1967年,日本土居养二等在感染萎缩病的桑树、患丛枝病的泡桐树和马铃薯,以及感染翠菊黄化病的矮牵牛的韧皮部筛管细胞中发现了一类新的微生物——类菌原体。这一新病原引起了科学家的重视,并进行了大量研究,从而导致了另一类植物新病原——类立克次氏体的发现。多年来,人们一直认为三叶草棒叶病系由病毒所致。1972年,Windsor和Black在感染棒叶病的三叶草和长春花韧皮部中观察到一类在健株中存在的微生物。它的一些特性与引起动物和人体疾病的立克次氏体类 In 1967, a new type of microorganism was found in phloem cells of mulberry trees infected with atrophy, paulownia trees and potatoes suffering from birch disease, and phloem sieve cells of petunia infected with aster yellow disease. - Mycoplasma. The new pathogen has drawn the attention of scientists and extensive research has led to the discovery of a new class of plant pathogens, rickettsia. For many years, clover leaf-stick disease has always been thought to be caused by a virus. In 1972, Windsor and Black observed a class of microbes present in healthy plants in leaf clover-infected clover and vinca limbs. Some of its features are associated with rickettsias that cause disease in animals and humans