Question

Citrus rootstock which is tolerant to gummosis, root rot, tristeza and drought

• A. Karna khatta
• B. Cleopatra mandarin
• C. Sweet orange
• D. Carizzo citrange

Hint:

Choosing citrus rootstocks involves matching their tolerance profile to local challenges.
Cleopatra mandarin: Good all-around tolerance to gummosis, root rot, tristeza, and drought.
Carrizo citrange: Good for Phytophthora, tristeza, nematodes; moderate drought tolerance.
Sweet orange & Karna khatta: More susceptible to some of these issues.

Answer 1

The Correct Option is B

Citrus rootstocks are chosen for their ability to influence tree size, fruit quality, yield, and tolerance to various diseases and adverse soil/environmental conditions. We are looking for a rootstock tolerant to gummosis (caused by Phytophthora spp.), root rot (also often Phytophthora), Citrus Tristeza Virus (CTV), and drought.
(1) Karna khatta (Citrus karna): Tolerant to some conditions but can be susceptible to tristeza and gummosis depending on the strain/environment.
(2) Cleopatra mandarin (Citrus reshni): Known for its good tolerance to gummosis, root rot, Citrus Tristeza Virus, and also has good drought tolerance. It is also tolerant to citrus nematodes and has good compatibility with many scion varieties. This makes it a widely used and adaptable rootstock.
(3) Sweet orange (Citrus sinensis): As a rootstock, sweet orange seedlings are generally susceptible to Phytophthora (gummosis, root rot) and tristeza. Not a good choice for these tolerances.
(4) Carrizo citrange (Poncirus trifoliata \( \times \) Citrus sinensis): Citranges like Carrizo are known for tolerance to Phytophthora diseases, tristeza (depending on the specific CTV strains), and citrus nematode. They have moderate drought tolerance. Comparing the options, Cleopatra mandarin is often cited for its broad spectrum of tolerances including gummosis, root rot, tristeza, and notable drought tolerance, making it a strong candidate. While Carrizo citrange also has many of these tolerances, Cleopatra mandarin is particularly well-regarded for this combination. Cleopatra mandarin