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Rice Genomics and Genetics 2012, Vol.3, No.2, 8
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investigated in 10 days after spraying. The results
showed that the seedlings began to be suffering in the
next day, and after 10 days later, the control's seedlings
of Ganxiang B were dead at all. Three NIL lines derived
from 11 combinations had some surviving seedlings,
of which total of nine individuals were identified to
have some resistance to herbicide.
2 Discussion
In this study, a batch of wild rices come from different
sources of as the donors, elite maintainer Ganxiang
B as the receptor, a large number of crossing and
backcrossing were carried out to build near-isogenic
introgression lines with the genetic background of,
elite maintainer, having achieved a large number of
materials with different phenotypic characteristics of
wild rice. Regarding the large-scale screening process
for rice favorable traits, we considered the effects of
selections were dependent on whether the selection
criteria could extreme match the favorable goals. For
example, Conditions for screening drought tolerance
in rice blooming growth stage must be ensured under
the continuing high temperature and drought, was well
as the control of drought-susceptive material has to
appear leaf curling, wilting, basically not being restored.
Conditions for screening the low-nitrogen tolerant
materials must to be guaranteed to applying no nitrogen
fertilizer that will facilitate to screen low tolerant
materials, otherwise if nitrogen fertilizer were applied
too much there would be very small differences
exhibiting among the lines. Screening high-temperature
tolerant materials must be required under the condition
of a high temperature at 35
℃
or more during the
rice heading stage. It is necessary for screening the
flooding tolerant materials to completely submerged
rice seedlings as well as to ensure that the flooding
condition was maintained even in the process of water
changing, the majority of seedlings died at all. The
screening results also need to be further validated
under the controllable conditions. In this study, we
acquired a batch of potential breeding values and
prospective use of new germplasms though a large scale
screening the favorable traits, such as drought, low
nitrogen, high temperature, blast, flooding, herbicides,
etc.. Using these favorable germplasms could enhance
the characters of Ganxiang B including abilities of
anti-abiotic stresses, capacity of low nitrogen tolerance
and disease resistance, it would be the foundations for
breeding the cultivar of green super rice. Also, in the
view of the screening results for building a large-scale
NILs, we have screened most of the improved target
traits from the NILs derived from the wild rice as
donors, which further indicated that there should be
many favorable target genes in wild rice.
3 Materials and Methods
3.1 Recurrent parent of Ganxiang B as genetic
background
Gangxiang B, an elite maintainer of three-line hybrid
rice developed by Rice Institute of Jiangxi Academy
of Agricultural Sciences, bred by multiple crossing
among five different sources of rice germplsams of
03B, IR58025B, Jing 23B, Xinlu B and Jiangnong B.
The ganxiang B has excellent figures with thickened
stem, strong individual strengths and with 12~13
leaves of main stem. In the mature stage, functional
leaves keep vigorous, no pre-aging, good leaf color
transiting. The plant architecture is moderate tight
with pendulous panicle under the flag leaf, strong
tillering ability, well developed root system, the flag
leaf erecting, large spike with more grains, dense grain
setting and 22 cm of panicle in length, the average
number of 150 grains per panicle, Kilo-seed weight
28~29 g, not easy shattering, 3.3 of ratio of length to
width, aromatic flavor, stigma extruding, high content
of straight chain starch and susceptible to temperature.
F
1
hybrid mating with the genetic background of
Ganxiang B has a strong early maturity but normal
ability to high temperature tolerance.
3.2 Donor parents
Eleven different sources of wild rice germplasms,
named Dongxiang wild rice, Guangxi wild rice,
Jiangyong wild rice, Chaling wild rice, Yuanjiang
common wild rice Hehuatang No 2, 4 and 10. Four
wild rice germplasms namely 06YD2, 06YD5, 06YD6,
and 06YD12 provided by Huazhong Agricultural
University.
3.3 Screening methods for target characters
Screening for drought tolerance: Lines was sown
by backcross combinations in upland of Nanchang.
Seedlings were nursing in wet field, the growing season