Simulating Hybrid-seed Contamination Risk with Selfed Seeds from Residual Fertility in a Male-sterile T-4 Mutant Tomato, Solanum lycopersicum L.

Abstract

Environmental dependence of male sterility may sometimes result in residual fertility under 'sterility conditions', causing hybrid-seed contamination risk. An experiment was conducted to assess the risk factor and methods to increase hybrid-seed purity in a thermosensitive male-sterile tomato mutant, T-4, whose fertility is partially restored in autumn, but largely remains sterile in spring, with some residual fertility. Examination of pollen germination and the subsequent pollen-tube growth in vitro and on stigma revealed that a small proportion of the T-4 pollen was viable, with 10-20% germination, while normal pollen from 'Tiny Tim' had 60-85% germination 3-6 h after pollination. A stable male-sterile mutant T-3, whose pollen development collapses at the microspore stage, was pollinated with T-4 pollen followed by normal 'Tiny Tim' pollen with time lags of 2, 4, and 8 h. Concurrently, the T-4 mutant was self-pollinated by hand followed by normal pollen from an inbred line (M) with time lags of 2, 4, 8, 24, and 48 h. The progeny was scored for contamination based on differences in leaf characteristics. The percentage of T-4 seedlings (narrow leaved) in the F 1 progeny was lowest at 2 h (0.2-6.3%), highest at 8 h (16.9-17.7%) and declined at 24 h-48 h (13.5-10.3%) time lag. The contamination rate was extremely low when pollination was done with normal pollen at (0.4%) and 24 h after (1.4%) anthesis without prior hand pollination with T-4 pollen. It was concluded that with pollination timing soon after anthesis, the T-4 mutant could be effectively applied in a two-line hybrid-seed production system with lower roguing cost of undesirable seedlings as opposed to the conventional three-line system.

Assessment of the inheritance pattern of the novel female only flower trait in Jatropha curcas L. as potential for hybrid seed production

“…The pollination for a cross, especially when homozygous inbreds are used, needs to be controlled as this guarantees the desirable combination of inbred traits and avoids pollen contamination on the female inbred parent by selfpollination or with pollen other than that of the desired male contributed by insects (Vaknin et al, 2012), this results in a uniform F1 population offspring, and expresses heterosis for yield (Birchler et al, 2010;Perez-Prat and van Lookeren, 2002). Pollination should be efficient and economical and depends on factors such as the synchronization of the flowering between the female and male parents in an interplanting row plot (Haque et al, 2012) and contamination of the female parent with foreign pollen (Masuda et al, 2010). Some strategies to reduce female pollen contamination include the emasculation by detaselling of the female parent, as in corn (Stevens et al, 2004), the usage of the cytoplasmic male sterility trait (CMS) (Yamagishi and Bhat, 2014) or the transgenic genes based on nuclear-encoded male sterility as the seed production technology (SPT) (Wu et al, 2016).…”