GENETIC-VARIATION FOR IN-VITRO SESAME POLLEN GERMINATION AND TUBE GROWTH

In vitro pollen germination and tube length studies are valuable in el ucidating mechanisms (germination capacity and rate, tube growth rate) possibly associated with genetic differences in male transmission. On each of two collection dates, the percentage germination and tube len gth of the binucleate pollen grains from live diverse sesame (Sesamum indicum L.) genotypes were determined at eight times (30, 60, 90, 120, 150, 180, 240, 300 min) after inoculation on a semisolid medium conta ining 10% (100 g l(-1)) sucrose (C12H22O11), 0.4% (4 gl(-1)) purified agar (Fisher Lot 914409), 0.1% (1 gl(-1)) calcium nitrate [Ca(NO3)(2) . 4H(2)O] and 0.01% (100 mg l(-1)) boric acid (H3BO3). Before heating, the pH of the medium was adjusted to 7.0 with a 0.1 N potassium hydro xide (KOH) solution. Over the five genotypes, 5% germination was found 30 min after inoculation and a maximum of 37% germination 120 min aft er inoculation with no significant changes thereafter. As indicated by the highly significant genotype x time after inoculation interaction, the genotypes differed in the time at which germination was initiated and maximum germination attained. Over all five genotypes, the tube l ength was 91 mu m 30 min after inoculation, reaching a maximum of 1000 mu m 300 min after inoculation. As shown by the highly significant ge notype x time after inoculation interaction, the genotypes differed in the time at which tube length was observed and the maximum tube lengt h was attained. Little or no relationship between percent germination and tube length was observed among the genotypes. For both percent ger mination and tube length, the statistical significance of collection d ate and its interactions with genotype and time after inoculation indi cated that environment in the form of collection date was also an infl uencing factor. These results indicated that genetic differences among genotypes were present for in vitro germination capacity, germination rate and tube growth rate and that these factors singly or in combina tion could alter male transmission of genetic elements.