A comparison of physiological and yield characters in old and new wheat varieties

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Abstract
The Indian subcontinent has witnessed a spectacular improvement in yield of wheat during the past decade (Rao, 1978). This is reflected in the improvement of the average national yields as well as of those regions where wheat is grown as an irrigated crop (Sinha & Aggarwal, 1981). However, after the release of the double dwarf variety Kalyansona, only marginal improvement in yield has occurred in recent years. Despite this, the semi-dwarf character continues to be considered a major factor for improvement of wheat. Asana & Chattopadhyay (1970), Konar & Asana (1975), and Wattal & Asana (1976) observed no significant difference in yield between tall and semi-dwarf (medium tall) varieties in pot culture experiments where lodging was prevented and competition was partly reduced. They ascribed prevention from lodging and improvement in the ratio of grain to total above-ground dry matter as major advantages in the modern varieties. Somewhat similar conclusions have recently been drawn by Austinet al.(1980). However, a detailed comparison of various physiological and biochemical characters lias not been made to determine whether any advance has occurred in basic processes such as photosynthesis and nitrogen assimilation. The present study was an effort in this direction.