| Phytophthora root rot, caused by Phytophthora cinnamomi Rands., is a severe disease on blueberry (Vaccinium corymbosum L.) in poorly drained soils. Blueberry growing areas in Arkansas have relatively shallow soil with compacted clay layers (Sterne, 1982), and thus, there is the possibility of spread of disease in the spring with high rainfall. Management practices therefore should be varied accordingly. These studies indicate that infection by Phytophthora could be severe with frequent application of water if there are periods of flooding. Thus, in the field, application of water should be reduced in these areas. However, if the field is not mulched, frequent application of water could be beneficial for increased growth. Data revealed higher disease incidence with weekly and biweekly flooding. However, mulching did not affect root infection.;The potential of biocontrol of blueberry (Vaccinium corymbosum L.) root rot caused by Phytophthora cinnamomi (Rands) and growth promotion was explored using bacteria and fungi. Blueberry plants of the cultivar 'Blucrop' were grown in pastebrized and in nonpasteurized soil infested with Phytophthora cinnamomi. Biocontrol candidates Gliocladium virens Gl 21 and Pseudomonas corrugata 114 significantly reduced colonization by P. cinnamomi in infested pasteurized soil. In non-pasteurized soil infested with P. cinnamomi, G. virens significantly reduced the disease and increased the plant growth compared to the control. Addition of Gliocladium virens to plants in the growth promoting study increased leaf area and the number of leaves produced in a four month growing period in pasteurized soil. The results suggest that G. virens and P. corrugata strain 114 may have potential as biocontrol agents for blueberry root rot, thus providing a potential alternative to current disease management practices in Arkansas. The study on growth promotion revealed the potential of G. virens as an inoculant of blueberry plants in the nursery or at transplanting for increased growth.;Pseudomonas corrugata strain 114 was shown to inhibit Phytophthora cinnamomi in vitro and in vivo. The antifungal compound isolated from the bacteria suppressed the growth of Phytophthora cinnamomi in-vitro. The compound had a molecular weight of 430. A study done on characterizing Phytophthora cinnamomi isolates from blueberry in Arkansas based on their nuclear DNA (nuDNA) restriction fragment length polymorphisms revealed that all the isolates from blueberry tested showed a similar RFLP pattern. |
