Twenty rice cultivars, including three genetically-distinct groups (japonica, indica-1, and indica-2), were evaluated for their response to inoculation with Azospirillum sp. strain B510 in paddy fields with standard nitrogen (SN) and low nitrogen (LN) fertilization. In the SN field, the tiller numbers in most indica-2 cultivars, 37 days after transplanting (DAT), were significantly increased by the B510 inoculation, whereas those in 4 japonica cultivars were significantly decreased. A similar growth response was observed in the LN field, although the impacts of the B510 inoculation were more varied than in the SN field. At 58 DAT, the tiller numbers in most cultivars were lower or unaffected by the B510 inoculation under both SN and LN conditions, except that the tiller number of the Nipponbare cultivar, which is classified as japonica, was significantly higher in the LN field only. These results suggest that the effects of inoculation with Azospirillum sp. strain B510 on the growth of rice plants, especially on tiller numbers at the early growth stage, vary depending on the rice genotype, as well as nitrogen level. Therefore, the plant genotypes, growth stages, and fertilization managements must be considered when a plant-associated bacterium is evaluated for beneficial effects under field conditions.
A reverse dot blot assay for identification of Pratylenchus spp. has been developed using specific oligonucleotides designed from the sequence of the internal transcribed spacer (ITS) region. The reverse dot blot is a technique which can be especially used for the simultaneous identification of various bacteria. The target fragment was amplified, and labelled with digoxigenine by a polymerase chain reaction (PCR). The amplified fragment was hybridised with the membrane-immobilised oligonucleotide and the hybridization was detected non-radioactively. By this assay, it was possible to identify P. penetrans, P. coffeae, P. vulnus, P. loosi, P. brachyurus, P. crenatus and P. zeae in a single hybridization. Identification rapide et fiable de Pratylenchus spp. a l'aide de l'hybridation retro dot blot - Une technique retro dot blot pour l'identification de Pratylenchus spp. a ete mise au point en utilisant des oligonucleotides specifiques derives de la sequence de l'espaceur transcrit interne (ITS). La technique dot blot est une technique qui peut etre specialement utilisee pour l'identification simultanee de nombreuses bacteries. Le fragment cible a ete amplifie et marque par la digoxigenine a l'aide de la reaction de polymerisation en chaine (PCR). Le fragment amplifie a ete hybride avec l'oligonucleotide immobilise par membrane et l'hybridation detectee non-radioactivement. Grace a cette technique, il a ete possible d'identifier P. penetrans, P. coffeae, P. vulnus, P. loosi, P. brachyurus, P. crenatus et P. zeae en une seule hybridation.
In order to assess the efficacy of Crotalaria juncea and C. spectabilis as trap crops against the soybean cyst nematode, Heterodera glycines, rates of hatching of H. glycines eggs in the root leachate, penetration into Crotalaria roots by H. glycines juveniles and their development in the roots, and the effects of planting these Crotalaria species on population density of H. glycines in soil were investigated. The rates of hatching of H. glycines eggs in the root leachates from C. juncea and C. spectabilis were significantly greater than the rates in distilled water and in the leachates from non-host plants. Stimulation of hatching by C. juncea was significantly greater than that by C. spectabilis and similar to that by the host plant, kidney bean. The number of second-stage juveniles that penetrated Crotalaria roots was similar to the number that penetrated soybean roots, but most of the second-stage juveniles in Crotalaria roots did not develop to an advanced stage of growth. The population density of H. glycines in soil in which Crotalaria had been planted decreased significantly compared with that in fallow soil (no plants) in both pot and field plot tests. The effect of planting C. juncea on reduction in population of the nematode in soil was generally greater than that of C. spectabilis. From the results of these experiments, it was concluded that the use of Crotalaria, especially C. juncea, as a trap crop is a promising method for reducing the population density of H. glycines.
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