Evaluation of High Yielding And Drought Resistant Canola Cultivars in Pothwar

Abstract

Evaluation and selection of improved varieties in accordance with local climatic and soil conditions is one of the important agronomic practices for obtaining higher yields under rainfed conditions. Uncertainty of rains and moisture availability in rainfed areas affect crop growth, development, yield and quality of produce. The information about morphological and physiological characteristics, leaf water contents and seed quality of various traditional and canola type brassica genotypes are helpful in determining the relationship between these characteristics and the varietal performance under rainfed conditions. Genotype-environment interaction is a key assessment tool of crop variety performance. Selection of the best cultivar of a particular crop is an important input which geared revolution in many countries of the world like other factors contributing towards higher yield such as quality seed, judicious use of fertilizer and proper irrigation practices. Adoption of the cultivars with higher yield potential and wide range of adaptability to edaphic and climatic conditions is essential for increasing yield per unit area ultimately boosting up total production. Canola type species presently under cultivation respond differently in different agro-ecological zones as these have been bred under low temperature conditions where it rises smoothly during the period from flowering to maturity. In contrast, under our situation sharp increase in temperature from flowering to maturity not only hastens maturity but also causes flower abortion, shattering of siliqua, less quantity of oil accumulation with low quality oil. The variations in day and night temperature at which crops are grown have decisive effect on yield and quality of produce. It influences the production and utilization of biochemical compounds and energy required for plant growth as each phase of crop growth has critical low and high temperature threshold. Thousand seeds weight, seed yield as well as oil content of canola are influenced by temperature fluctuations. Longer reproductive phase and cooler temperature at the time of seed development stage of crop is favorable for high seed yield. The present experiments were conducted under reasonably wide range of soil and climate. Though average temperature fluctuations are not much higher yet range of minimum and maximum temperature, rainfall and soil variations are noticeable.

Temperature variations at germination, establishment and maturity do effect significantly. To study environmental variation effects on canola three experiments were conducted one each at University of Arid Agriculture, Rawalpindi, Groundnut Research Station, Attock and Barani Agricultural Research Institute, Chakwal having high ( 1000-1200 mm), medium (650-850 mm) and low (450-550 mm) rainfall, respectively, during three years (2003-06). The experiments were arranged in a randomized complete block design with four replications in a net plot size of 5 x 2. 7 m2. The experiments were sown at three locations on 14-10-2003, 13-10-2003, 16-10-2003 at Rawalpindi, Attock and Chakwal, respectively, during first year (2003-04), on 28-10-2004, 14-10-2004, 16-10- 2004 at Rawalpindi, Attock and Chakwal, respectively, during second year (2004-05) and on 07-10-2005, 14-10-2005, 15-10-2005 at Rawalpindi, Attock and Chakwal, respectively, during third year (2005-06). Recommended dozes of fertilizer at the rate of· 80-40 NP per hectare were applied at the time of last plowing. Crop was monitored throughout the crop growing season. Growth and development related parameters were recorded during the crop life cycle. Yield and yield components were recorded at the time of maturity. At maturity central two rows were hurvested manually on 06-04-2004 from Rawalpindi, 01-04-2004 from Attock, 03-04-2001 from Chakwal during first year (2003- 04), on 20-04-2005 from Rawalpindi, 16-04-2005 from Attock and 19-04-2005 from Chakwal during second year (2004-05), 05-04-2006 from Rawalpindi, 10-04-2006 from Attock, 12-04-2006 from Chakwal, during third year (205-06). Results revealed significant variations for characteristics, such as plants per unit area, plant height, number of primary branches per plant, number of secondary branches per plant, number of siliqua per plant, number of seed per siliqua, thousand seed weight, biological yield, seed yield, relative water contents, oil content, glucosionlate content, oleic acid, linolenic acid and erucic acid, among cultivars, locations years and interactions. The significant variations observed for different characteristics may be the combined effect of temperature, moisture availability and soil where crop was grown. Soil temperature varies from location to location and from year to year. Soil temperature has a great influence on germination, emergence and early leaf development. It has been observed that the percent germination is greatly influenced at temperature below 10 °c. Moisture availability during crop life cycle may also be one of the factors affecting crop

at different stages as some crop stages are more vulnerable to stress as compared to other. During seed development a number of quality changes occur before the final chemical composition of the mature seed is realized. There are three factors during the crop reproductive stage with major impact on the level of oil found in canola crop. These are; varieties, soil moisture and temperature. These factors can be controlled to a large extent by selecting the appropriate variety and time of sowing in any region. Among the environmental factors those regulate oil concentration, temperature is one of the most important one. High temperature reduces oil content, however, irrigation may increase oil concentration by mitigating temperature effects. Oil contents are correlated with cooler spring temperature and higher spring rainfall. Oil contents were the lowest, on average, in canola grown in dry years or from the hotter regions and were the highest in canola from cooler and wetter regions. Similar trend has been observed from present experiments. An inverse relationship exists between oil and protein concentrations. High temperature increases protein while decreases oil. Inverse relationship between oil and protein during three years of experimentation and mean oil and protein at three locations during three years was observed in present study. Quality of oil based on fatty acid profile i.e. oleic acid, linolenic and erucic acid have been considered to be affected by temperature and availability of moisture during flowering to maturity. Location which recorded less mean maximum and minimum temperature during flowering to maturity accumulated higher percentage of oleic and less of those linolenic and erucic acid. The contents of saturated and mono saturated fatty acids in seed oil increased when seed developed under high temperature. Both temperature and duration of exposure to the temperature during seed development affected the fatty acid composition of the seed.