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Title: Guava SSR analysis: Diversity assessment in US and similarity to accessions associated with reducing citrus huanglongbing in Vietnam

Author
item STOVER, EDDIE
item ARADHYA, MALLIKARJUNA
item GOZLECKI, S - AMRITA UNIVERSITY
item CRANE, J - UNIVERSITY OF FLORIDA
item Matsumoto Brower, Tracie
item Mayo Riley, Carol
item ZEE, FRANCIS
item GOTTWALD, TIMOTHY
item HALL, DAVID

Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2018
Publication Date: 10/1/2018
Citation: Stover, E., Aradhya, M., Gozlecki, S., Crane, J., Matsumoto Brower, T., Mayo- Riley, C., Zee, F., Gottwald, T., Hall, D. 2018. Guava SSR analysis: diversity assessment in US and similarity to accessions associated with reducing citrus huanglongbing in Vietnam. Journal of American Pomological Society. 72:242-250.

Interpretive Summary: The guava is native to tropical America but has been distributed across all tropical regions where selections have been made. Recent introduction of the citrus greening disease into Florida has compelled renewed interest in guava, since closely interplanting citrus and guava in Vietnam were reported to greatly slow disease progression. It was hypothesized that volatile chemicals (such as odors) released by guava may repel the Asian citrus psyllid which spreads the citrus greening bacterium. In this study, DNA analysis was conducted on all readily accessible U.S. guava types, as well as material from three Vietnamese citrus/guava orchards. The analysis indicated five distinct groups, and the Vietnamese guavas were placed in two of the five groups. Several guava varieties in Florida are in the same clusters as the Vietnamese cultivars. However, the sweet pink-fleshed varieties that have predominated in the western hemisphere did not cluster with the accessions from Vietnam.

Technical Abstract: The guava (Psidium guajava) is an evergreen tree in the Myrtaceae, which is native to tropical America. Recent introduction of huanglongbing (HLB, also known as citrus greening) into Florida has compelled renewed interest in guava, since closely interplanting citrus and guava in Vietnam were reported to greatly slow progression of HLB. It was hypothesized that volatiles in the guava may repel the Asian citrus psyllid (Diaphorina citri) which vectors the HLB causal bacterial agent. In this study, simple sequence repeat (SSR) analysis was conducted on all readily accessible U.S. guava accessions, as well as material from three Vietnamese citrus/guava orchards. Accessions included 73 distinct sources, and multiple samples were collected from 9 of these as an internal check. Ten SSR primer pairs were used in the analysis. Alleles per locus ranged from 4 to 8, with an average of 6.2. Forty different genotypes were identified, as several accessions appeared to be synonymous based on this analysis. The cluster analysis using the neighbor-joining method revealed four distinct affinities. The genetic differentiation within and among the four groups showed marked differentiation (FST = 0.325) and inbreeding was slight (FIS = 0.154). The Vietnamese accessions were placed in two of the five major clusters. Several guava varieties in Florida are in the same clusters as the Vietnamese cultivars. However, the sweet pink-fleshed varieties that have predominated in the western hemisphere did not cluster with the accessions from Vietnam.