cultivated and weedy rice live side by side in the fields. An experiment was conducted in the rice fields of Kuala Rompin, Pahang, Malaysia to determine which Clearfield® rice cultivars and weedy rice cultivars are more prone to hybridization, and the effect on distance between the pollen donor and receptor plants. The experiment was piloted in a split plot design with four replications. Encircled population technique was used to determine the distance between the Clearfield® rice and detection of hybrids (F1). Resistance of progeny was determined after spraying with OnDuty™ and the confirmation of hybrids was done using the SSR primer RM251. Higher survival rate was recorded with cv. CL2 which was significantly different from cv. CL1. Weedy rice cultivar V1 and V2 in CL1 plots differed significantly from the same cultivar from CL2 plots. However, no significant difference was observed between weedy rice cultivars of V3 and V4, either in CL1 or CL2 plots. No survivors were found after second spraying. Suspected hybrids were found up to 5 m however the rate was much lower compared to only 1 m from the CL plots

Phytotoxic interference of volatile organic compounds and water extracts of Tinospora tuberculata Beumee on growth of weeds in rice fields

Tinospora tuberculata Beumee is an aromatic shrub with pharmacological properties and belongs to the Menispermaceae family. We assessed T. tuberculata for its ability to suppress growth of weeds in rice fields. In seedling bioassays, the rate of seed germination and the radicle and hypocotyl lengths of barnyard grass, rice and weedy rice seedlings were reduced as the concentration of aqueous water extracts and volatile organic compounds increased compared to the control. In a glasshouse experiment, T. tuberculata leaf powder also exhibited effective reduction in the emergence and growth of weeds in rice fields. Applications at rates of 4 t ha−1 completely suppressed emergence of barnyard grass, sprangletop and smallflower umbrella. The chemical compositions of extracts and volatiles were analyzed by GC–MS and HS-SPME-GC–MS. The results showed that 7 of 43 components in the leaf aqueous extract, as compared to 5 of 15 compounds in the stem aqueous extract, are known to be toxic compounds. Moreover, eight main volatile organic compounds were identified, which accounted for 97 and 95% of the whole fresh and dry leaf volatiles, respectively. We observed qualitative and quantitative differences in the compounds present in the dry and fresh leaf. Confocal laser scanning microscope images showed that the volatile emissions and aqueous extracts also inhibited the main root diameter, and the number and elongation of root hairs of tested weeds in rice fields. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors. Hence, it can be used as a mulch to suppress weeds in rice fields and for developing new herbicide based on phytotoxic compounds release by this plant

Evaluation of bioherbicide for controlling weedy rice and enhancing the yield of rice in Malaysia

Aim: Rice (Oryza sativa L.) is the second most important food crop in Malaysia, and weedy rice is the severe constraint in the Malaysian rice field. An experiment was conducted in Shadehouse at Field 2, Universiti Putra Malaysia to assess the performance of Agroplus BioDcomposer as a bioherbicide to control weedy rice and to select appropriate dosage of Agroplus BioDcomposer for effective control of weedy rice in the rice field. Methodology: Ten treatments of herbicides were applied in the experiment viz., control (0 ml), Agroplus BioDcomposer® (150 ml 20 l-1 water, 300 ml 20 l-1 water and 450 ml 20 l-1 water), Paraquat (125 ml 20 l-1 water, 250 ml 20 l-1 water and 375 ml 20 l-1 water) and the combination of Agroplus BioDcomposer® with Paraquat @150 ml 20 l-1 water + @125 ml 20 l-1 water, 300 ml 20 l-1 water + 250 ml 20 l-1 water and 450 ml 20 l-1 water+375 ml 20 l-1 water). Data on the percentage of weedy rice killed three days after treatments and percentage of weedy rice emergence 7 and 14 days after soil application of treatments were recorded to evaluate the efficacy of different treatments. Results: The results revealed significant differences among treatments in the percentage of weedy rice killed, weedy rice emergence after treatments application and the ultimate yield of rice. Paraquat, @ 375 ml 20 l-1 water and a combination of Agroplus BioDcomposer® and Paraquat (300 ml 20 l-1 water + 250 ml 20 l-1 water) performed better over other treatments to kill the weedy rice, to control the emergence of weedy rice from the seed bank and produced the highest rice yield. Interpretation: The overall result revealed that the recommended rate of Agroplus BioDcomposer® + Paraquat (300 ml 20 l-1 water + 250 ml 20 l-1 water) is more appropriate and suitable for environmental friendly control of weedy rice in Malaysia

Studies on some biological aspects, competitive ability and chemical control of Bermudagrass (Cynodon dactylon (L.) Pers.)

