Question:
Citrus rootstock which is tolerant to gummosis, root rot, tristeza and drought
Citrus rootstock which is tolerant to gummosis, root rot, tristeza and drought
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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.
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.
Updated On: Jul 2, 2026
- Karna khatta
- Cleopatra mandarin
- Sweet orange
- Carizzo citrange
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The Correct Option is B
Approach Solution - 1
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
(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
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Approach Solution -2
Elimination approach:
Sweet orange seedlings are widely known to be susceptible, not tolerant, to Phytophthora-caused gummosis and root rot, which rules out that option immediately. Karna khatta offers useful vigour and some salinity tolerance but is not particularly noted for combined tristeza and gummosis tolerance, weakening that option too. That leaves Cleopatra mandarin and Carrizo citrange, both genuinely resistant to Phytophthora and citrus tristeza virus. The deciding factor is drought tolerance: Cleopatra mandarin is specifically valued in rootstock trials for performing well under moisture-stressed, drier conditions, whereas Carrizo citrange prefers more consistently irrigated soils and shows only moderate drought tolerance. This combination of traits singles out Cleopatra mandarin as the best fit for all four requirements.
Sweet orange seedlings are widely known to be susceptible, not tolerant, to Phytophthora-caused gummosis and root rot, which rules out that option immediately. Karna khatta offers useful vigour and some salinity tolerance but is not particularly noted for combined tristeza and gummosis tolerance, weakening that option too. That leaves Cleopatra mandarin and Carrizo citrange, both genuinely resistant to Phytophthora and citrus tristeza virus. The deciding factor is drought tolerance: Cleopatra mandarin is specifically valued in rootstock trials for performing well under moisture-stressed, drier conditions, whereas Carrizo citrange prefers more consistently irrigated soils and shows only moderate drought tolerance. This combination of traits singles out Cleopatra mandarin as the best fit for all four requirements.
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