Monitoring bacterial panicle blight disease of rice and germplasm evaluation for resistance in Arkansas in 2015

Authors: WAMISHE, YESHI - University Of Arkansas; MULAW, TEMU - University Of Arkansas; Jia, Yulin; GEBREMARIAM, TIBEBU - University Of Arkansas; BELMAR, SCOTT - University Of Arkansas; KELSEY, CHRISTY - University Of Arkansas

Submitted to: B. R. Wells Rice Research Studies
Publication Type: Other
Publication Acceptance Date: 6/4/2016
Publication Date: 8/4/2016
Citation: Wamishe, Y., Mulaw, T., Jia, Y., Gebremariam, T.A., Belmar, S.B., Kelsey, C.D. 2016. Monitoring bacterial panicle blight disease of rice and germplasm evaluation for resistance in Arkansas in 2015. B. R. Wells Rice Research Studies. Vol 634, pp120-125.

Interpretive Summary: Rice bacterial panicle blight (BPB) is one of the major biotic factors that can cause severe yield loss in Southern rice states of the U.S.A and several other rice growing countries. To date, despite hybrid rice and Jupiter having shown moderate resistance under field conditions, no complete genetic resistance to BPB has been identified from cultivated rice. In 2015, a total of 165 panicle samples from across Arkansas were collected and analyzed. A total of 72 samples tested positive for Burkholderia glumae based on growth in culture. However, using genetic markers only 45 were confirmed as the B. glumae organism. When tested with genetic markers for a related bacterium, B. gladioli, none tested positive indicating B. glumae is the major causal agent of BPB symptoms in these samples. In addition, in 2015 some 290 new breeding lines, were evaluated for BPB resistance using artificial inoculation with the bacterium. Only about 20% of the breeding lines appeared to be resistant or moderately resistant while the rest were varying degrees of susceptibility. Rice varieties that were late maturing appeared to be resistant but this may be due to that they escaped infection as a result of unfavorable weather conditions during and after inoculation in the latter part of the season.

Technical Abstract: Rice is a major cereal crop that contributes significantly to the global food security. Rice production is challenged by both abiotic and biotic stresses. Rice bacterial panicle blight (BPB) has been recognized as one of the major biotic factors that can cause severe yield loss in Southern rice states of the U.S.A and several other rice growing countries. Cultural practices such as early planting with adequate seeding and nitrogen fertilizer rates have experimentally shown to reduce the disease incidence. To date, chemical options are not available for use in the U.S.A. None of the current conventional commercial rice cultivars appear to have complete resistance to BPB. Hybrid rice and Jupiter have shown moderate resistance under field conditions. Breeding for disease resistance requires continuous efforts of enriching gene pools to have a source of resistance genes to work with and tackle the yield robbing problems. In the past few years, research efforts have been focused toward understanding the causal agent and evaluating rice for resistance to BPB. In 2015, a total of 165 panicle samples were collected from nine rice producing counties and were represented by either fully or partially blank kernels with or without floret discoloration. Samples were collected largely from various experimental field trials conducted across Arkansas. Of 165 field samples collected, 72 samples were considered positive for Burkholderia glumae based on bacterial growth on culture medium. However, using a genetic marker approach with specific primers, only 45 were confirmed as positive for B. glumae. When tested with a B. gladioli primer, none tested positive indicating B. glumae as the major causal agent of BPB. Two rice germplasm nurseries, namely ARPT and URRN consisting of 90 and 200 entries, respectively, were evaluated for BPB using artificial inoculation at an experimental field in 2015. A 0 to 9 disease rating scale was used where 0 is no disease and 9 severe disease with blank panicles. Based on the reference reactions of Jupiter (Moderately Resistant) and Bengal (Susceptible), 27 entries were categorized as Resistant, 34 Moderately Resistant, 36 Moderately Susceptible, 126 Susceptible, and 62 Very Susceptible. Late maturing rice entries appeared relatively clean and were placed in the resistant category. However, further investigation is required to ensure true resistance to BPB in late maturing rice. A false resistance response or “escape” maybe due more to unfavorable weather conditions that existed during and after inoculation in the latter part of the season.