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Bacterial panicle blight (BPB), caused mainly by the bacterial pathogen Burkholderia glumae posed a higher level of threat to rice production worldwide in recent years. Here, we report the response of over 290 rice entries evaluated by artificially inoculating with a bacterial suspension under field conditions. From the Uniform Regional Rice Nursery (URRN) field screening, nearly 10 percent and 6 percent of the entries showed a resistant and moderately resistant reaction, respectively. A subset of 10 entries showed lower BPB disease in both the URRN and Arkansas Rice Performance Trials (ARPT). From 60 symptomatic samples screened on semi-selective medium, 52 were further evaluated by molecular test. Among these, 45 isolates were confirmed as B. glumae. The remaining seven were bacteria other than B. glumae and none of these seven isolates matched to B.gladioli. The three methods of inoculation (clip, direct injection and panicle) tested showed distinct disease phenotypes between cultivars that traditionally have been considered resistant or moderately resistant. Direct injection of bacterial inoculum into the sheath caused pathogen-related necrotic spots around the site of inoculation but not in sheaths injected with water alone. The genes Os1g32460, Os05g30500, Os11g31190, Os11g12340, Os11g12330, Os11g12040, Os11g12300, Os11g12000 and Os08g25050 were tested to determine if they are differentially expressed between the moderately resistant cultivar Jupiter and the susceptible cultivar Bengal after inoculation with B. glumae. While several of the genes were found to be upregulated after pathogen infection, none of the genes tested were differentially expressed between resistant and susceptible cultivars and the results were highly variable depending on the time of inoculation. Therefore, more optimization is needed. [ABSTRACT FROM AUTHOR]

Sheath blight disease of rice caused by Rhizoctonia solani AG1-1A is one of the major diseases of rice in Arkansas. Fungicides are often recommended if established threshold levels are reached and the disease progresses into the upper canopy during reproductive growth stages. The economic benefit of these applications must periodically be reevaluated based on changes in cultivars, management practices, and fungicide efficacy. The effect of fungicide application timing was evaluated on the cultivars LaKast and Jupiter at two seeding rates. Fungicide timings consisted of an untreated control and applications at panicle differentiation or boot split. All plots were artificially inoculated with the sheath blight fungus. Similar to 2016, both fungicide application timings resulted in reduced sheath blight incidence and higher grain yields compared to the untreated control. However, mean monetary gains were variable based on trial location and fungicide application timing. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide toxicity or autumn decline, also referred to as akiochi, shows black root rotting usually with stunted and yellowish rice foliage starting as early as two weeks following establishment of the permanent flood. In severe conditions, root crowns rot and are invaded by opportunistic fungi rendering dark brown discoloration. Rotting of root crowns specifically is referred to as autumn decline/akiochi and hinders the rice plant's ability with upward nutrient translocation from the roots. This paper reports on progress for two project objectives: 1) to search for practical methods to prevent or correct the root blackening and rotting associated with autumn decline; 2) to evaluate the degree of resistance or tolerance of common rice cultivars to autumn decline under greenhouse or field conditions. A field with a history of hydrogen sulfide toxicity and autumn decline was identified in Humphrey, Ark. for the purpose of conducting the following three tests. Two formulations of anoxygenic phototrophic bacteria products namely, spectrum PC and Spectrum PTB were tested in micro-plots (half barrels). At the same time, pot experiments were established to test cultivar tolerance differences and a greenhouse test was conducted to evaluate the effects of water temperatures, soil, and water sources on symptom development. The products PC and PTB were not effective in reducing the percent of root mass discoloration which was consistent with previous year's experiments. Spectrum PC did reduced root crown rot by 20% while Spectrum PTB lowered the damage by 40%. From the cultivar evaluation test, those that showed crown root rot above 3 on the 0-9 scale fell in the category of susceptible regardless of the intensity of root mass discoloration. Nearly 75% of the cultivars showed less than 35% root mass discoloration.Only 55% of the cultivars showed root crown damage that ranged from 5% to 30%. Root crown damage among the cultivars ranged from 0.5 to 9. The greenhouse test showed water temperature for flooding had much lower impact on hydrogen sulfide toxicity symptom or autumn decline than soil and water sources. Soil from a field with a history produced symptoms with either well water or chlorinated city water. However, the greenhouse soil with no history of toxicity or autumn decline showed no disease symptoms with the city water. Instead, it showed the autumn decline symptom with the well water. [ABSTRACT FROM AUTHOR]