Horticultural Crop Development and Yield

Study for Exam

What is Florigen?

A hypothesized molecule that controls and triggers flowering in plants

Is Florigen a hormone?

We don’t know, best we’ve got is hormone-like.

What is Floral Evocation?

When meristematic tissues are IRREVERSIBLY transitioned from vegetative to reproductive phases

What is Floral Induction?

The signal to flower

True or False: The amount of flowering influences crop load

True, do not get this one wrong or I will judge you harshly

True or False: the juvenile phase will be a consistent length between cultivars

FALSE! FAKE NEWS!

What are the primary factors that regulate flowering?

• Hormones like GA and Florigen (hormone-like)

• Sucrose and Carbohydrate levels in apical meristems

• Photoperiod

• Temperature

• Whether the plant has reached a minimum vegetative size

What is vernalisation?

The period of cold required for plants during winter to break dormancy and induce flowering

What hormone is responsible for biennial bearing?

Gibberellic Acid - present in fruit seeds. If there are a lot of seeds on the tree in one year, it will repress flower initiation for the following year. If there are not as many seeds on the tree in that year, there will be less GA in the tree to suppress bud development and the crop will be heavier.

How do we prevent biennial bearing?

Heavy thinning during the heavy year

True or False: Most annuals require a period of cold during winter dormancy for the initiation of flowering

False: Most perennials

In which crop species is photoperiod not a factor in flower initiation?

Most fruit and nut trees

What is responsible for the plant reaction to photoperiod?

Phytochrome

What two factors are necessary for carrots to initiate floral genesis?

Vernalisation and the taproot needs to reach a certain size

True or False: NZ produces around 50-60% of the world’s carrot seed

True

True or False: Carbohydrate levels decrease in shoot apices shortly before initiation of flowering as resources are diverted to axial buds as the apical buds are decommissioned to be turned into flowers.

False: they increase

True or False: Temperature is a direct factor as to how much your plants will bear

True

What are the factors which reduce flower numbers?

• low light levels

• strong vegetative vigor

• high crop loads

• immature growth

• shelter proximity

• closed canopies

• close planting distances

Why is close planting bad for crops?

It can increase the proliferation of pathogens and pests, affect nutrient availability, and shade out most of the vegetative portions of the plant.

Will grafting to a dwarfing rootstock increase or decrease early flowering in apples and pears?

Increase

What defines a dwarf rootstock?

When the rootstock keeps the scion at 15-25% of its size

Why does a dwarfing rootstock provide better fruit?

A larger proportion of the carbohydrates produced will go to the fruit sinks rather than vegetative tissue

What happens if you have a high vigor scion matched with a high vigor dwarfing rootstock?

Too much vegetative growth

What are two factors other than size and vigor to consider when choosing your scion and rootstock?

environmental interactions with cultivars, and disease resistance or vulnerability

Why do we prune and train?

Shading is a key cause of poor flower initiation, so we do this to maximise light interception

What are the benefits of thinning and pruning?

It allows more light to reach lower branches, and may induce more branches to grow which will increase the number of flower buds

What two chemicals are effective in promoting return bloom?

NAA and Ethephon

What is pollination?

The transfer of pollen from the male anther to the stigma to allow fertilisation and production of a seed

How much is the estimated worth of bee pollination in NZ?

NZ $5 billion

What crops are insect pollinated?

Carrot, radish, beet, clover, apples, pears, avocado, blueberries, kiwifruit

What are two methods for artificial pollination?

Wet pollination - spraying pollen solution over an orchard or vineyard
Dry pollination - blowing clouds of pollen over an orchard or vineyard

What are two downsides of artificial pollination?

They are expensive, and can spread disease

What three important crops are unattractive to honeybees?

Carrot, manuka, and kiwifruit

What sort of pollination is essential for cereal crops?

Wind pollination

What two factors are essential for successful pollen germination?

Water for rehydration and pollen recognition

What is Dicliny?

When a plant has separate male and female reproductive parts

What is Dichogamy?

When plants shed their pollen at a different time than their stigmas are receptive to avoid self-pollination

What are some methods to prevent self-pollination?

Dicliny

Dichogamy

Pollen sterility

Incompatibility Alleles

How do incompatibility alleles prevent self-pollination?

They prevent the pollen tube from growing down the style of a plant from the same genotype even if the pollen is viable

What are the factors influencing pollination?

Temperature, humidity, and time

What is the optimum temperature for plum pollen germination?

20 C, but it can range from 10-30C

What temperatures are bees most active in?

10-35 C but optimum is 22-25 C

What % of the world’s flowering plants are wind pollinated?

12%

What sort of weather can prevent pollen shedding in cereal crops?

Cold humid days

How many stamens are in male kiwifruit flowers?

134-182 stamens

How many stigmas are in female kiwifruit flowers?

Up to 41

How many pollen grains do female kiwifruit pistils require to set 700 seeds per fruit?

3000

How many seeds are required per kiwifruit for export quality?

700-1400

How much of the kiwifruit flower must be successfully fertilised for a commercially viable crop?

80-90%

Why does more fertilisation result in larger kiwifruit?

