Genetic effects conferring heat tolerance in upland cotton (Gossypium hirsutum L.)
Nov 29, 2019
Cotton belongs to family Malvaceae containing more than
200 genera and about 2 300 species. There are more than
50 species of Gossypium reported till now, which are native
to Africa, Australia, Central and South America and Asia,
respectively (Fryxell 1992; Wendel and Grover 2015). Out
of 50 species, only four are domesticated and widespread.
Two diploid (2n = 26) species, namely G. arboreum and G.
herbaceum belong to Old World cotton produce only 1%
of the total cotton production in the world, whereas two
tetraploid (2n = 52) species, namely G. barbadense and G.
hirsutum belong to New World cotton produce 94% of the
total world cotton production. G. barbadense produces 4%,
while G. hirsutum also known as upland cotton produces
about 90% of the total cotton production in the world (Lu
et al. 1997; McCarty et al. 2004).
Upland cotton is a key source of spinnable fiber and cultivated
in more than 61 countries in the world on an area of
29.3 million hectares (ICAC 2018). Cotton and cottonbased
industry has a pivoting role in the economy of
Pakistan. Pakistan ranks the fourth in terms of area and
production in the world after India, China and USA, 3rd in
consumption and 2nd in yarn production in the world.
Cotton contributes 1% share in GDP, while 55% in total foreign
exchange earnings of Pakistan. Cotton was planted on
an area of 2.7 million hectares in 2017, showing an increase
of 10% over the previous year. About 8% more cotton production,
i.e., 11.54 million bales was recorded during 2017/
2018 as compared with 2016/2017 where 10.72 million
bales was recorded (PCCC 2017). However, in terms of per
acre yield (679 kg·hm− 2), Pakistan is lagging far behind
from the major cotton producing countries like Australia
(1 816 kg·hm− 2), China (1 719 kg·hm− 2), Turkey (1 826
kg·hm− 2) and USA (985kg·hm− 2) (ICAC 2018).
A loss of about one-third of cotton produce was recorded
in Pakistan during 2015/2016 due to adverse climatic conditions
particularly heavy rains during reproductive phase
of crop. But high temperature with dry weather conditions
favored the spread of whitefly in 2016 and 2017 which affected
the productivity of cotton crop on a wide range of
area in Punjab province. In recent times besides drought,
salinity, insect pests, diseases and seed quality: high
temperature has emerged as a major threat to cotton productivity.
It is estimated that the global temperature is increasing
by 0.4~0.8 °C/year (PMD 2016). The consequences
of high temperature in cotton could be low germination,
higher fruit shedding (≥ 30 °C/22 °C), pollen sterility and
abortion (Guilioni et al. 1997; Ismail and Hall 1999), unavailability
of macro and micro nutrients due to increase in
soil pH, higher levels of CO2 in the air will increase photosynthetic
activity resulting in enhanced nutrient requirement
of cotton plants.