Grafting Presentation by Michael Crone Why grafting? • Ensuring to get a plant identical to the cultivar (superior to a seedling due to years of selection and breeding) Only partly true – Some important cultivars emerged as “chance seedlings” – Examples: avocado cultivar Hass, Granny Smith apple • Earlier flowering and fruiting as ‘juvenile phase’ is bypassed Careful: In some species such as Plinia cauliflora (Jaboticaba) the juvenile phase can’t be significantly shortened. • Dwarfing effect • Vigour effect (weak own roots, but vigorous on superior rootstock; eg Citrus inodora on Carizzo) • “To fill two needs with one deed” - combining best rootstock (e.g. disease resistance, salt tolerance, cold hardiness) with best fruiting wood (bred for good fruiting) Advantage over genetically identical cuttings/marcots (might not have best root systems eg lack of taproot, soil borne disease resistance) • Space saver / pollination – obtaining two or more cultivars / genetic stock on one tree • Time saver – get fruit from new cultivar in 2nd year by topworking advanced tree • Repair work (bridge graft) • Virus detection (when scion of unknown virus status is grafted on virus-susceptible rootstock) Priority One: Respect genetic limitations of grafting More useful to look at botanical names Example: and the taxonomy of plants Finding a rootstock for grafting pitomba-da-bahia • Pitanga • Pitangatuba ? • Sweet Cherry • Sour Cherry • Surinam Cherry • Brasil Cherry • Cherry de Rio Grande • ??????????? Kingdom: Plantae Problem with common names: Family: Myrtaceae • Instances where same name is applied to Genus: Eugenia several plant species Species: Eugenia luschnathiana • Often don’t reflect their relatedness with each other E. luschnathiana closest relative is Eugenia involucrata, so highest Genetics of rootstock - scion essential chance that both are graft-compatible Therefore: As grafters we trust in professional match-making! Get the closest match possible: Best: Rootstock and scion from the same species (Example: Scion of cultivar ‘Palmer’ mango on ‘Kensington Pride’ as rootstock) Potentially possible: Rootstock and scion are closely related species from the same genus (must prove to be compatible species) Avoid: Scion and rootstock from different genus (rare exceptions e.g. Pear on quince – both are from a different genus) Never: Scion and rootstock from different families However: In some cases ‘same species grafts’ are not possible due to some cultivars being graft incompatible (for example in lychees and apples! – Interstock that is compatible with both rootstock and scion might overcome this problem) Priority two: Select best possible plant material • Scions from well-managed fruit trees / choose healthy rootstocks • Scions being upright, sun- exposed (outside canopy) • Scions unblemished, free from obvious pests and diseases important Quality of rootstock and scion Genetics of rootstock - scion essential Priority three: Graft during the best time of year Easiest rule: When both rootstock and scion are actively growing (ideally just before bud burst of scion) • The earlier, the better to get the longest growth period for the new plant to grow before winter dormancy • With the defoliating and complete Favourable season sealing of scion grafting is also possible in mid-summer important Quality of rootstock and scion Genetics of rootstock - scion essential Still important: Aftercare Don’t you forget about me… Common mistakes: • Graft region gets sunburned (Pots to be moved around, field-grafts can be shielded with shade cloth) • Not removing rootstock shoots in time • Over- or underwatering (defoliated grafted plants require less water) Appropriate aftercare • Lack of fertiliser • (Field) grafting without checking weather forecast Favourable season important Frequent observation can correct: Quality of rootstock and scion • Mechanical damage • Fungal damage Genetics of rootstock - scion essential • Damage by pests Which method to choose • Approach graft being the safest technique, as scion still allowed to remain on donor plant until graft union is formed Same Scion smaller diameter diameter • or “off-centre” Cleft graft a good all-round method Central cut cut • Saddle graft with grafting tool guaranties precise match, however Grafting technique only allows for thick-diameter grafts of approx. 