Pasture Species Selection and Breeding

This set covers pasture species types, the selection framework for improved species, breeding methods, endophyte management, and seed technology based on the lecture transcript.

What is the definition of a native pasture?

A pasture or feed base containing mostly native species that existed in Australia before European settlement and have not been selected for or bred.

What are some examples of native pasture species mentioned in the transcript?

Wallaby grass, kangaroo grass, black spear grass, Mitchell grass, red grass, and weeping grass (Microlina).

How is a naturalized pasture defined?

A pasture consisting of introduced species that have become naturally adapted to the system and do not require active management to survive.

Give examples of species that can become naturalized in Australia.

Phalaris, subclover, medic (in the south), and buffel grass (in Queensland).

What are the primary reasons native species are well-adapted to the Australian landscape?

They are generally perennial with deep roots, allowing them to cope with low fertility, low soil moisture, and high climatic variability.

What is the typical biomass production of a native species compared to an introduced species?

Native species grow approximately $2$ to $3\text{ tons}$ of biomass, while introduced species can grow $6$, $8$, or $10\text{ tons}$.

What are the three components of the hierarchy for selecting an improved pasture species?

1. Climate (Rainfall and Temperature), 2. Soil Type (Texture and pH), 3. Intended Purpose (Animal type and duration).

What was the driest year recorded for Armidale according to the lecture, and what was the rainfall total?

$2019$ was the driest year with $280$ to $290\text{ mils}$ of rainfall.

What is the trade-off between leaf size and persistence in white clover cultivars?

Increase in relative leaf size is associated with a decrease in relative stolon growing point density, meaning larger-leaved varieties are generally less persistent.

What are the two main types of forage crops?

Brassicas (such as leafy turnip and kale) and cereals (such as oats, rye corn, or wheat).

What is pasture cropping?

Sowing a winter active species like ryegrass or oats into summer active tropical pastures (like Kikuyu or Paspalum) during autumn to balance the feed year.

In terms of breeding, what are the three main regions from which Australian germplasm was selected?

1. Mediterranean region (temperate grasses/legumes), 2. Central and South America (tropical legumes), 3. Eastern and Southern Africa (tropical grasses).

What is the approximate time and cost required to run a new plant line through the evaluation process?

$12$ to $15\text{ years}$ and an investment of $\text{\$10}$ to $\text{\$20 million}$.

How does ploidy affect ryegrass cultivars?

Tetraploid varieties (with $4$ chromosomes per cell) tend to grow faster and have higher quality than diploid varieties ($2$ chromosomes), but may not last as well under grazing.

What are endophytes?

Symbiotic fungi that live in plant cells (specifically ryegrass and tall fescue), producing alkaloids that protect the plant from herbivory but can be toxic to livestock.

What is the difference between wild type and novel endophytes?

Wild type endophytes cause health issues like ryegrass staggers or fescue foot; novel endophytes are selected to provide pest resistance and heat tolerance without the animal health issues.

What are the specific storage requirements to maintain endophyte survival in seeds?

Storage at temperatures less than $5^{\circ}\text{C}$ and seed moisture below $11\%$.

How can seed coatings affect the actual amount of live seed purchased?

Seed coatings (often lime) can increase seed weight by $100\%$ to $500\%$, meaning the actual number of live plants per kilogram is lower compared to bare seed.

What alkaloid is beneficial for pest protection but not toxic to animals?

Peramine.

What alkaloid causes ryegrass staggers in animals?

Lolatrim B.