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN014051 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Study on resistant biotypes of Echinochloa crus-galli in Malaysia

Present study was carried out to identify resistant biotypes of Echinochloa crus-galli and to determine their control measures by application of herbicides. Propanil, quinclorac and cyhalofop-butyl was tested against 10 populations of Echinochloa crus-galli which was collected from rice fields of Kedah, Malaysia. Weed populations such as KPT, SB1, SB2, KPE, SY, TD, DB, KB1 and KB2 was identified as resistant biotypes and only KP population recorded as susceptible biotype to propanil. Out of 10 populations, only KB1 was found resistant biotypes and all others identified as susceptible to quinclorac. Weed populations of KP, KPT, SB1, KPE, SY and KB2 was found susceptible while SB2, TD and KB1 identified as resistant biotypes to Cyhalofop-butyl. Among 10 tested populations, only KB1 was found resistant biotype to propanil, quinclorac and cyhalofop-butyl. The ED(50) values from the dose-response experiments indicated that the resistant biotype was >four times resistant to propanil, >10 times resistant to quinclorac and >17 times resistant to cyhalofop-butyl, respectively than susceptible biotype. Resistant biotype KB1 was controlled by combined application of quinclorac and propanil at rates of 0.30 and 5.50 and kg a.i. ha(-1) or quinclorac and cyhalofop-butyl at rates of 0.30 and 0.80 kg a.i. ha(-1), respectively

Gene flow from Clearfield® rice to weedy rice under field conditions

Imidazolinone-herbicide-resistant Clearfield® (CL) rice permits the selective chemical control of weedy rice (Oryza sativa), a major weed problem in South-East Asian rice growing countries. However, there is major concern involving resistant individuals resulting from gene flow as the cultivated and weedy rice live side by side in the fields. An experiment was conducted in the rice fields of Kuala Rompin, Pahang, Malaysia to determine which Clearfield® rice cultivars and weedy rice cultivars are more prone to hybridization, and the effect on distance between the pollen donor and receptor plants. The experiment was piloted in a split plot design with four replications. Encircled population technique was used to determine the distance between the Clearfield® rice and detection of hybrids (F1). Resistance of progeny was determined after spraying with OnDuty™ and the confirmation of hybrids was done using the SSR primer RM251. Higher survival rate was recorded with cv. CL2 which was significantly different from cv. CL1. Weedy rice cultivar V1 and V2 in CL1 plots differed significantly from the same cultivar from CL2 plots. However, no significant difference was observed between weedy rice cultivars of V3 and V4, either in CL1 or CL2 plots. No survivors were found after second spraying. Suspected hybrids were found up to 5 m however the rate was much lower compared to only 1 m from the CL plots

Phytotoxic interference of volatile organic compounds and water extracts of Tinospora tuberculata Beumee on growth of weeds in rice fields

Tinospora tuberculata Beumee is an aromatic shrub with pharmacological properties and belongs to the Menispermaceae family. We assessed T. tuberculata for its ability to suppress growth of weeds in rice fields. In seedling bioassays, the rate of seed germination and the radicle and hypocotyl lengths of barnyard grass, rice and weedy rice seedlings were reduced as the concentration of aqueous water extracts and volatile organic compounds increased compared to the control. In a glasshouse experiment, T. tuberculata leaf powder also exhibited effective reduction in the emergence and growth of weeds in rice fields. Applications at rates of 4 t ha−1 completely suppressed emergence of barnyard grass, sprangletop and smallflower umbrella. The chemical compositions of extracts and volatiles were analyzed by GC–MS and HS-SPME-GC–MS. The results showed that 7 of 43 components in the leaf aqueous extract, as compared to 5 of 15 compounds in the stem aqueous extract, are known to be toxic compounds. Moreover, eight main volatile organic compounds were identified, which accounted for 97 and 95% of the whole fresh and dry leaf volatiles, respectively. We observed qualitative and quantitative differences in the compounds present in the dry and fresh leaf. Confocal laser scanning microscope images showed that the volatile emissions and aqueous extracts also inhibited the main root diameter, and the number and elongation of root hairs of tested weeds in rice fields. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors. Hence, it can be used as a mulch to suppress weeds in rice fields and for developing new herbicide based on phytotoxic compounds release by this plant