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United States Department of Agriculture

Agricultural Research Service

Research Project: Commercialization of New Industrial Crop Germplasm and Cropping Systems

Location: Plant Physiology and Genetics Research

Title: Osmotic stress causes differential effects on germination indices, total soluble sugar, and proline content in different wheat (triticum aestivum L.) genotypes

Authors
item Qayyum, Abdul -
item Razzaq, Abdul -
item Ahmad, Muhammad -
item Jenks, Matthew

Submitted to: African Journal of Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 9, 2011
Publication Date: N/A

Interpretive Summary: Current estimates indicate that 25% of the world’s agricultural land is now affected by high levels of water deficiency. Water deficient environments due to increasing climatological drought, dwindling aquifers, and salinization are among the major causes of crop loss worldwide, commonly reducing average yield for many crops by more than 50%. To determine whether significant genetic variation in traits associated with drought tolerance during early plant development exist in wheat grown in arid and semi arid zones of Pakistan, five wheat cultivars from the Punjab province were subjected to five levels of osmotic stress, and its effect on germination percentage, mean germination time, coleoptile length, and early seedling proline and sugar content was assessed. For all cultivars, germination percentage, mean germination time and coleoptile length were shown to decrease with increasing osmotic stress, whereas proline and sugar content was shown to increase with increasing osmotic stress. The results of this study also show that significant genetic variation exists among these five wheat genotypes for these osmotic stress responses. Previous studies indicate that cultivars that perform best in these assays should also produce the best yields in arid and semi-arid environments. Besides revealing mechanistic determinants of stress tolerance in these wheat cultivars, results here also reveal excellent parental material for use in breeding improved drought stress tolerant wheat.

Technical Abstract: Diverse crop cultivars differ inherently in their response to climatological drought, and those cultivars with the best seed germination and early seedling growth under arid and semiarid conditions form the most uniform and vigorous stands under water deficit conditions. To determine whether significant genetic variation in traits associated with drought tolerance during early development exist in wheat grown in arid and semi arid zones of Pakistan, five wheat cultivars (GA-2002, Chakwal-97, Uqab-2000, Chakwal-50 and Wafaq-2001) from the Punjab province were subjected to five levels of osmotic stress, 0 bars (distilled water), -2 bars, -4 bars, -6 bars, and -8 bars, and the effect of osmotic stress on germination percentage, mean germination time, coleoptile length, and early seedling proline and sugar content was assessed. The investigations were performed as factorial experiments under completely randomized design. Germination percentage, mean germination time and coleoptile length were shown to decrease with increasing osmotic stress, whereas a progressive increase in proline and sugar content was observed with increasing osmotic stress. The response of the five cultivars examined to these various levels of osmotic stress differed dramatically. Chakwal-50 and GA-2002 exhibited a response consistent with best drought adaptation, showing a more rapid germination rate, the longest coleoptile length, and the highest proline and sugar content when compared to the other cultivars under these treatments. By comparison, the Wafaq-2001 and Uqab-2000 cultivars showed the poorest response relative to other cultivars. Clear genetic variation exists among these five wheat genotypes for osmotic stress response, shedding light on which cultivars should perform best in arid and semi-arid environments, and revealing the best parental material for use in a breeding program seeking improved drought stress tolerance.

Last Modified: 10/1/2014
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