Evaluation of the fungal endophyte Clonostachys rosea as an inoculant to enhance growth, fitness and productivity of crop plants

Clonostachys rosea strain 88-710 was evaluated for ability to promote growth and productivity of miniature roses, geraniums, and cucumbers grown in the absence or near absence of pathogens. For comparison, Pseudomonas chlororaphis strain 63-28 also was evaluated in cucumbers. For treatment of roses, conidial suspensions (5 x 10(6) conidia . ml(-1) water) of C rosea were applied at the cuttings stage, or after the first or second trimming of the foliage, or in combinations of these. Compared to the controls, the endophyte accelerated rooting of the cuttings, reduced root dieback following foliar trimming by over 70%, maintained rapid shoot growth, and reduced numbers of senescent and dead leaves by 55 to 80%. Flowers of treated plants developed earlier and more abundantly than in the controls, and the plants were shipping-ready 7 to 14 days earlier. Treatment of geranium cuttings by immersion in 5 x 10(6) conidia-ml(-1) increased root production three-fold and plant survival by 27%. In hydroponic cucumbers in a research greenhouse, application of C rosea to the nutrient solution at a final density of I x 10(5) conidia ml(-1) increased leaf area by 28% after 16 days, and root dry mass by 40% at 19 days. Corresponding values for Ps. chlororaphis applied at 1 x 10(5) CFU.ml(-1) were 39% and 48%. Neither organism influenced net CO2 assimilation rate or chlorophyll fluorescence per unit leaf area. In a related experiment C. rosea and Ps. chlororaphis, respectively, increased plant height by 48 to 66% and 60 to 71%, and root dry mass by 27 to 30% and 28 to 36%. In a commercial greenhouse, the respective microbes increased numbers of marketable cucumber fruit by 11.1 and 10.5%. We conclude that C. rosea strain 88-710 and Ps. chlororaphis 63-28 have potential for use as inoculants to enhance crop performance.