17. Effect of amylose content on endosperm appearance of hybrid seeds in rice

Ish Kumar and G.S. Khush

International Rice Research Institute, P.O. Box 933, Manila, Philippines

Glutinous rices have none or negligible amounts of amylose content and opaque endosperm appearance. Non glutinous rices may have high (>24%), intermediate (20-24%), low (10-19%) and very low (<10%) amylose content. Varieties with high, intermediate and low amylose content generally have translucent appearance. However, those with very low amylose content have dull or lazy appearance.

In order to study the effect of amylose content on endosperm appearance, we examined the F1 seeds from the crosses of IR29 (a glutinous variety) and IR37307-8 (a very low amylose variety with dull endosperm) with varieties having high, intermediate and low amylose contents (Table 1). The F1 seeds as well as those of parents were harvested, dried, dehulled and milled in Wig- L-Bug. The endosperm appearance was scored phenotypically as opaque, dull, or translucent. Individual grains were analyzed for amylose content. Results were as follows:

Table 1. Endosperm appearance and amylose content in parents and their hybrids.

=============================================================================
Cross             Endosperm appearance*               Amylose content
(P1/P2)                                                 (in percent)
                 ---------------------         -------------------------------
                P1    P1/P2     P2/P1    P2     P1      P1/P2    P2/P1     P2
=============================================================================
IR29/IR37307    O      O         D       O     0.10    1.11     3.06     7.48
IR29/IR3351     O      D         D       T     0.10    5.70     6.10    12.23
IR29/IR24       O      D         T       T     0.10    5.53     12.76   14.88
IR29/IR24632    O      T         T       T     0.10    20.87    22.43   21.90
IR29/BPI121-407 O      T         T       T     0.10    22.92    22.40   24.58
IR29/IR8        O      T         T       T     0.10    23.88    27.54   27.51

IR37307/IR3351  D      D         D       T     7.48    11.20     7.92   12.23
IR37307/IR24    D      D         T       T     7.48     6.86    12.88   14.88
IR37307/IR24632 D      D         T       T     7.48    17.45    16.50   21.90
IR37307/BPI121-407 D   D         T       T     7.48    13.93    18.65   24.58
IR37307/IR8     D      T         T       T     7.48    23.92    26.88   27.51
=============================================================================
*D-dull T-translucent O-opaque

Crosses with IR29
When this glutinous variety was crossed as female with different non-waxy varieties of varying amylose content, the F1 seeds did not have translucent endosperm in all cases as reported earlier. In crosses with low and very low amylose content varieties as pollen parents, the F1 endosperm appearance was dull. However, the endosperm appearance of F1 seeds was translucent, when varieties with intermediate and high amylose contents were used as pollen parents (Table 1). Therefore complete xenia effect was shown only in crosses with varieties of intermediate and high amylose content.

Crosses with IR37307-8
No information is available on the appearance of F1 endosperm when a dull endosperm variety is used as female. In the present study the crosses with low and intermediate amylose varieties as pollen parents, the appearance of F1 endosperm was dull. However, when high amylose variety was used as pollen parent, the resulting F1 seeds had transliucent endosperm.

In rice, like other cereals, the non-waxy pollen has been reported to show xenia effect (Nagai, 1958; Ghos, Chatge and Subramanyan, 1960). This study shows that xenia effect is not a universal phenomenon. The cross of a waxy and a low amylose non-waxy varieties, produced seeds with dull endosperm which could be easily distinguished from translucent as well as opaque endosperm. The results indicate that the potence of a gene to produce xenia effect depends on the amylose content of the pollen parent.

References

Ghosh, R.L. M., M.B. Ghatge and V. Subramanyan, 1960. Rice in India. Indian Council of Agricultural Research, New Delhi.

Nagai, I., 1958. Japonica rice: its breeding and culture. Yokendo, Tokyo, 843 pp.