Variation for ABA concentration in tassels from H99xFR16 and H99xPa91
--Wassom, JJ, Mei, C, Rocheford, TR, Widholm, JM
F2-derived F4 families were developed as a part of a continuing anther culture project in this lab. There is a great deal of variation for responsiveness of maize anthers as explants for tissue culture and we have been investigating genetic and physiological factors significant to this variation. Much of our work has utilized various genotypes originating from crosses of H99, Pa91, and FR16. Previous studies in our lab have indicated genetic variation at the gametophyte and sporophyte level associated with F1 and F2 plants from crosses of these inbreds (Wan, Rocheford, and Widholm, TAG 85:360-365, 1992; Beaumont, Rocheford, and Widholm, Genome 38:968-975, 1995). Therefore, F2-derived F4 families were developed to continue the anther culture studies.
In 1995 the F4 families were grown in a nursery at Urbana, IL. There was one row for each family and approximately 20 plants in each row. The nursery was irrigated when needed. Tassels were harvested for anther culture when microspores were at the late uninucleate to early binucleate stage. Tassels were then cold-treated for 14 d at 8 C in preparation for anther culture. At this time unused parts of the tassels were frozen and stored at -70 C for several weeks before lyophilizing the tassels and assaying florets of the tassels for ABA concentration. Leaf ABA was also measured. Leaf samples from three plants of each family were bulked. There was only one replicate of each family for leaf ABA. The ABA was measured by radioimmunoassay by the method of Quarrie et al. (Planta 173:330-339, 1988).
There was significant variation for ABA concentration in tassels of the tested F4 families (P<0.01). Mean concentrations of ABA ranged from 140 to 1201 ng/g dry weight, with continuous variation between the extremes (Table 1). Leaf ABA concentration ranged from 16 to 108 ng/g fresh weight. Leaf samples were not replicated, so it is not known whether there was significant variation among families. When about half the tassels had been assayed for ABA, a correlation analysis was performed which showed essentially no correlation of ABA concentration in whole florets or leaves with production of embryoids by cultured anthers. Tassel ABA was not correlated with leaf ABA. At this point the ABA assays were discontinued. Nevertheless, it is apparent that these families differ significantly for ABA. Parental inbreds were not assayed.
We wish to acknowledge the performance of ABA assays by David Driver and the use of the lab facilities of Dr. Marty Sachs (Univ. of Ill.). The ABA antibody was provided by S. A. Quarrie.
Table 1. Tassel ABA concentrations of F4 families.
|LSD grouping*||ABA, ng/g dry wt||N||F4 family||Pedigree|
|B C D||672.0||6||PF21a||Pa91xFR16|
|B C D||671.7||3||PF16a||Pa91xFR16|
|GFEJ I H||320.7||9||PF10||Pa91xFR16|
|GFEJ I H||317.0||3||HP77-20||H99xPa91|
|GFEJ I H||313.0||4||PF32a||Pa91xFR16|
|GFEJ I H||312.5||2||PF6a||Pa91xFR16|
|GFEJ I H||310.0||1||HP32b||H99xPa91|
|GFEJ I H||300.0||2||HP6a||H99xPa91|
|GFEJ I H||290.5||2||PF37||Pa91xFR16|
|GF J I H||277.0||1||HP43a||H99xPa91|
|GF J I H||268.5||2||HP35||H99xPa91|
|GF J I H||268.0||5||PF56||Pa91xFR16|
|GF J I H||262.0||1||HP7||H99xPa91|
|GF J I H||253.5||2||PF40a||Pa91xFR16|
|GF J I H||245.0||1||PF35||Pa91xFR16|
|G J I H||233.0||2||HP32a||H99xPa91|
|J I H||206.0||1||HP3a||H99xPa91|
*Means with the same letter are not significantly different according
to LSD (P=0.05).
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