Keitt

Keitt is a late-season, semi-dwarf variety with large, highly coloured fruit. Keitt originated in Florida as an open pollinated seedling of Mulgoba, which was first selected in 1939. Keitt is grown commercially in many mango exporting countries, such as the USA, Israel, Mexico and South Africa.

Although Keitt was first introduced into Australia in 1979, it was not widely grown until the late 1980s.

Fruit characteristics

• ground colour - green-yellow
• blush - red-pink to bronze
• weight - 400 g-1 kg
• average length - 130 mm
• average width - 90 mm
• average depth - 85 mm
• lenticels* - medium-large and yellow
• pulp colour - lemon yellow
• skin thickness - thick
• pulp fibre - medium
• firmness - firm
• stem end shape - slightly depressed
• beak shape - insignificant
• shape - ovate*
• pulp recovery - 72 per cent
• flavour - sweet-mild
• embryo type - monoembryonic*.

* Refer to Glossary

Tree characteristics

Keitt grows with low-to-medium vigour as an upright, open canopy. Branches have a natural tendency to grow long and thin, arching to the ground with heavy crop loads if left unpruned. The new leaves are initially a red-brown colour, turning green as they expand and harden. Six-year-old trees can reach heights of 2-5 m with a canopy diameter of 2-4 m.

Propagation

Keitt is a monoembryonic* variety, which means that the seed, if planted, will not produce seedlings that produce fruit true to type. Therefore, propagate the variety by grafting onto a uniform polyembryonic* rootstock. Kensington Pride has been the most widely used rootstock for Keitt. Grafting high on the rootstock helps encourage high branching.

* Refer to Glossary

Plant density

Planting densities in Keitt are generally higher than other mango varieties grown in Australia because of this variety's dwarf low vigour and small tree size. Plant spacing varies between 1.5-6 m in the row and 6-8 m between rows (238-1111 trees/hectare). Because of  the open canopy of Keitt, light penetration and fruit colour is not a problem at higher densities. Because of the open canopy shape Keitt fruit is particularly prone to sunburn.

Pruning and shaping

Keitt is a naturally very open, spreading tree with a few long arching branches. This tree shape does not lend itself to producing good fruit quality or high yields. Problems with tree shape can be overcome by pruning and shaping young trees during the first few years after planting. The first branching of the trunk should be high (1.2-5 m) to prevent fruit from hanging on the ground. To force them to branch often, cut the limbs of Keitt every second growth flush to maximise the number of terminals and fruit-bearing surface.

Keitt trees are slower to grow than other more vigorous varieties, so will take 4-6 years to produce an adequate bearing frame. Forcing growth with nitrogen in the early years can lead to excessive vegetative growth and predispose the fruit to internal fruit disorders.

Pest and disease status

Keitt is susceptible to bacterial black spot, which can cause severe fruit loss if allowed to build up in trees before flowering. Other post-harvest diseases that can affect Keitt are anthracnose (Colletotrichum gloeosporioides), a major cause of fruit blackening, and stem end rot (Botryosphaeriaspp., and Lasiodiplodia theobromae).

Keitt is affected by major insect pests such as mango scale (Aulacaspis tubercularis),tipborer (Penicillaria jocosatrixand Chlumetia euthysticha),fruit flies (Bactrocera sp.) and planthopper (Colgaroides acuminata).

Harvesting and handling

Keitt is a late-maturing variety, generally harvested 4-6 weeks after Kensington Pride. It has a relatively long green mature period before tree ripening occurs, providing an extended harvest window. Harvesting is often carried out over 2-5 picks. Smaller fruit, as long as they are not nubbins, left on the tree will size up when the larger fruit is removed.

Marketing

Keitt is a late-season variety that is marketed in Australia between late January and early April, avoiding the high production glut of Kensington Pride. Keitt has export clearance for Japan after treatment with approved vapour heat treatment for fruit fly disinfestation.

Glossary