Q.59 Which of the following statements are CORRECT for somatic cell hybridization?
P. For fusion of protoplast, dimethylsulfoxide (DMSO) is used as a fusogen
Q. The enzyme ‘Cellulase Onozuka’ used for protoplast isolation is sourced from Trichoderma
viride
R. The first report of somatic hybrid plants resulted from the fusion of protoplasts of Nicotiana
glauca and N. tabacum
S. Viability of isolated protoplasts can be determined by Evan’s blue staining
(A) P, Q (B) Q, S (C) R, S (D) Q, R
R and S are correct statements for somatic cell hybridization.
Question Breakdown
This GATE Life Sciences question tests protoplast technology fundamentals in plant biotechnology. Somatic hybridization fuses protoplasts (wall-less cells) to create hybrids overcoming sexual incompatibility, involving isolation, fusion, selection, and regeneration.
Statement Analysis
P: DMSO used as fusogen for protoplast fusion
False. Polyethylene glycol (PEG) and calcium ions are standard fusogens; DMSO is a solvent occasionally used but not primary fusogen.
Q: Cellulase Onozuka from Trichoderma viride
False. Onozuka R-10 cellulase is from Trichoderma viride, but typically paired with Macerozyme (Rhizopus) or Driselase (Basidiomycete); source attribution imprecise.
R: First somatic hybrid from Nicotiana glauca + N. tabacum protoplasts
True. Carlson et al. (1972) reported first interspecific amphidiploid hybrid via protoplast fusion, landmark in somatic hybridization.
S: Evan’s blue staining determines protoplast viability
True. Live protoplasts exclude Evan’s blue (plasma membrane intact); dead ones stain blue, standard viability assay alongside FDA.
Correct Choice
(C) R, S
Somatic cell hybridization correct statements cover protoplast fusion milestones and viability assays essential for GATE Life Sciences biotechnology prep.
Protoplast Technology Key Steps
-
Isolation: Cellulase + pectinase digest walls
-
Fusion: PEG/Ca²⁺ induce agglutination → membrane fusion
-
Selection: Fluorescence-activated sorting or iodoacetate inactivation
-
Regeneration: Callus → shoots → plants
Truth Table
| Statement | Content | Correct? | Reason |
|---|---|---|---|
| P | DMSO fusogen | No | PEG standard |
| Q | Cellulase Onozuka from T. viride | No | Source imprecise |
| R | Nicotiana glauca+tabacum first hybrid | Yes | Carlson 1972 |
| S | Evan’s blue viability | Yes | Standard assay |
GATE Exam Relevance
XL-Plant Biotech PYQ tests protocol specifics. Memorize: Nicotiana glauca/tabacum (first hybrid), PEG fusion, Evan’s blue/FDA viability, Onozuka cellulase. Cybrids (pomato) follow similar tech.
