Annals of Arid Zone16(4), 427432, 1977 Studies on the breakdown of male sterility in some male sterile lines of pearl millet (Pennisetum typhoides) under conditions of arid zone M.B.L. SAXENAAND B.S. CHAUDHARY Central Arid Zone Research Institute, Jodhpur (Received on 17.5.1977) ABSTRACT The expression of stability in eight male sterile lines of bajra in relation with temperature, relative humidity, day length and rainfall were studied during kharif1974 and 1975. M.S. lines 23D 2 A, 1OIA,I11A and 239D 2 A gave out pollen shedders and the frequency was very low in the second year. Correlations for temperature (positive) and relative humidity (negative) with pollen shedding plants were found significant. Negative correlations for day length and rainfall were"however, non significant. INTRODUCTION The stability of male sterile character of female lines is the requirement of hybrid seed production in crop like bajra. According to Mehta (1968) and Mehta and Murthy (1969) the intensity and percentage of restoration of fertility varies in different agroclimatic regions and from season to season. Burton (cf. Mehta and Murthy, 1969) observed that in pearl millet some florets of male sterile lines at a time shed pollen but if these florets of male sterile lines are bagged, such pollen proves to be ineffective; such behaviour of pollen may be due to the influence of environment. The role of environment in relation to p) lien shedders has not been investigated well. Pollen shedding nature of Tifton 23A, the first utilized mal.: sterile bcdro line in India for the production of high yielding hybrids, was reported by Mehta and l\hrthy (1969) and Vittal Rao (1969). A number of new male sterile lines of bajro have been developed and some of them have been utilized in the production of high yielding hybrids such as PHB 1, PHB 14, J 127, etc. It is likely that others may also be utilized in future. A study was, therefore, planned to examine the stability of expression of male sterility in some male sterile lines.
428 M.B.L SAXENA AND B.S. CHAUDHARY MATERIAL AND METHODS Eight ludle sterile lines of 6('1ra. namely 23A, 23D2A, 67A, lola, lila, 239D2A, Sereno IOLA and 57JA alongwith their maintaining lines were sown during kharif 1974 and part o[the same material during kharif 1975 at Cerural Arid Zone Research Institute, J Ddhpur. Each variety was sown in four rows of 6m length. All the plants in each variety were examined for fertility restoration and its pattern. The percentage of pollen shedding plant was noted weekly. The ears wers selfed and their pollen grains were dusted on their counterpart male sterile plants to know the variability of pollen grains. vveekly data on temperature, humidity, rainfall and the day length were recorder! and their correlations with pollen shedding were worked out. RESULTS AND DISCUSSION Among the eight male sterile lines, four, namely 23D2A, IOIA. II la, 239D 2 A had pollen shedding plants and the percentage found was It3., 12., 146 and 2. respectively during kharif 1974 (Table 1). This suggests that diff<:rent male sterile lines react differently under the same environmental conditions. The data on the percentage of pollen shedders in kharif 1974 and 1975 presented in Table I indicate that the same four lines were pollen shedders in kharif 1975 also, although in very low frequency, i.e. 2.6,.6, 1.3 and 4.1 Table 1. Percentage of pollen shedder plants III different male sterile lines of bajra during kharif 1974 and ]975 S. No. Name of male sterile line Percentage of Pollen shedders 1974 1975 1. 23 A.. 2. 23 D2A 18. 2.6 3. 67 A.. 4. 11 A 12..6 5. llla 14.6 1.3 6. 239 D 2 A 2. 4.1 7. Serere lola.. 8. 571 A..
STERILITY BREAKDOWN IN PEARL MILLET: o:r29 per cent respectively, whereas the other four namely 23A, 67 A, Serere lola and 57lA remained quite stable in both the seasons. It shows that the number of pollen shedder plants in a male sterile line varies from season to season. This is in congruence with the studies of Mehta and MUTlhy (1969). No information is available on the pollen shedding nature of 23D 2 A, lola, IlIA and 239D 2 A. However, Mehta (1968) and Mehta anr1 Murthy (1969) and ViI tal Rao (1969) have reported the pollen shedding nature of Tift 23A. It is interesting that this line was found stable in two seasons. It was also observed that selfed ears and crosses attempted with the pollen of pollen shedding plants formed normal seeds which germinated well. This confirms the fertility of pollen and this observation is in contradiction with the studies made by Burton (cf. Mehta and Murthy, 1969). According to Allard (196) pollen shedding in cytopbmic male sterile lines may be due to the effect of environment, the interaction between the cytoplasm and genotype, the influence of modifier genes and the transfer of maintainer cytoplasm or impurities to the male sterile lines through the maintainer pollen. The impact of environment can be studied by planting of same lines in different seasons. Balrami Reddi and Reddy (197) reported that environmental factors, pajticujarly high day and night temperatures coupled with low relative humidity prevailing in summer and kharif season seem to I:e congenial for throwing pollen shedders in Tift 23A. However, they did not take into account the other factors such as rainfall and day length which have been considered in this study. A perusal of the components in Fig. I reveals that temperature and day length, particularly from the third week of August to fourth week of September, were highft in 1974 than those in 1975. Actu;\lly, those were the weeks when male sterile lines Howered and variation in that period could show the effect in stability of male sterile lines So. correlations between the above four environmental factors and pollen shedder planls have been worked OUI and presented in Table 2. Relative humidity, day length and rainfall were found to have negative correlations with percentage of pollen shedders while temperature showed positive correlation. The correlations with temperature and relative humidity were found to be significant. Thus, with the increae in temperature, the percentage of pollen shedder plants increased and with the increase in relative humidity, it decreased. As such, the fluctuation of these two factors can be predictive for the behaviour of unstable male sterile lines of bajra. Arid areas where weather is always unpredictable and the temperature invariably remains high during the flowering time, there is always pcssibility of
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432 : M.B.L. SAXENA AND B.S. CHAUDHARY the breakdown of stability of male sterile lines. So it will be risky to take up or plan hybrid seed prcduction of bajru in such areas. ACKNOWLEDGEMEl'\TS The authors are grateful to Dr. H. S. Mann, Director for facilities and encouragement. Our thank! are due to Dr. A.Krishnan, Head, Division of Wind Power and Solar energy for providing the meteurological data and to Shri G.V. Subba Rao for help in th analysis of data. REFERENCES Allard, R. W. 196. Principles of Plant Breeding. John Wiley and Sons Inc., New York & London, 485 pp. Balrami Reddy, B. and Reddi, M. V. 197. Studies on the breakdown of male sterility and other related aspects in certain cytoplasmic male sterile!ires of pearl millet (Pennisetum typhoides S. & H.). Andhra Agric. J. 17 (6): 173 18. Mehta, Y. R. 1968. Stability of male sterile lines. Paper Presented at All India.Alillet Improvement Workshop, New Delhi. Mehta, Y. R. and Murthy, C. S. 1969. Male steriles nd problems of seed production. Paper presented at All India Millet Improvement Worhhop, Bangalore. Vittal Rao, S. 1969. An unusual occurrence of breakdown of male sterility in bajra. Andhra Agric. J. (6(1) : 15.