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Ha dinh Tuan. 2012. Etiology of sugarcane ratoon stunt disease in Southeast Vietnam and management. PhD Thesis. Nong Lam University. Vietnam.
Thứ ba, 28-08-2012 | 09:59:51

Address: Sugarcane Research Institute, Ben Cat, Binh Duong, Vietnam.

 

ABSTRACT

The study aims at determining the pathogen causing ratoon stunt disease (RSD) via morphological, biochemical and molecular properties, and suggesting the appropriate management especially in seed multiplication.

In SC medium plus nalidixic acid at 10µg/ml, the colony diameters obtained 0.19 mm (varied from 0.09 mm to 0.30 mm) withouth pigment or with lightly white colour.Catalase reaction was positive but negative oxydase and red methyl reactions. Bacteria did not produce H2S, not decompse urea and not hydrolyse starch. It belongs to positive gram bacteria with rod shape, pleomorphism. The bacteria size was 0.37-0.48 µm x 1.1-1.8 µm. Its cells represented of V/Y typical shape of Coryneform group. Koch’s postulate pinpointed their characteristics of RSD bateria Leifsonia xyli subsp xyli. Accordingly, amplification of 16S-23S rRNA of genomic DNAs of isolates collected in Southeast Vietnam obtained PCR product of 438 bp and 392 bp by using primers Cxx1/Cxx2 and primers Lx1, respectively. DNA sequence alignment indicated that highly homologous sequences between queries of 8 isolates and subjects from Genebank database.

According to the survey, the RSD became popular and well extended in sugarcane larde scale areas in Southeast Vietnam. Appromimately stalk weight lossed 22.66% due to RSD. In term of serious infestation, sugarcane yield loss could reach 46.19%. It depended on sugarcane type of plant cane or ratoon, various genotypes. However, it did not depend on new or old varieties, which have been grown for a longterm culture.

Cutting practice affected to the disease transmission. Knife used to cut sugarcane, which was infested RSD, could transmit it at 15 subsequent cuts with the same knife. If the infection was more serious, the worse and longer transmission, but not clear at the 25th cut. The RSD did not influence sugar quality in the 3rd season of sugarcane.

Yield loss could be 18.04% and 33.58% in plant cane and ratoon, respectively, under rainfed condition. The loss could be 5,00% and 10,61% in plant cane and ratoon, respectively, under irrigated condition. Supplemented irrigation of 3-5 times with 200 m3 water / ha / one could enhance the better plantcane’s funtional vessels, high tillering, better canopy, higher stalk yield, and reduced RSD influences.

Hot water treatment of cutting stems was recommended at 50.50C for two hours to prevent from the RSD, to enhance funtional vessels highly activated and to stabilize sugarcane yield at both plantcane and ratoon. The treatment helped functional vessels activate with 98.6% and 99.4% higher rate than check in the 1st season under rainy condition and in the 2nd one under supplemental irrigation; respectively. This gained higher propagation rate of 12.3 and 11.8 times as compared to check, in the early rainy season and the end of rainy one under irrigation, respectively.

 

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