Abstract
AbstractPot culture experiment was conducted in the Rabi seasons of 2001 and 2002 in order to study the genotypic differences in grain growth rates and endogenous hormonal contents in the developing grains. The hexaploid new plant types and extant variety and other tetraploids are taken up for the study. The data on yield and yield components show that the tetraploids had higher ear number per plant but lesser number of seeds per ear and lower seed weight per ear. The most important yield component 1000-grain yield was also possessed by hexaploids. The mean plant height was found to be higher in hexaploids over tetraploids in general, and among them DL- 1266-1 and DL-1266-2 (new plant types) recorded higher plant height. Similarly, the ear length was also higher in these new plant types. But, the tiller number/plant and ear number/plant were significantly higher in tetraploids. The new plant types (hexaploids) possessed maximum grain growth rate at 5–15 DAA. DL-1266-2 recorded highest grain growth rate 0.093 g/g/day. The photosynthetic rate values show that the hexaploids possessed higher rate than tetraploids. At 7 and 15 DAA, in general, photosynthetic rate was more when compared to 25 DAA and 35 DAA. The results showed that the endogenous hormonal contents in grains during grain development had changed in sequence. At 7 DAA, gibberellic acid (GA3) content was at maximum and at 15 DAA (rapid growth phase), indole-acetic acid (IAA) reached maximum and at 25 DAA (dough stage), ABA was at the maximum. At the 35 DAA, ABA reached all time high and GA3 the least, IAA being intermediate. Among the genotypes, hexaploids recorded higher concentrations of endogenous hormones. The total chlorophyll content in flag leaves of hexaploids was higher than tetraploids. The mean total chlorophyll had increased slightly at 20 DAA when compared to 10 DAA and it decreased at 30 DAA. It appears that the high yielding hexaploids (DL-1266-1 & Dl- 1266-2) by the virtue of possessing more 1000-grain weight and leaf area along with endogenous hormones might be responsible for higher yield as compared to tetraploids. It appears that better photosynthetic rate and better mobilization of photosynthates during grain filling stage contributes for higher yield in hexaploids.
Highlights
The success of food grain production in India over the years is attributed mainly to the performance of wheat crop
Results of Asthir et al (1998) revealed that gibberellins and cytokinins act as positive modulators of grain sink activity, whereas, abscisic acid (ABA) acts as a negative modulator
Ober (1991) demonstrated that ABA could be translocated from leaf tissue to grains and acts as a sensory link between developing reproductive structures and maternal tissues deprived of water and ABA may influence early establishment of sink size through regulation of cell number
Summary
The success of food grain production in India over the years is attributed mainly to the performance of wheat crop. Wheat is the most important Rabi season crop in the country, occupying about 50 per cent of the total area under food crops and accounting for more than 70 per cent of the total grain production in Rabi The present world wheat production is about 600 million tonnes. During the crop year 2000, India harvested 75.57 million tonnes of wheat and for the last four years it is the second largest producer of wheat in the world (Anonymous, 2002). The commercially grown hexaploid bread and tetraploid pasta wheat occupy one fourth of the world’s cultivated area and account for 30 per cent of total world grain production (Salunkhe et al, 1985)
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