Kyushu Plant Protection Research

A comparison of the biochemical, physiological and patliological characteristics of Burkholderia plantarii and B. vandii was conducted. These two species had similor bacteriological characteristics and were different from B. gladioli pv. gladioli, B. gladioli pv. alliicola and B. glumae. B. plantarii and B. vandii differed only in their utilization of L-rhamnose. B. vandii will be a consistent species with B. plantarii.

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To detect DNA polymorphism among isolates of the rice blast fungus Magnaporthe grisea, the AFLP (amplified fragment length polymorphism) technique was adopted. When each primer combination of EcoRl-AC/MseI-CA, EcoRI-AA/MseI-CA or EcoRI-AT/MseI-CA was used, every M. grisea isolate produced more than 30 fragments. The number was approximately 10 to 20 times higher than that for the RAPD technique using 10-nucleotide random primers. Moreover, in every primer set, 5 isolates from independent clonal lineages were distinguishable from each other by fragments showing polymorphism. On the other hand, 5 isolates including an original isolate and its pathogenic mutants produced the same number and size of amplified fragments in all 6 primer sets (the above plus EcoRI-AC/MseI-CC, EcoRI-AA/MseI-CC and EcoRI-AT/MseI-CC). These results show the higher utility and reproducibility of the AFLP technique in elucidating the ecology of rice blast fungus.

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The thermal death range of conidiospores of Mycoaellosiella nattrassii, the casual fungus of leaf mold, was examined under several conditions. Conidiospores in sterilized water perished within 5 days after treatment at 40°C, and conidiospores that formed on dry leaf lesions which showed inferior heat resistance showed a higher survival rate for more than 30 days after treatment at 40°C. Moreover, conidiospores on glass slids survived for 20 days at a hight rate of 37.1-10.9%.

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Mechanisms of varietal resistance to the whitebacked planthopper, Sogatella furcifera, in a Chinese japonica rice "Chengjiang 06 (CJ-06)" were investigated in comparison with a susceptible hybrid rice "Shanyou 63 (SY-63)". Field experiments revealed definite field resistance of CJ-06 to S. furcifera. The immigrants exhibited non-preference to CJ-06 and failed to establish progeny, whereas they preferred to settle and reproduced CT-06 well on SY-63. Under a free-choice condition, significantly fewer individuals alighted on CJ-06 than did on SY-63. Significantly less honeydew exeretion by S. furcifera females on CJ-06 than on SY-63 indicated suppressed sucking on CJ-06. Both fecundity and egg hatchability were greatly reduced on CJ-06 as compared with those on SY-63, when newly emerged females were fed on CJ-06. The fertility of S. furcifera on CJ-06 was only about one tenth of that on SY-63. S. furcifera eggs suffered high mortality in watery lesions at oviposition sites on CJ-06. The watery lesions rapidly led to the formation of conspicuous necrotic symptoms before the eggs hatched. The egg mortality in the watery lesions occurred within 1-2 days after oviposition. Such watery lesions seldom occurred in SY-63, where the egg mortality was very low. It is concluded that sucking suppression and ovicidal reaction are the critical components for the Sa furcifera resistance of CJ-06, which is expressed as not only antixenosis against S. furcifera immigrants, but also antibiosis to reduce fecundity and egg hatchability of inhabitants, respectively.

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