Alternaria Diseases of Cabbage and Related Plants

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: the same plaoe of inoculation were entirely browned. A fragment fron one diseased spot was examined under the microscope, and a large number of spores, many in chains of two, were observed. Eight days after inoculation a successful attempt was made, bythe spore dilution method, to isolate the organism....
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Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: the same plaoe of inoculation were entirely browned. A fragment fron one diseased spot was examined under the microscope, and a large number of spores, many in chains of two, were observed. Eight days after inoculation a successful attempt was made, bythe spore dilution method, to isolate the organism. Eleven days after inoculation the plant left uncovered, which up to this time showed no sign of infection, was placed under a bell Jar after large drops of water had been placed on the inoculated areas. The inside of the bell jar was sprayed with water. Three days later there appeared infection in three areas inoculated. Six days after being placed under the bell jar all four areas inoculated were infected, three areas showing diseased spots about one centimeter in diameter. Nine days after being placed under the bell jar one spot measured nearly two centimeters in diameter. This spot was characteristic of those usually produced by A. brassioae. It showed irregular concentric rings, was brownish at the center with abundant conidia, and had a light yellow margin at the border which shaded gradually into the surrounding tissue. The lower surface was darker in color than the upper. On the whole, the spot was not as dark as is usual on leaves in nature. The other spots were similar in appearance but smaller. The conidia were in chains on short oonidiophores which grew in groups from the leaf. Another experiment was undertaken in which cabbage plants about five inches high in pots were employed, and were treated as follows: A suspension of A. brassicae conidia in water was made from a strain secured from the University of Wisconsin plot. Abundant spores were aeeured by the use of the microscope. A very small drop was placed on a definite spot of the leaf and with a flamed ...