Effect of Grafting on Roma-type Tomato Production in Southwest Florida

Roma-type tomato varieties with acceptable horticultural characteristics for Florida growers often do not have resistance to Fusarium crown rot (FCR), a soil disease affecting Southwestern Florida. Grafting can protect plants against FCR, but the extra cost of grafted plants is perceived as an obstacle for adoption of this technique by growers. Therefore, the objective of the study was to evaluate the performance of grafted vs. non-grafted roma-type tomatoes in plant growth, yield, and postharvest quality. Scions ‘Sunoma’ and ‘Mariana’ were grafted on rootstock ‘Maxifort’ (‘Maxifort’/‘Sunoma’ and ‘Maxifort’/‘Mariana’) and compared to non-grafted ‘Sunoma’ and ‘Mariana’ in a randomized complete-block design with four replications. The trial was planted on 25 Sept. 2012, with 22 in. between plants and 6 ft. between bed centers in Immokalee, FL. Plant growth data were collected at third harvest or 120 days after transplanting. Tomato fruit were harvested three times at the mature-green stage and graded into marketable size categories and unmarketable yield. A subsample of 20 breaker-stage fruit/plot was collected at first harvest and ripened to table ripeness. Postharvest evaluation included firmness, skin color, total soluble solids (TSS), and pH. Plant growth, yield and postharvest data were analyzed by analysis of variance (ANOVA) and mean separation by Duncan’s multiple range tests. Although there was a history of the Fusarium oxysporum f.sp. radicis-lycopersici in the field, there was low FCR incidence in the trial (< 3%). Of the grafted tomato plants, 21% produced rootstock suckers, which were removed during the production season. There were no differences in total plant biomass; however, grafted plants were taller than non-grafted plants. The highest, large-size tomato yield was produced by non-grafted plants at first harvest. ‘Sunoma’ produced the greatest total marketable, first harvest yields, but was not different from Mariana and ‘Maxifort’/‘Sunoma’. There were no differences among the treatments for total season, large-size tomato yield, whereas ‘Sunoma’ and ‘Maxifort’/‘Sunoma’ produced the highest total marketable fruit yields (all sizes and harvests combined) of 2,745 and 2,607 boxes/acres, respectively. ‘Maxifort’/‘Mariana’ had the firmest fruit, while ‘Sunoma’ and ‘Maxifort’/‘Sunoma’ produced the softest fruit. The best color was from ‘Mariana’ and the grafted treatments. The lowest TSS was found in ‘Maxifort’/‘Mariana’ and there were no differences in pH among fruit from grafted and non-grafted plants. With no FCR pressure there were no clear advantages to using grafted plants in roma-type tomato production, although rootstock suckering might have affected fruit yields in this study.