• Rgn12

    0. barthii A. Chev. (designated by Clayton 1968: usually called O. breviligulata A. Chev. et Roehr.) is an annual wild-rice species distributed in West Africa and is thought to be the wild progenitor of 0. glaberrima. Its 11 strains were collected mainly from Bauchi State. Nigeria. They were studied in this work. The strains include long-grained (TOB 8218 & Kari 83), with embryo non-dormant (TOB 8218 & TOB 7307), photoperiod insensitive (TOB8218, TOB 8226, TOB 5646, TOB 5660, TOB 7311, TOB 7382 & TOB 7307). and photoperiod sensitive (TOB 7337. Kari 83. TOB 10838 & TOB 5645) accessions. Mean character values and standard deviations obtained in each accession are summarized in Table 1: cf. Fig. 1.

    These plants are found abundantly in some localities, and are harvested by the people as food. We have studied them to clarify their potential as genetic resources, with the veiw to improve themselves and utilize them for improvement of cultivated rice.

    Reciprocal crosses were made between TOB 5646 (awned. hulls black, with open panicles) and TOB 8218 (awnless, hulls straw-color, with compact panicles), and the F₂ seeds were examined. Hulled and dehulled seeds were germinated in petri-dishes. Embryo dormancy (ED) was assessed by the germination of dehulled seeds in 12days. Hull-imposed dormancy (HID: Shenoy 1993) was assessed by the germination of hulled seeds in 36 days. Panicle parameters were measured also in the F₂.

    Percent awn weight (awn/spikelet) ranged between 3.6% in TOB 7382 and 10.2% in Kari 83. indicating that awn is a substantial part of biological production (Table 1 ). In the

Fig. 1. Panicles of F₂ plants from TOB 8218 X TOB 5646. with long
        awns and nearly awnless.

    The F₂ from TOB 8218 (straw-colored hulls) x TOB 5646 (black hulls) segregated
into 123 black hulled and 84 straw-color hulled plants. This fitted a 9:7 ratio, and
suggested that hull coloration is controlled by a set of two complementary genes.
The full coloration had no direct effect on caryopsis coloration. It takes place in the
spikelet at late maturity. Sterile spikelets are not colored black. The number of spikelets per
panicle or prolificacy is a component determining panicle form.

    The components of biological yield as shown by caryopsis weight, awn weight, hull
weight and spikelet weight were measured with the spikelet of F₂ plants dried at 50-54°C

Table 2. Mean. standard deviation, minimum and maximum measurement
        of spikelet weight and other values for awned and awnless strains (in mg)
 

*.** significant at 5% and 1% levels, respectively.

ns non-significant.

for 5 days (Chang 1976). The results are presented in Table 2. The awned and awnless plants did not differ in caryopsis weight significantly.

    Caryopsis weight, hull weight, spikelet weight and awn weight were correlated significantly in most combinations (Table 3). The correlation between caryopsis weight and hull weight may be explained on the basis that the hull provides an aggregate photosynthetic surface for assimilation and the assimilate is partitioned into the caryopsis.

References

Chang, T. T., 1976. Manual on genetic conservation of rice germplasm for evaluation and utilization. IRRI.
            Manila.
Clayton, W. D., 1968. Studies in Gramineae, 17. West African wild rice. Kew Bulletin 21: 485-488.
Jones, J. W., 1927. Inheritance of awnedness in rice. J. Amer. Soc. Agronomy 19: 830-839.
Jones, J. W., 1933. Inheritance of characters in rice. J. Agric. Res. 47: 771-782.
Shenoy. V. V.. 1993. Genetics of hull-imposed dormancy in rice seeds. RGN 10: 108-109.

        Acknowledgments: We thank Mr. Sola Ajayi of Plant Science Department of our University for assistance
in computer analysis.
 
 

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