Evaluation of grafting for the mature green tomato production system Brenna Aegerter Scott Stoddard UCCE San Joaquin Co. UCCE Merced Co. University of California Cooperative Extension Minghua Zhang & Mike Grieneisen Department of Land, Air & Water Resources University of California, Davis California Department of Food & Agriculture Specialty Crop Block Grant 14027 California Department of Pesticide Regulation Pest Management Research Grant 16 PML R004
Why graft tomatoes? Increase in vigor, fruit size and yield Combine features of two varieties Scion: Desireable fruit traits Rootstock: Increased vigor Resistance and/or tolerance to soil-borne disease Increased stress tolerance Source: www.mightymato.com (Plug Connection)
www.vegetablegrafting.org
Field trial experimental plan Source of grafted plants: Growers Transplanting, Salinas Plot size: 40 feet, with a minimum of 20 plants per plot Bed configuration: 60 beds, 20 spacing in row Replicates: four, randomized complete block design Treatments (scion/rootstock combinations) Scions: Bobcat, HM1794, Dixie Red, Galilea (Roma) Rootstocks: Maxifort, DR0138TX, BS01543756 All combinations of the above, plus non-grafted controls
Sterile trays and sterile media hand seeded early March, five weeks before grafting date Grafting clips are added to rootstock Rootstock & scion plants cut at 45⁰ angle And scions are placed so that the two surfaces align. Grafting is most successful if the two plants are of similar diameter
Repeat 230 times per tray. and do 24 trays in all. Eight more trays held the non-grafted control plants. The grafted plants are held in a healing room at 95-100% humidity and 80⁰F for about a week.
MARKET YIELD (TONS/AC) 30 25 20 15 10 5 a 28.0 23.8 21.2 bc 17.5 ab 27.8 ab 26.5 22.1 23.8 24.6 25.0 24.3 19.2 21.4 17.7 c 16.0 bc 17.5 0 MAXIFORT DR0138TX BS01543756 NON-GRAFTED MAXIFORT DR0138TX BS01543756 NON-GRAFTED MAXIFORT DR0138TX BS01543756 NON-GRAFTED MAXIFORT DR0138TX BS01543756 NON-GRAFTED BOBCAT HM1794 DIXIE RED GALILEA
2016 trial, San Joaquin County ROOTSTOCK MEANS Total fruit yield v Market yield v Size distribution (% fruit by weight) x Maturity Vigor (T/A) difference (T/A) difference X-large Large Medium (% red) rating y NDVI z MAXIFORT 34.2 a (33%) 25.5 a (31%) 42 34 25 4 3.6 0.78 DR0138TX 30.7 a (19%) 23.3 ab 38 34 28 5 3.9 0.79 BS01543756 30.2 ab 20.9 b 31 33 37 8 1.8 0.72 NON-GRAFTED 25.7 b 19.5 b 29 35 36 7 1.9 0.73 Rootstock effect P value 0.0002 0.0008 (round types only) sig. interaction of scion & rootstock effects < 0.0001 CONTRAST: GRAFTED VS. 31.7 (23) 23.2 (19) 37 34 25 6 3.1 0.76 NON-GRAFTED 25.7 19.5 29 35 36 7 1.9 0.73 Contrast P value 0.0001 0.0029 Means in the same column followed by the same letter are not significantly different according to Tukey's HSD test. v Total fruit weight includes culls and undersize fruit, while marketable yield excludes these two categories w Percentage difference in yield of grafted plants compared to the non-grafted controls. x Size distribution of marketable fruit based on USDA sizing standards. Note that cv. Galilea is a Roma-type which follows different sizing standards than round types. y Vigor of the vines evaluated visually just before harvest and assigned a rating based on a scale from 1 to 5. 1 = vines small, fruit coverage poor, new growth little to none. 2 = vines medium sized, covering bed, fruit coverage weak, new growth little to some. 3 = vines medium to large, fruit coverage good, new growth good. 4 = vines large, fruit coverage excellent, new growth very good. 5 = Vines huge, fruit coverage excellent, new growth significant. z Normalized difference vegetation index (NDVI) measurements made with a handheld meter held over the bed (Trimble Greenseeker)
(ALL ON A PER ACRE BASIS) CONVENTIONAL GRAFTED DIFFERENCE plant spacing 20" spacing 24" spacing plants per acre 5,227 4,356 seed (conventional $0.022 each) $ 115???? transplant nursery (conventional $ 0.028 each) $ 146???? other cultural costs (excl. above & harvest) $ 1,180 $ 1,180 SAME YIELD ASSUMPTIONS (tons per acre) 16TONS 21.6TONS 35% HIGHER YIELD ASSUMPTIONS (25-lb boxes per acre) 1,280 BOXES 1,728 BOXES HARVEST costs (pick, haul, pack) $3.78 per box $ 4,838 $ 6,532 35% HIGHER GROSS REVENUE at $5 per box $ 6,400 $ 8,640 $ 2,240 at $6 per box $ 7,680 $10,368 $ 2,688 at $7 per box $ 8,960 $12,096 $ 3,136 GROSS REVENUE minus operating expenses (excl transplant costs) at $5 per box $ 382 $ 928 $ 547 at $6 per box $ 1,662 $ 2,656 $ 995 at $7 per box $ 2,942 $ 4,384 $ 1,443 At $7/box, 35% yield increase justifies an increase from $ 0.03 to $0.36 per transplant
Source: Djidonou, et al. (2013) Economic analysis of grafted tomato production in sandy soils of northern Florida. HortTechnology 23(5): 613-621.
Challenges Higher establishment costs, higher risk Plant availability, automation of grafting No rootstocks with resistance to Fusarium wilt race 3 or Verticillium wilt race 2 Location of graft union relative to soil surface Variability, rootstock x scion interactions
Thank you and any questions?