1cm diameter; certain wood more suitable than other (eg Appropriate aftercare apple) important • Sealing with stretchable wax-coated Favourable season tape maximises grafting season as it protects scions from drying out or exposure to moisture Quality of rootstock and scion Most important: Sharp grafting tools and matching of cambium layers of Genetics of rootstock - scion essential scion + rootstock! To boast, or not to boast? – Grafter’s skills only “of advantage” The more basic key points below determine the Skills of grafter !? of advantage grafter’s success Grafting technique Or Appropriate aftercare important Favourable season Your grafting skills may not overcome Quality of rootstock and scion sub-optimal circumstances Genetics of rootstock - scion essential So how many grafts have you done? – Let statistics work for you • Grow more than one No. of replications rootstock, so you can Skills of grafter of advantage graft several Grafting technique • If you have only one Appropriate aftercare rootstock, but several important branches, graft all Favourable season branches Quality of rootstock and scion Genetics of rootstock - scion essential The “joker” card to be extra sure or to increase chances in unfavourable • Removal of scion leaves 1- circumstances 4wks before cutting the scion tricks to increase • Water the donor tree very chances of success well 1-2 days before harvest • Harvest scions in the morning • Sterilise scions with alcohol swabs No. of replications of advantage • Immerse scions in fungicide Skills of grafter plus insecticide solution before wrapping up Grafting technique • If limited material, cut ordinary material to practice Appropriate aftercare and do important one when you feel at your best important • If unique chance comes Favourable season outside grafting season: break dormancy (glasshouse, Quality of rootstock and scion heatmat) or store wrapped scions as long as possible until spring comes essential Genetics of rootstock - scion • Distribute material to others Grafting success pyramid tricks to increase 100% success chances of success No. of replications Skills of grafter of advantage Grafting technique Appropriate aftercare important Favourable season Quality of rootstock and scion Genetics of rootstock - scion essential Success possible Grafters in the club – a quick search in Facebook: More than this list and constantly growing • Jack Teh • Amanda Sunley • Hau Ling • Mike Jones • Zechy Coyte-King • Simon Boyle • YenFye Yap • Guy Buters • John Stretch • Ray Sachse • Troy Bailey • Ro Richardson • Wayne Prangnell • Cherise Haslam • Barry Madsen • Rachel Solomon • Richard Pittaway • Adrian Azzari-Colley • James • Matt Checksfield • Jimmy Ho • Rachael Wedd • Derek Hodges So what are RFCWA members are up to in regard to grafting? James Multigrafting Example: 4 different mulberry cultivars on weeping rootstock Troy Bailey – Approach grafting P. lucuma Pouteria P. multiflora arguacoensium Pouteria used as rootstocks (excess arguacoensium Pouteria available) arguacoensium rare single branch plant to be propagated; scion too precious to be cut off Wayne Prangnell Grafted Annona neosalicifolia (rare) on Annona cherimola rootstock Richard Pittaway Root – shoot graft (Morus macroura, White shahtoot) Own interests Micrografting Interstock experiments (stem less than 3mm thick) • My theory that juvenile stock has best healing interstock capacity (apart from embryonic tissue) • Is done just above the first internode (only side shoots from 2 nodes need to be • To get additional dwarfing removed); less risk that rootstock overtakes • Potentially extra yield if right graft combination • Slow growing species that remain small can be • Overcoming graft incompatibilities grafted much earlier and are easier to match • Effects well documented for apple, with the small-diameter branches of the adult some work done on mango and plant (eg Eugenia involucrata) avocado Young graft succeeds • but too late in season Failures • and dies during winter despite success: Most common problems Failures despite success: Most common problems Graft is added on mature tree, but dies back the next year due to too many competing mature branches) Failures despite success: Most common problems Differences in vigour turn into problems some years later Failures despite success: Most common problems Underestimating influence of tree architecture acrotony Graft likely to be overgrown by rootstock suckers mesotony Eugenia brasiliensis (grumichama) basitony Underestimating influence of tree architecture: Acrotony of many avocado cultivars acrotony Manipulations to overcome acrotony Low vigour cultivar Early training of rootstock: change supported by acrotony versus acrotone branches into horizontal high vigour cultivar but branches that trigger upright shoots suppressed as a side branch suitable for multi grafts (Find slideshow of John Yoshimi Yonemoto 2016 in “Files” of our Facebook group about avocado pruning) Cultivar 2: high vigour Cultivar 1: low vigour Rootstock The neighbours’ cat summary • Graft, observe and protect your plants • Surround them with warmth and care Thank you for listening!.