Fertilised seeds have hormones which promote cell division

What is the main pollinator of NZ kiwifruit?

honeybees and bumblebees

True or False: Honeybees are more faithful to kiwifruit flowers than bumble bees

False: Honeybees think kiwifruit is blah, but bumble bees can vibe with it. They will leave kiwifruit hanging for some lupines though

What mite is threatening honeybee hives globally?

Varroa

What management or cultivation tools could prevent good pollination by wind?

Shelter belts could block wind pollen, and so could growing vines closer to the ground

What is the optimum ratio of male vines to female vines for kiwifruit?

Generally, 1:8

True or False: there is no increase in fruit weight or the number of properly pollinated seeds at ratios of 1:3 compared with 1:8 male vines to female in kiwifruit orchards

True

How are male kiwifruit vines situated in relation to female vines?

Every third plant in the row, either above the main crop at right angles to the female vines or in a narrow strip row parallel to the main vines.

What factors can affect the quality of the seed set?

Time, fertilisation percentage, pollen quality, and season

How many pollen grains are needed for full seed set in the Hayward cultivar?

10,600-13,250 or 40 honeybee visits

How many pollen grains are needed for Hort16A cultivar for full seed set?

3,500-4,000 or 6 honeybee visits

True or false: apples are mainly wind pollinated

False, they are mainly insect pollinated with 95% coming from honeybees

What pollinators other than honeybees pollinate apples?

bumble bees and flies

How many seeds per apple?

Generally 10: 5 ovaries with 2 ovules per ovary

How does uneven pollination affect apples?

Misshapen fruit

True or False: It’s better to place hives in long rows for good pollination in apple orchards

False: irregular spacing is better

What is the hive density per hectare for apple orchards?

1-2 hives /ha

True or false: most apples are self-fertile

False, although golden delicious might be

How many male apple trees should there be in a planting section?

the third tree in every third row

What are the two types of biosecurity?

External biosecurity - movement in and out of a country

Internal biosecurity - movement within a country

What act is governs biosecurity in NZ?

The Biosecurity Act of 1993

True or False: NZ Biosecurity is mostly concerned with incoming goods, not so much outcoming goods

False: If we share our bugs with the world, the world will stop buying our stuff

Who are the key players in biosecurity?

Biosecurity NZ through MPI

Industry Organisations - they’ll have biosecurity plans for individual grower systems

Regional Councils

Iwis

Community Groups

Growers - they have to have on-farm biosecurity plans and strategies

The public

True or False: The brown marmorated stinkbug is the only stinkbug variety native to NZ

FALSE! CRUSH IT! CRUSH IT WITH YOUR SHOE AND CALL THE COPS ON ITS ASS!

Where is the Brown Marmorated Stinkbug native to?

SE Asia

How many plants does the Brown Marmorated Stinkbug prey upon?

Over 300 including fruit trees and woody ornamentals

True or False: Brown Marmorated Stinkbug has so far not made it to NZ

False: But it’s been intercepted at the border because of specially trained Very Good Dogs

How did NZ eradicate the Pea Weevil?

They prohibited the growing of any pea crops in Wairarapa for 4 years which starved them out, and set up population monitoring through traps to make sure the area was clean before the ban was lifted

How many growers approximately in NZ?

4500

What is the approximate value of the horticultural industry in NZ?

$7.48 billion

What are the major challenges for the hort industry in NZ?

labour, biosecurity, water, the regulatory environment

What are the two native plants used in commerical ag and hort in NZ?

Manuka and NZ Spinach

What are the largest two exports for the NZ hort industry?

Kiwifruit (54%) and Apples (19%)

How much of the horticulture export revenue comes from fresh and processed veggies?

15%

True or False: Most veggies are grown in NZ for domestic consumption

True

Which veggies in NZ are grown more for export than domestic consumption?

Squash, potato, onion

Why are NZ exports so valuable?

NZ has a reputation for high quality, safe products

What are NZ’s main export destinations?

Asia, UK, Europe, Canada, etc

What country is NZ’s number one competitor for kiwifruit?

Italy

Which ten sectors make up most exports for NZ?

Kiwifruit, grapes for wine, apples, avocadoes, onions, peas, potatoes, veggie seeds, squash, and cherries

What is the scientific name for Avocado?

Persea americana

Where is avocado mostly grown in NZ?

North Island around the Bay of Plenty and far North

How many avocado growers are there in NZ?

899

Why did the avocado market in NZ crash?

The Aussie avocado growers recovered

What is NZ’s main competitor for avocado?

Central and South America

What variety of avocado is the most prevalent?

Haas

What challenges do the avocado growers in NZ face?

Biosecurity issues, dependence on the Australian market, access to skilled labour, improving yields, fruit consistency, quality through the supply chain

Where are cherries grown in NZ?

90% in Central Otago and Hawkes Bay

What percentage of cherry crops are exported?

80%

Who are NZ’s biggest competitor for cherries?

Chile, they can produce much more cheaply

What challenges do cherry growers in NZ face?

Labour at harvest, access to skilled permanent staff, slow development of rootstocks for intensive production methods