Seed production of two brachiaria hybrid cultivars in - Tropical ...

32 M.D. Hare, P. Tatsapong and K. Saipraset
or other Brachiaria spp. (negligible seed yields)
in earlier trials on the same site (Hare et al. 2005),
but below seed yields of ruzi grass (313–350 kg/
ha) elsewhere in Thailand (Phaikaew and Pholsen
1993; Kowithayakorn and Phaikaew 1993).
Both Mulato and Mulato II produced sufficient
inflorescences, racemes and spikelets to
indicate a potential for useful seed yields. However,
by seed harvest, there was massive failure
of seed-set, caryopsis maturation or both, with
the cleaned seed containing less than 2% of
the spikelets formed by the crops. Weather conditions
during seed maturation were suitable for
seed-set, with bright sunshine and no rain. The
subsequent failure of seed-set most probably was
due to pollen sterility, if judged by a study on
brachiaria hybrids showing that more than 65%
of pollen grains were sterile (Risso-Pascotto et al.
2005) and that this sterility was genetic.
However, in further trials on closing date
(Hare et al. 2007a) and harvesting methods (Hare
et al. 2007b), the highest seed yields of Mulato
II reached 258 and 580 kg/ha, respectively, while
those of Mulato remained low, indicating that not
all brachiaria hybrids have genetically low seed
yields. The low seed yields of Mulato II in this
study (Trial 4) were due to the trial site becoming
severely waterlogged in September, causing
tiller death and a very low emergence of inflorescences.
In contrast, the harvesting method trial
50 m away in the same paddock was not waterlogged
and the best treatment produced seed
yields of 580 kg/ha (Hare et al. 2007b). Smallholder
farmers have also produced Mulato II seed
yields in excess of 500 kg/ha.
The results emphasise the importance of
method of establishment for seed production
in these brachiaria hybrids. In our studies, seed
Table 9. Effect of method and time of planting of Mulato on dry matter yields in stubble at seed harvest (Trial 3).
Method of planting
Stem DM
(kg/ha)
Leaf DM
(kg/ha)
Total DM
(kg/ha)
Seed 5220 3381 8601
Tillers 6212 3693 9905
LSD (P < 0.05) 940 ns 1238
Time of planting
May 5991 3793 9 784
June 6031 3563 9 594
July 6420 3787 10 207
August 4423 3005 7 428
LSD (P < 0.05) 1329 587 1 752
Table 10. Effect of time of planting of Mulato II on dry matter yields and crude protein (CP) concentrations in forage cut at closing
(August) for seed production (Trial 4).
Tiller planting time
Stem DM
(kg/ha)
Stem CP (%)
Leaf DM
(kg/ha)
Leaf CP (%)
Total DM
(kg/ha)
May 16 1433 10.2 1725 13.4 3158
June 1 440 12.0 653 17.6 1093
June 16 123 13.4 312 17.8 434
July 1 46 15.5 165 17.2 211
LSD (P < 0.05) 325 2.0 335 1.8 647
Table 11. Effect of time of planting of Mulato II on dry matter yields in stubble at seed harvest (Trial 4).
Tiller planting time
Stem DM
(kg/ha)
Leaf DM
(kg/ha)
Total DM
(kg/ha)
May 16 5085 4524 9609
June 1 4073 3549 7622
June 16 3568 3681 7249
July 1 2824 3172 5996
July 15 2197 2666 4863
August 1 1475 2152 3627
August 16 595 1357 1952
LSD (P < 0.05) 1402 750 1919