The infection process of bacterial blight of anthurium was monitored with a bioluminescent strain of Xanthomonas campestris pv. dieffenbachiae. The relationship between symptom expression on infected leaves (assessed visually) and the extent of bacterial movement within tissues (evaluated by bioluminescence emission) varied among anthurium cultivars. In several cultivars previously considered susceptible on the basis of symptom development alone, bacterial invasion of leaves extended far beyond the visually affected areas. In other cultivars previously considered resistant, bacterial invasion was restricted to areas with visible symptoms. In three cultivars previously considered resistant, leaves were extensively invaded by the bacterium, and yet few or no symptoms were seen on infected leaves. The pathogen was consistently recovered from leaf sections emitting bioluminescence but not from sections emitting no light. At an early stage of infection, no significant differences in the percentages of infected areas as determined by visual assessment were observed in any of the cultivars. However, differences among cultivars were detected by bioluminescence as the disease progressed, because bacterial invasion was not always accompanied by symptom expression. In susceptible cultivars, the advancing border of infection was 5 to 10 cm inward from the margins of the visible symptoms and often reached to the leaf petiole even when symptoms were visible in <10% of the total leaf area. Comparisons of anthurium cultivars in which a nondestructive method was used to quantify the severity of leaf infection by a bioluminescent pathogen have enabled us to evaluate susceptibility and resistance to bacterial blight accurately. Such evaluations will be of importance in breeding resistant cultivars for disease control.

emerging leptons produced via a n exchange of a ACKNOWLEDGMENT single photon (based on the parton model) is given in the l a s t paper [Eq. (35)] of Ref. 7 and may b e of I a m sincerely grateful to Professor Norman s o m e use. Christ f o r his sponsorship of this problem. *This research was supported by the U. S. Atomic Energy Commission. IF. Ehlotzky and H. Mitter, Nuovo Cimento g, 181 (1968), and references therein. his is to acknowledge the help of Professor L. M. Lederman in carrying out a similar calculation on radiative corrections to the decay of an indefinitemetric photon (unpublished). 3~. Christenson et a l . , Phys. Rev. Lett. 25, 1523 (1970). 4~h a t is, E = E , +. . . contributions from higher-order radiative corrections to the lepton-pair production cross section. 5~. D. Bjorken and E. A. Paschos, Phys. Rev. 2, 1975 (1969). %. D. Drell and T.-M. Yan, Phys. Rev. Lett. 25, 316 (1970). 7~. Fujikawa, Nuovo Cimento E, 83 (1972), E, 117 (1972) ; V. M. Budnev et a1 . , Phys. Lett. x, 526 (1972); A. Soni, Phys. Rev. D 8, 880 (1973). 8~2 u is computed in the last paper of Ref. 7.We attempt to modify the Kuti-Weisskopf quark-parton model s o as to obtain agreement with recent experimental and theoretical results. We find that, at the cost of sacrificing some simplicity, reasonable phenomenological fits can be obtained.

No abstract

No abstract

We attempt to show that the interpretation of the Y 8 (1405) resonance a s a bound state of quarks i s not ruled out by the data presently available. Our results, however, also indicate that such an interpretation does not answer some of the objections that have been raised to the more conventional picture of this resonance a s EN bound state.