Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 16, 1999
Publication Date: N/A
Technical Abstract: Several Trichoderma virens (Gliocladium virens) strains have good biocontrol activity against Rhizoctonia solani on cotton seedlings. However, these strains lack several characteristics required to be commercially viable. For example, most cannot survive an entire season on the roots of a cotton plant in Texas. Also, the ability to control diseases early in the season is reduced by cool weather. Diseases such as damping-off by Pythium species and Thielaviopsis root rot are of particular interest. Other species of Trichoderma have tolerance to higher and lower temperatures than T. virens, but are not as effective as biocontrol agents on cotton. Protoplast fusion is a method that has been used in Trichoderma to successfully incorporate desirable characteristics and improve biological control efficacy. We used three effective biological control strains of T. virens in protoplast fusions with two cold tolerant strains of T. harzianum and a heat tolerant strain of T. pseudokoningii in an effort to develop improved biological control strains. Fourteen isolates that were stable through multiple transfers were obtained. One isolate was obtained that sectored into two distinct types after several transfers. Of eight fusants between T. virens and T. pseudokoningii, seven were morphologically T. virens and one was T. pseudokoningii. The T. pseudokoningii fusant had greater biological control activity against Rhizoctonia solani on cotton than the T. pseudokoningii parent and grew equally well at 40 degrees C. All of the T. virens fusants grew significantly faster than the T. virens parent at 40 degrees C. One of the seven T. virens fusants was significantly reduced in biological control activity compared to the T. virens parent.