Yuji Hosobochi Renato Braga Bryan Zingel

Challenges Breeding Commercial Rootstock

November 8, 2012 Maitland, Florida

1. Tomato a) Reasons for increased use of rootstocks b) Key rootstock traits c) Soil disease challenges d) Disease resistance breeding e) Comment

2. Pepper a) Reasons for use of rootstocks b) Advantages of rootstock c) Pepper grafting techniques d) Some results e) Comment

Presentation Overview Challenges Breeding Commercial Rootstock

Why is grafting increasing? • Numerous kinds of soil diseases break out because

of over crop. • High yield is demanded to reduce production costs. • Environment-friendly production.

Challenges Breeding Commercial Rootstock

Key rootstock traits? • Multiple disease resistance • Good germination and uniformity • Easy grafting • High vigor (interspecific > intraspecific)

Challenges Breeding Commercial Rootstock

PresenterPresentation NotesCommonly, Asian use intraspecific rootstocks. Because they set quality (taste) above quantity (yield). The taste of tomato grafted on interspecific rootstock is lower than the taste of tomato grafted on intraspecific rootstock.

Soil diseases on Tomato

Root knot nematode Meloidogyne incognita Meloidogyne javanica Meloidogyne arenaria Meloidegyne mayaguensis

Corky root Pyrenochaeta lycopersici

Challenges Breeding Commercial Rootstock

PresenterPresentation NotesRoot knot is caused by Meloidgyne sp. Resistant gene Mi-1 is very popular to control nematodes. This gene works well to M. incognita, javanica and arenaria but doesn’t work over 28C. Currently other race of incognita and species (mayaguensis) which break Mi-1 are increasing worldwide. Some solanum species are reported they have resistant genes against new nematodes, however, they are not practically used yet.

Corky root is caused by Pyrenochaeta lycopersici. This disease is severe in North America, Europe and Japan. There are 2 kinds of patho-type. (Japanese pathologists reported it in Japan) Type 1 grows under low temperature and has aggressive pathogenicity. Type 2 grows at higher temperature than type 1 and the pathogenicity is mild. Solanum habrochaites is high resistant to them. Habrochaites are used as interspecific hybrids.

Soil diseases on Tomato

Fusarium wilt Fusarium oxysporum f. sp. lycopersici race 1, race 2 and race 3

Bacterial wilt Ralstonia solanacearum Left: no grafted tomato Right: grafted tomato

Challenges Breeding Commercial Rootstock

PresenterPresentation NotesFusarium wilt is caused by Fusarium oxysporum f. sp. lycopersici. There are 3 kinds of races. Race 3 is severe in Mexico, Australia and Japan. The resistant genes were already found and work well. I2 gene is high resistant to race 1 and 2. I3 gene is high resistant to race 3. Bacterial wilt is caused by Ralstonia solanacearum. This disease is very severe in warm areas and hot season. The resistance was found from Solanum pimpineliforuim, but this resistance is poly genetic. It’s not easy to control bacterial wilt by only grafting.

Disease resistant breeding

• Use of MAS (Molecular Assistance for Screening)

• Inoculation test

Challenges Breeding Commercial Rootstock

PresenterPresentation NotesWe use molecular markers to screen disease resistance. Many kinds of molecular markers link to disease resistant gene are developed. MAS is very useful item. We can distinguish homogeneous resistance and heterogeneous resistance from susceptible ones. MAS helps speedy breeding.However MAS is not complete. We have to confirm the resistance by bioassays. After MAS, we confirm the resistance of progenies by inoculation tests.Sakata use molecular markers for Mi, I2, I3, Ve, pyl and Tm2a.

Comment 1. Disease resistance. Multi resistance required e.g..,

Mi / Mj / Ma / Fol: 1,2,3 / Vd-1 / Forl / Pl / ToMV. It takes long time to fix all of them. In case of resistance to Rs, the resistance is polygenic. More challenging to fix.

2. Scion compatibility. Strong vigor scions generally need medium vigor rootstocks and vice versa. The balance between quantity (yield) and quality (taste) is important. We have to supply a rootstock variety suitable for scion.

3. High germination / uniformity. Interspecific hybrids inclined to low germination. Sometimes priming is required.

4. Customer needs. Disease pressure, long cycle, GSPP, …

Challenges Breeding Commercial Rootstock

Why is grafting increasing? • Resistance to soil pathogens • Yield increase of >30% • Reduce the soil salinization • Increase the production longevity

Challenges Breeding Commercial Rootstock

Why is grafting increasing? • Faster solution ~ less time required • Less expensive than chemical treatment and

hydroponic cultivation • Health / food safety considerations • Environmental considerations • Organic production • Reduced chemical inputs / availability

Challenges Breeding Commercial Rootstock

Various grafting techniques

Challenges Breeding Commercial Rootstock

V “Splice” “Tongue”

Results:

Pepper roots with nematode Same pepper variety grafted. Without nematode Other disease resistances that

rootstock prevents: Phytophthora, Bacterial wilt, …

Challenges Breeding Commercial Rootstock

Results:

Increased yield potential Brazil - Green house in pepper production

Production of 24kg by plant in 15 months of harvest

Challenges Breeding Commercial Rootstock

Bacterial wilt control

Comment 1. Rootstock with new resistances, e.g., to Nacobbus

aberrans, Meloidogyne enterolobii, … 2. More tolerant to high EC (electric conductivity) and

water stress conditions 3. Improved tolerance to temperature stress,

nutriment utilization, … 4. Create a rootstock that increases the yield. The

actual rootstock can increase the yield in >30%. 5. Create a rootstock to the improve fruit quality, e.g.,

fruit with better color or sugar, …

Challenges Breeding Commercial Rootstock

Summary Comment 1. Unique local challenges. Modify and adapt

programs to target and address the local needs. 2. Cost / Risk of development. Challenge to address

new and developing markets. 3. Technical development and support. Challenge to

ensure this is adequate to provide the best opportunity for success.

4. Focus. Much of the high end commercial rootstock development and pioneering is orientated around high tech culture.

Challenges Breeding Commercial Rootstock

Slide Number 1Presentation OverviewWhy is grafting increasing?Key rootstock traits?Soil diseases on TomatoSoil diseases on TomatoDisease resistant breedingCommentWhy is grafting increasing?Why is grafting increasing?Various grafting techniquesSlide Number 12Slide Number 13CommentSummary Comment