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The production of transgenic roots was scored for eight Brassica oleracea cultivars from broccoli, cabbage, cauliflower and kale following inoculation with an Agrobacterium rhizogenes cell line carrying a binary plasmid bearing the green fluorescence protein (gfp) gene in the T-DNA. Significant differences in the numbers of explants producing transgenic roots were observed between cultivars, ranging from 1.4% for Marathon F1 to 57.8% for the Green Duke F1. Three F1 cultivars were subjected to anther culture, and doubled-haploid (DH) lines were used for transformation. The DH lines produced showed considerable variation for transgenic root production with some lines showing increased efficiency compared to the parental F1 cultivar. Grouping of the DH lines into response classes with respect to transgenic root production allowed the development of potential genetic models to explain the variation in performance released from each F1 cultivar. No apparent segregation distortion for transgenic root production was observed in the DH lines following anther culture.

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Both gibberellic acid (GA,) and fluridone, a non-specific inhibitor of ABA biosynthesis, promoted embryo production in anther cultures of Brussels sprouts cv. Hal, but not in cv. Gower. Abscisic acid (ABA) and the gibberellin-biosynthesis inhibitor paclobutrazol inhibited embryo production in both cultivars.

A study was made of the effect of high temperature on the growth response of Brussels sprout filaments to ethylene . Filaments with or without the anthers attached were incubated continuously at 25 °C or 35 °C for 7 days or for 2 days at 35'C followed by 5 days at 25'C . Growth was reduced during both 35'C treatments compared to that of filaments at continuous 25 °C . Ethylene had little effect on filament growth at continuous 25 °C, whereas with treatment for either 2 or 7 days at 35 °C ethylene promoted filament growth considerably . Thus ethylene effectively overcame the growth inhibition induced by the 35'C treatment .High temperature treatments reduced ethylene production from filaments alone, and from filaments with anthers attached . The ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG) and the ethylene action inhibitor AgNO 3 enhanced filament growth at 25 °C but had little or no effect at 35 °C . The relevance of temperature to ethylene sensitivity is discussed in relation to filament growth and to other plant processes in general . 1 . IntroductionEthylene synthesis by plants is very sensitive to changes in temperature [7] and at high temperatures may be greatly reduced [4,6,16] . It has recently been shown with tomato fruit that high temperature may also reduce its effectiveness, making the ripening response less sensitive to ethylene as well as inhibiting its biosynthesis [15] . Because ethylene is implicated in the control of many plant processes [1] it is important to know if high temperature influences ethylene effects in other areas of growth and development . In the present experiments filament growth, which may be affected both positively [10] or negatively [8] by ethylene, was used to test the effects of high temperature on growth responses to ethylene . Brussels sprout filaments were chosen because of the possible relevance of the results to Brassica oleracea anther culture, a process which requires a period of high temperature for success and which appears to be inhibited by endogenous ethylene [3,4,5,13] . In the event, high temperature (35°C) led to a promotion of filament growth by ethylene, a result that would seem to have implications not only for understanding the control of filament growth, but also for ethylene physiology in general . . Materials and methodsThe methods and conditions for raising Brussels sprout (Brassica oleracea var . gemmifera, cv . Hal) donor plants were similar to those described previously for anther culture [5] . Following vernalisation plants were allowed to flower in a growth room under 40W white flourescent tubes (28 W m_ 2 ) set to give 16h days with day and night temperature both at approximately 13 °C .

Abscisic acid (ABA) inhibited embryogenesis in anther culture of Brussels sprouts. This was accompanied by enhanced ethylene production during the first half of the anther culture period followed by a reduction in ethylene during the latter half, when compared to anthers not treated with ABA. The enhancement of ethylene production by ABA 6 h and 48 h after the start of the culture period was counteracted by the ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG). Both AVG and the ethylene antagonist AgNO removed much of the ABA inhibition of embryogenesis, suggesting that at least part of the ABA effect on embryo production is mediated through increased ethylene biosynthesis. ABA promotion of ethylene production was reduced by high temperature: less ethylene evolved from ABA-treated anthers following a 24 h treatment at 35°C than from ABA-treated anthers incubated continuously at 25°C. A high temperature treatment such as this is invariably necessary for embryogenesis in Brussels sprouts anther culture.