ASRB NET flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Heritability

The proportion of total phenotypic variance attributable to additive genetic variance; determines how much selection response a breeder can expect per generation.

Cytoplasmic male sterility

Maternally inherited failure to produce viable pollen, used to make hybrid seed without hand emasculation; restorer genes in the male parent restore fertility in the F1.

Koch's postulates

Four steps linking a microbe to a disease: constant association, isolation in pure culture, reproduction of symptoms on inoculation, and re-isolation of the same organism.

Climacteric fruit

Fruit that shows a burst of respiration and ethylene at ripening, such as banana, mango and tomato; ethylene treatment can synchronise ripening.

Selection response formula

R = i·h²·σP, where i is selection intensity, h² heritability and σP the phenotypic standard deviation; it predicts genetic gain per generation.

Rumen microbial protein

Protein synthesised by rumen microbes from ammonia and amino acids, then digested in the small intestine; it supplies most of the amino acids to ruminants.

Modified-live vaccine

A vaccine containing attenuated live organisms that replicate in the host, producing strong and durable cell-mediated and humoral immunity.

Somatic cell count

A milk measure of white cells and epithelial cells; elevated counts indicate udder inflammation and are used to monitor mastitis at herd level.

Cation exchange capacity

The total negative charge of a soil expressed in cmol(+)/kg, indicating how many exchangeable cations the soil can hold and supply to plants.

Available water capacity

Water held between field capacity (about −33 kPa) and permanent wilting point (about −1500 kPa); the portion of soil water plants can actually extract.

Nitrification

Microbial oxidation of ammonium to nitrite by Nitrosomonas and then to nitrate by Nitrobacter; the process acidifies soil and nitrate is easily leached.

Base saturation

Exchangeable basic cations (Ca, Mg, K, Na) expressed as a percentage of total cation exchange capacity; low values indicate acidic, leached soils.

Tractive efficiency

Drawbar power divided by axle power of a tractor, expressing how much engine power reaches the implement as pull rather than being lost to slip.

FAO-56 Penman-Monteith

The standard equation for reference evapotranspiration from weather data; crop water use is estimated as ETo multiplied by the crop coefficient Kc.

D-value

The time at a specified temperature needed to reduce a microbial population by 90 percent; used to design thermal processes in food engineering.

Universal soil loss equation

A = R·K·LS·C·P, estimating long-term average annual soil loss from rainfall erosivity, soil erodibility, slope, cover and conservation practice factors.

Gross margin

Gross output minus variable costs for an enterprise; fixed costs are excluded so enterprises can be compared on returns to limited resources.

Net present value

The sum of discounted future benefits minus discounted future costs; a positive NPV means the investment earns more than the opportunity cost of capital.

Coefficient of variation

Standard deviation divided by the mean, expressed as a percentage; used to compare variability between trials whose means differ in size.

Randomised block design

An experimental layout where heterogeneous land is divided into blocks and all treatments are randomised within each block, removing block effects from error.

Water activity

The ratio of vapour pressure of water in a food to that of pure water; below 0.6 most microbial growth stops and shelf life lengthens.

HACCP

A preventive food safety system with seven principles, from hazard analysis and critical control points through monitoring, corrective actions, verification and record keeping.

Maillard reaction

Non-enzymatic browning between reducing sugars and amino groups, producing colour and flavour compounds; accelerated by heat and intermediate moisture.

Casein micelle

The colloidal calcium phosphate-protein complex in milk that coagulates at about pH 4.6 or with rennet, forming the curd in cheese and yoghurt making.

Counter-current gas exchange

Water flowing over fish gills in the opposite direction to blood flow, maintaining a concentration gradient that maximises oxygen uptake.

Unionised ammonia toxicity

The NH3 form of ammonia is far more toxic to fish than NH4+; its share rises with pH and temperature, so high pH worsens ammonia stress.

Composite fish culture

A polyculture of surface, column and bottom feeding species such as catla, rohu and mrigal, using all pond niches to raise total yield.

Induced breeding

Injection of pituitary extract or synthetic hormone to trigger ovulation and spawning in captive fish that would not breed naturally in ponds.

Agrisilviculture

An agroforestry system combining crops with trees on the same land, providing fuel, fodder and shade while improving soil organic matter.

Biomagnification

The increase in concentration of a persistent pollutant along a food chain, as seen with DDT and methylmercury in top predators.

Biological oxygen demand

Oxygen consumed by microbes decomposing organic matter in water over five days; a key indicator of organic pollution in effluents and rivers.

Minimum support price

A price announced for major crops to protect farmers from a market crash; it is recommended by the CACP and backed by government procurement.