关键词: 大麦, 青稞, 禾生指葡孢霉, 穗腐病, SRAP, 遗传多样性, 指纹检索表

Abstract:

【Background】In the high-latitude agricultural areas of Qinghai-Tibet Plateau and its peripheral regions, hulless or naked barley (Hordeum vulgare var. nudum) is the only small grain cereal crop in the local area, and it is also the major forage. Dactylobotrys spike blight, caused by Dactylobotrys graminicola, is a new fungal disease only found in the hulless barley growing areas in Qinghai-Tibet Plateau in recent years, which can attack several triticeae crops and cereal grasses and make a great challenge to security of hulless barley production.【Objective】The objective of this study is to research the genetic diversity, systemic evolution of the fungal pathogen of D. graminicola and its effects on the host seed germination, reveal the pathogen epidemics and spread ways, host-pathogen interrelationship and the primary inoculum, and to provide valuable information for disease control.【Method】The diseased plant samples were collected from the disease epidemic areas, and 27 strains were isolated from the typical infected host spike tissues. After identification based on its biological traits of anamorph, the single-conidium strains were cultivated and used for genomic DNA extraction. The whole genomic diversity was evaluated with SRAP markers and strain-specific markers were developed. The evolution relationship between D. graminicola and its related genera or species was analyzed using the two conserved loci of LSU and Rpb2. The conidium suspension was co-cultivated with the germinated or ungerminated hulless barely seeds, and its effect on barley seed germination and seedling growth of hulless barely was analyzed.【Result】Fourteen SRAP primer combinations were selected to detect genetic diversity of D. graminicola strains, and on average, 90 polymorphic DNA bands were produced per primer combination. For D. graminicola strains, only 1.4 strain-specific markers were developed averagely. The strain of Z 13008 derived from common wheat possessed the most 7 SRAP markers. For Fusarium graminearum used as a control strain, 20 specific markers were identified. It was confirmed that there is no close relationship between strain origins of D. graminicola and their genetic diversity. Among the identified strains, only those like Z 13008 from common wheat, Z 13024 from rye and another two (Z 13013 and Z 13006) from hulless barley showed higher differences in genetic diversity compared with the others, indicating that the genetic variation level of D. graminicola population is low. Besides, it is feasible to characterize the 21 D. graminicola strains with a DNA dichotomous fingerprinting key constructed with 20 SRAP markers. D. graminicola is genetically closely related to the fungal species of genus Nectria through phylogenetic analysis. When inoculating seeds with conidial suspensions before germination, the pathogen had no significant suppression on seed germination and growth of seedlings and their roots. While it could infect and restrain seedling root growth when co-cultivating the germinated seeds with conidial suspensions, and resulted in the infected young roots changing into light brown color, but had no significant effect on seeding growth.【Conclusion】D. graminicola showed lower genetic diversity compared with its relative species of F. graminearum, and its genetic variation is closely related to its host plant species. The pathogenicity of the pathogen is weak, and it has no obvious inhibiting effect on the germination and seedling growth of hulless barley.

Key words: Hordeum vulgare, Hordeum vulgare var. nudum, Dactylobotrys graminicola, Dactylobotrys spike blight, SRAP, genetic diversity, fingerprinting key