| Again from the data given in Table 1 it will
be seen that pollen fertility was reduced in the treated material particularly
at higher doses. Thus it was observed that the maximum reduction in the
pollen fertility with 10,000r gamma-rays is caused in the vars. C591 and
Malvi Ekdania. This reduction is almost equal in the vars. R. S. 31-1, R.
S. 9-11 and Jaipur Local which is 77-78% and is minimum in the vars. Kharchia
and Malvi Ekdania at the 20,000r dose treatment. The reduction in pollen
fertility ranges from 68-70 per cent in all the varieties except Malvi Ekdania
(4x) where it has further reduced to 61% at the 30,000r dose of gamma-rays.
The X-ray treatment which was given in a single dose of 16,000r to only
two varieties R. S. 31-1 and C591 shows a difference in the reduced pollen
fertility viz. 85% in the first variety and 91% in the latter. In pile neutron
treatments with only three varieties R. S. 31-1, C591 and Malvi Ekdania,
the various differences are noticeable in respect of various doses and varieties.
The minimum dose 1.5x 1012np/cm2 reduced the pollen
fertility to the same extent of 91% in the two vars. R. S. 31-1 and C591
while in var. Malvi Ekdania it came further down to 81%. Dose 4.5 x 1012np/cm2
reduced the pollen fertility to 86% in R. S. 31-1 ; 88% in C591 and 79%
in Malvi Ekdania. 5.0 x 1012np/cm2 dose reduced pollen
fertility to 88% in R. S. 31-1 and 78% in C591 and Malvi Ekdania both. The
last and heaviest dose 13.5 x 1012/cm2 not only disabled
all the treated seeds for survival in var. Malvi Ekdania but also reduced
the pollen fertility to a considerable extent i. e. to 60% in var. C591
and to 60.3% in R. S. 31-1. Seed fertility was estimated in the irradiated material and their respective controls and results are summarised in Table 1. From the data it will be seen that all the wheat varieties were not equally sensitive to different types of irradiation and to different doses in the same variety of wheat when seed fertility is taken as an index of radio-sensitivity. The 10,000r gamm-ray treatment increased seed fertility by + 5.86% in var. R. S. 31-1 and by +3.06% in var. R. S. 9-11. In other varieties this treatment generally reduced the seed fertility ranging from -3.87% in Jaipur Local to - 13.82% in Malvi Ekdania. The highest reduction due to 20,000r treatment was recorded in var. C591 being 24.25% and lowest in var. R. S. 9-11 which was -0.12%. The 30,000r treatment showed the highest reduction of seed fertility in var. Malvi Ekdania being - 46.74% and lowest as - 10.30% in var. R. S. 9-11. Among two X-irradiations var. R. S. 31-1 showed a reduction of -0.22% while var. C591 showed as high as -25.82%. On viewing the data in Table 1 for effect of pile neutrons comprising of four doses in three varieties. Malvi Ekdania registers an improvement by + 15.04% with 1.5 x 1012np/cm2 dose while in other two varieties this reduction is almost the same being -16.09% in R. S. 31-1 and - 15.62 in C591. With the dose 4.5x 1012np/cm2 the lowest reduction was found in var. Malvi Ekdania (4x) being -0.40% and highest in var. C591 being -21.09%. In the same way var. Malvi Ekdania showed lowest reduction as -8.94% and var. C591 had the highest reduction in seed fertility as -25.52% as far as the dose 5.0 x 1012np/cm2 is concerned. The highest dose of 13.5x 1012np/cm2 being lethal to var. Malvi Ekdania reduced the fertility of seed to the highest level in the other two varieties being - 44.86% in R. S. 31-1 and -30.20% in var. C591. In conclusion the data are suggestive probably of the fact that the superior radioresistance of the hexaploid wheats as regards their survival at the lowest doses of gamma-rays and universally with the four pile neutron doses. This is also true in case of pollen and seed fertility both in regard to the gamma-ray and pile neutron treatments. As reported earlier (CHANDOLA, 1966) that unlike varieties are differently susceptible to irradiation, have at this stage also showed the same variation among themselves. As may of the induced mutations in bread wheats are chromosomal in origin, the aggravation in the amount of chromosomal damages induced by radiations becomes externally visible in subdued survival and pollen and seed fertility since the occurrence of too may chromosomal structural changes might lead to disturbed conditions in the life cycle of plant material under consideration. These conclusions are further supported by the types of mutations obtained in the M2 progenies of these wheat varieties, the data regarding which are intended to be presented in the near future. (Received Jan. 13, 1968) |
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