The climate of the Pakistan is characterised by an arid and semi-arid season, showing deficiency of water for potential crop production. It is estimated that l/4th of the total cultivated land (4.9 millions hectares) is drought-prone (Khan and Qayyum, 1986).
Although the canal system of Pakistan is ranked among the best in the world, but still, vast tracts of Pakistan are solely dependent on rain.
Therefore even under irrigated conditions, availability of water is not ensured for the whole year especially in the Rabi season when the monsoon terminates. The situation has been worsened by the shortage in the water storage capacity due to the deposition of silt in dams.
In a nutshell insufficient rainfall and lack of irrigation water are twin bottlenecks to get the potential yield of Brassicas and other crops as well.
Crops (Brassicas, wheat etc) in rain-fed areas survive on soil-stored moisture and occasional rains, and as the temperature rises in spring and summer, water stress becomes increasingly common during flowering and grain development, and eventually the harvest falls well below its potential.
Brassicas in Pakistan are marginal land crops, which compete with wheat for space and resources, usually they are squeezed out and wheat is the preferred crop.
The situation could be better if high yielding and drought-tolerant Brassicas, with economic return comparable to that of wheat, were available.
This is one of the reasons to explore drought-tolerance in Brassicas. Droughts are not only characteristic of arid and semi-arid climates, water availability is becoming increasingly limited for irrigated agriculture due to increased cropping intensity and the diminishing resources of water.
The edible oil situation in Pakistan:
Pakistan is suffering from a chronic deficit of edible oil production, and to meet the domestic needs, has to depend on imports, which require huge amounts of hard-earned foreign cash. Five years local production, requirement, imports and total expenditure from 1997 to 2002 is presented in the table.
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Years Local Import Total Expenditure
Production (000 tons) (000) Million (Rs)
(000 tons)
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1997-98 518 1178 1696 33304.4
1998-99 531 1325 1832 40535.7
1999-2000 607 1091 1698 21401.9
2000-2001 642 1144 1786 19044.8
2001-2002 646 1185 1831 240.34.3
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DEVELOPMENT OF DROUGHT TOLERANT GENOTYPE: Canola can be grown on irrigated and Barani areas. Canola being low in erucic acid (0.5-2%) and glucosinolates (30 æ molg -1), restricts increase of cholesterol in the blood and other heart diseases.
Canola can be used directly after crushing the seed. Mostly, canola comes from Mediterranean-type climates. Furthermore, canola varieties are low yielders than raya ie, other species Brassica juncea. Keeping all this, we have to create the new variability, followed by selection to get the desirable genotype adjusted to our climatic conditions, which is arid to semi-arid.
To get the desirable genotype, we should know the genetic basis of different traits of canola, helpful to combat the drought.
One of major causes of the low yield of the canola variety in our climate is that Pakistan has a relatively short span of growth period and during the second fortnight of April, the temperatures become too high so that grain filling suffered severely.
Secondly, during March and April, aphid attack becomes a severe problem, which have to be controlled, timely and effectively.
Genetic differences in tolerance to drought offer a unique opportunity to compare changes in the morpho-physiological traits in plants, that might be involved in drought tolerance.
In order to breed tolerant cultivars, an understanding of plant responses to reduced water availability is necessary, so that the tolerance mechanism maybe manipulated.
One solution to the problem is the possibility of developing hybrid Brassicas, possessing, both a high yielding ability and drought tolerance.
The circumstances of edible oil and water deficit urge encourage the breeding of Brassicas, that guarantee high edible oil production through high seed yield, under limited water supply conditions.
To exploit these systems, a study leading to a Ph.D. degree had been launched, for three consecutive years, at the research area of the University of Agriculture, Faisalabad, under the supervision of Dr Hafeez Ahmed Sadaqat (Associate professor, Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad).
A scientific attempt was made to understand the genetic behaviour and response of Brassicas to tolerate drought. Furthermore, it was aimed to search for the genetic basis that imparts drought tolerance, high seed yield and the various parameters that influence, directly and indirectly, yield under drought conditions.
The information, so obtained, would be useful in formulating a selection criteria for drought-tolerance and high yield. The selected types could then be used in a hybridisation programme aimed at breeding Brassicas yielding high, under water-deficit conditions.
According to studies, in our climatic condition, the most suitable variety would be those that have a short vegetative growth period, more primary branches and complete their life cycle before the onset of drought and aphid attack.
This variety would also have a long, viable, extensive root system so that larger volumes of soil could be exploited for the water requirement of the plant.
To get such a variety, one should have crossed the drought-tolerance parents. By crossing such parents, a large amount of variability may be created. Research studies suggested, that for the development of a drought-tolerance variety, choice of cross of Range x Shiralee would be fruitful to select the desirable segregants from the early generations.
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