THE EFFECTS OF RADIATION ON POPCORN (Zea mays v a r . praecox S t u r t)

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Date
1993-08
Authors
ADAMU, ABU KASIMU
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Abstract
Air dried seeds of inbred line of popcorn (Zea Mays Var. Praecox Sturt) were irradiated with gamma rays (cobalt 60) at the doses of 10,20,30,40 and 400 Gray (gy) and thermal neutrons at 25,40,50,65 minutes 4 -2 -1 and 12 hours with a flux of 1.5 x 10 n.cm . S and sown in the field, laboratory and green house. Result of these treatments, demonstrated a drastic reduction of seed germination, seedling height, root length, and seedling survival. The reduction was positively associated with the dose in both M and 1 M generation. However, there was a slight increase of 2 seed germination in M , raised from treatment at higher 2 doses (t400Gy and N12hrs) of M generation. 1 Among the induced dorminant seedlings mutants, are the occurence of sectors of chloroplyll abnormalities (albina, xantha virescent; lustescent; chlorina and striata) and other morphological changes in appearance; most of which are lethal or unfavourable to growth in both M and M generation. The mean number of mutants per 1 2 mutation were found to be 7.05 in gamma rays and 6.15 in thermal neutrons. The capacity of favourable mutants induced include increase in tiller formation, number of cobs per plants; increased earliness; earlength; and seed weight in most of the treatments. The increase were in direct proportionality with the dose and were more frequent in gamma rays than in thermal neutrons. The class of dominant mutants observed at maturity, include traits such as tassel seed, male sterility and morphological traits not expressed in the seedling stage. However, most of the classes were not transmitted to M generation and the highest percentage 2 observable was not more than 4% in both gamma rays and thermal neutrons and were mostly confined to higher doses. There was also no correlation between the group of mutation (Chlorophyll deficient) observed and male sterility; and not only the frequency is independent of the degree of male sterility, but also the spectrum of chlorophyll mutation does not indicate any connection with M and M male sterility. 1 2 The frequency of mitotic and meiotic aberrations induced include, formation of multivalents(translocation), non pairing, laggards; fragments; eliminated; nonoriented chromosomes, single and dicentric bridges (inversions), induced deformed and aborted pollen grains at different doses in both M and M generation. 1 2 Thus considering the total results on the capacity of favourable mutants; genetics and cytogenetics of gamma rays and thermal neutrons induced mutations seems to be of practical values. In particular the increase in the number of tillers, cobs, earliness, male sterility, ear length, seed weight are beneficial chracters which could be exploited and utilized for breeding of popcorn.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE (M.Sc) IN BOTANY AUGUST, 1993
Keywords
EFFECTS,, RADIATION,, POPCORN, (Zea mays,, v a r ,, praecox S t u r t)
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