| Induced genetic variability for certain physical characters
of grains following gamma-irradiation at two different seed moisture contents
in wheat, Triticum aestivum, var. K-68 Rishi Muni SINGH and Devendra KUMAR* Department of Genetics and Plant Breeding, Banaras Hindu University, Varanasi-221005, (U.P.), India Introduction From the view point of genetic improvement, quality in wheat is considered as complex as the yield. Physical characters (like grain hardness and specific gravity of grains) and certain other factors greatly influence and contribute to the grain quality. For instance, intercellular structure of endosperm determines the milling quality of floor which is associated to the specific gravity of grains. Further, the specific gravity of grains is related to grain texture. (SHOLLENBERGER and COLEMAN 1926). Hard wheats, generally rich in protein with strong gluten are consumed for chapatimaking purposes, whereas soft wheats, generally low in protein with weak gluten are mainly consumed for secondary purposes (bread, bakeries etc.). Thus the grain hardness in wheat determines its use for various domestic and industrial purposes. In soft wheats the flour yield is very low as compared to hard wheats indicating a positive relationship between grain hardness and the flour yield (MOSS and STEVERT 1971). Hardness of grain is also important for proper loaf texture and dough handling characteristics. Further, SYMES (1969) has shown that genes conferring hardness are strongly associated to the loaf texture and dough handling characteristics. In addition, thousand grain weight is associated with the flour recovery. There seems to be limited variability for some of the physical characters of grain in natural wheat populations. The present investigation was therefore initiated to determine the magnitude of variability induced in physical characters of grains using different doses of Co60 gamma-rays at two different seed moisture contents in bread wheat, Triticum aestivum, var. K-68 and to study the degree of correlation and correlated response between pairs of characters. Materials and Methods Seeds of bread wheat, Triticum aestivum, var. K-68, having 14 and 4 per-cent moisture contents were exposed to 5, 10, 15 and 20 Kr doses of Co60 gamma-rays. Irradiated seeds alongwith control were sown in field. Morphological abnormalities, sterility and chromosomal aberrations were used as the basis of selection of plants in M1 generation and superior plant type in the M2 generation. Eighteen mutant lines (stabilized in M3 generation) alongwith the control were grown in M4 generation (1972-73) in a Randomized-block-design with three replications using the plot size of 10 sq. meter. A random sample of ten plants from each plot was used for taking observations on different characteristics. Specific gravity of grains was determined following the procedure of ANAND et al. 1970, and grain hardness by using "Hardness Tester" (Manufactured by Kiya Seisakusha Ltd., Tokyo, Japan). Both, test weight (1000 grain weight) and grain yield (per plant) were determined in gms. Data was subjected to statistical analysis in usual manner. |
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