Post-anthesis stem reserve mobilization in new plant type wheat
P.C. Pandey, MRS Kaim, S.S. Singh1, G.P. Singh1, D.K. Joshi and A.P.S. Verma
1Nuclear Research Laboratory, Division of Genetics Indian, Agricultural Research Institute New Delhi, India
Post-anthesis stem reserve mobilization is an important assimilate contributing source for grain filling in wheat under temperature stress conditions invariably encountered in major wheat growing regions of the world (AI- Khatib and Paulsen 1990; Blum et, al. 1994). Quick screening of genetic variability in post-anthesis relative stem reserve mobilization therefore, assumes importance for developing improved wheat plant types. Post- anthesis changes in proton relaxation time T1 of wheat stem were suggested to indicate the post-anthesis stem reserve mobilization (Pandey et al. 1998) and also genotypic differences in such mobilization under normal and one month late sown conditions (Pandey et al. 2001). It was also suggested by these authors that thick/hollow stem character, capable of superior storage and post-anthesis remobilization of assimilates may be studied for designing new plant type for increased yield potential. More recently new plant type of wheat with thick stem, improved grain weight and grain number per car has been developed (Singh et al. 2001). It has been suggested that physiologically these new plant type genotypes have developed an improved translocation path up to the individual floret level and an improved pre-anthesis assimilate reserve and its post-anthesis mobilization to the grain. It is in this context, the post-anthesis changes in NMR T1 and moisture percent in the peduncle region of one of the new plant type DL 1266-5 was studied.
The wheat genotype DL-1266-5 (Singh et al. 2001) was sown on 20th November 2001-02 in the field of Indian Agricultural Research Institute. Fertilizers NPK were applied in the form of urea, single super phosphate and muriate of potash @ of 120:60:40. Nitrogen was applied as basal dose (50%) and 50% at crown root initiation stage. Main shoots were tagged at the time of anthesis and were harvested for sampling on the day of anthesis and 2, 10, 16 and 25 days after anthesis (DAA) in moistened polythene bags to avoid moisture loss. Separated peduncle portion, were gently packed in NMR sample tubes (18 mm diam) upto sample height restricted to 20 mm within the homogeneous field of the magnet. T1 was measured by Saturation Recovery method-using software loaded in EDM 511 (supplied with the instrument), which gives a single component with three-parameter fit, by a 20 MHz Bruker minispec pc20 NMR system. The water content was measured in the same samples after measuring T1 by oven drying to constant weight at 85°C.
T1 parameter shows an increase after 10th day of anthesis in
spite of a sharp decline in the moisture percentage (Fig.
1) suggesting a rapid mobilization of stem reserves from stem in this genotype
after 10thday of anthesis under normal sown conditions. These observations tend
to support the suggested efficient post- anthesis mobilization of stem reserve
in the DL 1266-5.
References
Al-Khatib K and Paulsen GM (1990) Photosynthesis and productivity during high temperature stress of wheat genotypes from major world regions. Crop Sci 30: 1127-1132.
Blum A, Sinmena B. Mayor J, Golan G and Shipler L (1994) Stem reserve mobilization supports wheat grain filling under heat stress. Aust J Plant Physiol 13: 771-781.
IARI wheats for evergreen revolution 2001. In: Singh SS and Singh BB (ed) Publ Indian Agric Res Inst, New Delhi- 110012, India: 17-23,66-78.
Pandey PC, Joshi DK,Kumar S and Gambhir PN (1998) Post-anthesis changes in proton relaxation time T1 of wheat (Triticum aestivum L.) stem-A possible in vivo indicator of reserve mobilization. Indian J Exp Biol 36:, 213-216.
Pandey PC, Joshi DK, Sachdeva P and Pathak PC (2001) Desirable traits for tropicalisation of wheat III. Post-anthesis stem reserve mobilization. A new application of in vivo nuclear magnetic resonance technique. Indian J Plant Physiol 6: (NS) 414-415.
Singh SS, Sharma JB, Chand Nanak and Sharma DN (2001) Breaking yield barriers in wheat-new plant type designed. Wheat Inf Serv 93: 22-26.