| Studies on fertility restoration in male sterile wheats
derived from Aegilops comosa cytoplasm M.A. KARIM* and M.P. SINGH Division of Genetics, Indian Agricultural Research Institute New Delhi-110012, India Keeping in view the practical importance of fertility restoration in hybrid wheat programme, studies were initiated to find out specific combination with comosa cytoplasmic background where partial to complete fertility restoration can be obtained. It may be mentioned that the problems of restoration still exists, the restorer so far reported are effective, for certain varieties and with specific alien cytoplasm (WILSON & ROSS 1962 ; TSUNEWAKI 1974, 1980). There is significant fluctuations in their expressions as such more studies in this area would be useful. Materials and Methods Prof. K. TSUNEWAKI (Japan) developed some Chinese Spring alloplasmic lines having Ae. comosa Sibth et. Sm (2n=14 ; MM) cytoplasm in background. These lines were used as cytoplasm donor for the production of male sterile lines in wheat. Twenty four cultivars of common wheat (Triticum aestivum L., 2n=42, AABBDD) were selected as nucleus donors. Series of crosses between cytoplasmic donor as female and nucleus donors as pollen parent were attempted in 1978-79 and subsequently these pollen donors were used as the recurrent male parent in the substitution backcrosses. On each side of male sterile rows one row of corresponding nucleus donor was grown at a distance of 45 cm between the rows and 5 meters long each row. Observations on pollen and seed fertility were taken from different alloplasmic lines for F1 in 1980, BC1 in 1981 and BC2, in 1982 grown at IARI New Delhi farm. For calculating seed fertility in open and selfed (bagged) spikes, average of five main spikes of different plants was taken and then percentage was worked out (KARIM 1982). Prefix 'allo' refers to different male sterile lines having comosa cytoplasmic background. Results and Discussion Normal fertile anthers were noticed in BC2, alloplasmics, comprising of nucleus donors Lal Bahadur, Ridley and HD 1944, where average pollen fertility was recorded as 91%, 32% and 19% respectively. Allo-Lal Bahadur restored pollen fertility (91%) very close to the nucleus donor Lal Bahadur (95%) (Table 1). Pollen fertility observations were further confirmed with better selfed seed set, where allo-Lal Bahadur produced 41%, allo-Ridley had 27% and allo-HD 1944 showed 22% selfed set. Pollen fertility and selfed seed data indicated that Lal Bahadur Ridley and HD 1944 carry weak fertility restoring gene(s). Fertility factors present in variety Lal Bahadur appear to be more active. Cytological studies have revealed that all the three alloplasmic lines possess one additional chromosome in each line, which were transmitted from Ae. comosa alongwith its cytoplasm to wheat background. Allo-Lal Bahadur contained near medium chromosome, allo-Ridley showed sub-median chromosome, where as allo-HD 1944 had terminal chromosome. All these three chromosomes of comosa transmitted separately in three different lines, apparently appeared to have different effects on pollen and seed fertility in these lines. |
| * Present address : Department of Botany, Bangladesh Agril. University, Mymensingh, Bangladesh |
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