Infestation by diseases, insects, and nematodes
Explanation
In plant breeding and biotechnology, factors limiting crop productivity are classified into two primary categories: Biotic and Abiotic stresses. Developing varieties resistant to these stresses is a key objective of both conventional breeding and genetic engineering (e.g., developing transgenic organisms like Bt crops).
Detailed Analysis:
- Biotic Stress: This refers to stress caused by living organisms. It includes damage inflicted by pathogens (bacteria, fungi, viruses), insect pests, nematodes, and competition from weeds. Therefore, Biotic Resistance is the inherent or engineered ability of a plant to withstand or repel these biological threats.
- Abiotic Stress: This refers to stress caused by non-living environmental factors. Examples include temperature extremes (heat, frost), water conditions (drought, water-logging), soil salinity, and nutrient deficiencies.
Option-wise Analysis:
- Environmental stresses like drought and heat is incorrect: Drought and heat are physical environmental factors, classified as abiotic stresses.
- Infestation by diseases, insects, and nematodes is correct: Diseases, insects, and nematodes are living biological agents. Resistance against them is termed biotic resistance.
- Nutrient deficiency in the soil is incorrect: Nutrient deficiency is a chemical constraint of the soil, falling under abiotic stress.
- Water-logging and frost conditions is incorrect: Water-logging and frost are physical climatic conditions, classified as abiotic stresses.
Key Takeaway:
Biotic resistance combats living threats (pests, pathogens), while Abiotic tolerance combats non-living environmental threats (drought, salinity, temperature).