Researcher | | Onion Onion
is the third most important vegetable crop after tomato and watermelon
globally. In South Africa, onion is the third largest vegetable crop,
following potato and tomato, and the annual production exceeds 500 000
metric tons. In many African sauces, onion is an essential ingredient
and a source vitamins, minerals, trace elements, phenolic compounds and
antioxidantive flavonoids. Onion breeding at the Agricultural Research
Council started in 1947, with the aim of developing improved short-day
onion cultivars. In 1972, a breeding programme for intermediate-day
onions initiated. Improved cultivars were developed by crossing short
and intermediate-day lines, which inherently have multiple bulb scales,
high bulb firmness and uniformity with adaptation to local conditions.
Three open-pollinated short-day cultivars, namely Pyramid (1968), Bon
Accord (1968), and Radium (1987), and five intermediate-day cultivars
namely Roël (1987), Rion-1, Rion-2, Rion-3, and Rion-4 (all in 1992)
were released. In 1980, the breeding of male-sterile and maintainer
lines for both day lengths was initiated. Since then several
well-adapted male-sterile and maintainer lines for both day lengths were
developed. Currently, the breeding program has been limited to
maintenance of the available germplasm. In South Africa, almost
all the onion breeding activities have been done by private seed
companies. The majority of onion cultivars on the market are hybrids,
most of which are imported, and owned by a few seed companies.
Smallholder farmers are not benefitting from the available technologies
because of the high seed price and input requirements of the onion
hybrids. To alleviate poverty and food insecurity in the rural
community, priorities must be given to improve the livelihoods of
smallholder farmers. In recent years, encouraging results have been
observed on home gardening, especially in semi-urban and urban areas
with small plots of vegetables. Farmers grow vegetables such as
cabbages, onions, tomatoes, chilli peppers, carrots and potatoes in
their homesteads for consumption and to earn income. Through a planned
project, the ARC wishes to play a role in promoting small scale
vegetable production by developing low input, improved cultivars,
providing training and technical support. The main objectives of the
onion breeding program will be to develop onion cultivars (new improved
hybrids and open pollinated cultivars) with enhanced bulb yield and
quality, tolerance to heat and drought, as well as resistance to pests
and diseases for both commercial and smallholder farmers. The
onion project at the ARC makes use of molecular markers that facilitate
the selection of male sterile and maintainer parental lines. Male
sterility is important to prevent self-pollination and loss of the onion
hybrid genotype. Classic methods (test crosses) require 4-8 years of
progeny testing before the cytoplasm type can be determined. Accurate
and time-saving PCR molecular markers and custom TaqMan® SNP genotyping
assays were found to be efficient in screening the ARC onion lines
rapidly for their cytoplasmic and nuclear male sterility genotype. The
molecular marker methods are used in the production of the correct seed
for commercialization of ARC onion lines.
Publications:Gazendam
I, Greyling MM, & Laurie SM. 2018. The application of molecular
markers to accelerate the recovery of cytoplasmic and nuclear male
sterility in South African onion hybrid parental lines. Journal of Agricultural Science 10(7): 95-109 Lodama,
K.E., Gerrano, A.S, Laurie, SM., Mavengahama, S. & Adebola, P.O.
2018. Response of prolonged storage time and growth media on seedling
emergence of onion (Allium cepa L.) in South Africa. Acta Horticulturae 1204: 33-39.
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