Pollen production and shedding in male fertility restorer lines of wheat

R. B. SINGH and J. S. SINDHU

Department of Genetics and Plant Breeding, Banaras Hindu University, Varanasi, India

Effective wind pollination is a pre-requisite for exploiting heterosis in wheat. Even though significant yield heterosis is recorded (SINDHU and SINGH 1971), low outcrossing potential of the A and R lines is a barrier in economic exploitation of hybrid wheat. Factors like synchronous flowering of male and female lines, stigma receptivity and pollen shedding are likely to influence degree of outcrossing. A characterisation of these attributes in relation to cross pollination in wheat may be helpful in assuming the efficiency of hybrid seed production, under given environmental conditions involving specific A and R lines.

A few reports on anther size, pollen production and shedding (KHERDE et al. 1967, JOPPA et al. 1968, BERI and ANAND, 1971) have revealed considerable variation in the outcrossing potential of the different wheat varieties. However, none of the studies involved male fertility restorer lines.

Besides effective restoring ability a good restorer line should be an efficient outcrosser. Pollen producing ability i.e. number of pollen available for outcrossing, anther and filament size, is related with the outcrossing potential of a variety. The present study, reports on production and shedding of pollen in different male fertility restorer lines of wheat and the possibility of using this attribute as an index for selecting R-lines possessing efficient outcrossing devices.

Ten anthers from each of the 10 elite restorer lines, namely, R-995, R-1315, R-1324, R-1326, R-1359, R-1360, R-1362, R-1363, R-1364, obtained from Dr. J.A. Wilson, U.S.A. and R-Dirk received from Dr. L. H. Shebeski, Canada, were measured for their sizes (length x width in mm²). Filament length in mm of the corresponding stamens was also recorded. The measurements were taken with the help of occulomicrometer at X 50 under ordinary microscope.

Number of pollen grains per anther was estimated in anthers which were about to extruse. Such an anther was put on slide in one per-cent acetocarmine solution, cut in three pieces, tapped gently, spread uniformly and each piece was covered with seperate cover slip. All the pollen grains in the three pieces of an anther were counted under microscope. Number of pollen grains available for outcrossing were estimated by counting them in anthers which had just extruded and come out of the floret by applying the same method as described above.

Ten different T. timopheevi restorers were studied for filament length, anther size, total number of pollen grains per anther and number of pollen grains used for outcrossing. Observations on these attributes are presented in Table 1.

Restorer Dirk produced the highest number of pollen grains per anther followed by R-1315, R-1324 and R-1326. Restorer R-1326, despite its lower number of total pollen grains per anther, had the second highest number of pollen grains shed outside the floret which were eventually used for outcorssing. Total number of pollen grains per anther for the 10 different restorer lines studied varied from 975 to 2773 and the pollen grains per anther used for outcrossing ranged from 308 in R-1364 to 1406 in R-Dirk. Filament length varied from 7.0 (R-1359) to 11.9 mm (R-1364) and anther size ranged from 3.2 (R-1364) to 6.8 mm² (R-Dirk and R-1315). The larger anthers were found to possess more number of pollen grains. However, no association was observed between the filament length and percentage of pollen grains used for outcrossing.

(Received August 24, 1974)