Yields and Agronomic Characters of New Rice Hybrids Performed at Pine Bluff , Arkansas

Yields and agronomic characters of 35 new hybrids were tested at Pine Bluff, Arkansas in 2013. These hybrids were developed from 7 female parent sterile lines, UP-1s, UP-3s, 100s, 101s, 105s, 111s, and 113A, and 5 male parent restorer lines, PB2, PB5, PB12, PB13, and PB18. The inbred variety Francis, which is a popular variety in the rice production, was used as the check (CK). Results showed that the yields of 10 hybrids were 20.3% 31.7% higher than that of CKFrancis. The yields of other 18 hybrids were 10.1% 19.4% higher than CK, and the yields of rest of the hybrids were 2.5% 9.2% higher than CK. Hybrid UP-3s/PB5 had the highest yield, 12,983.8 kg/hectare and over check by 31.7%. The yield of hybrid UP-3s/PB18 and 115A/PB18 were 12,333.7 kg/hectare and over check 25%. The yields of hybrid UP-1s/PB12 was 12,324.6 kg//hectare and over check 24.9%. The sterile lines UP-3s, 113A, 105s, and 101s have good combinability and the average grain yields of their hybrids were over CKby 21.5%, 20.34%, 17.2% and 16.2%, respectively. The restorer lines PB18, PB5, and PB12 have good combinability and the average grain yields of their hybrids were over CKby 19.9%, 18.4% and 16.2%, respectively. These results indicated that these top hybrids and their parents of the sterile lines and restorer lines might be used in the hybrid rice breeding and production in the future.


Introduction
Due to the increasing demand of rice with the rapidly increased in population, more and more rice have to be produced on less land and with less inputs.Hy-brid rice is more profitable, and more sustainable for yield production, therefore utilization of hybrid rice is an important technology to meet the increasing rice demand in world [1].
Hybrid rice is the commercial rice crop grown from F1 seeds of a cross between two genetically dissimilar parents, and have the potential of yielding 15% -20% more than the best inbred variety grown under similar conditions [2].Hybrids also have shown an ability to perform better under adverse conditions of drought and salinity [3].China started hybrid rice research in 1964 and began large scale hybrid rice commercialization in 1976.
The research of hybrid rice began in USA in 1980s and released first hybrid rice in 2000 from the Rice Tec company [4].Hybrid rice has been widely grown in the US now.It had covered about 40% -60% of the rice acreage in Texas during 2014 to 2016 [5] [6].It had covered about 40% of the rice acreage in Arkansas during 2013 to 2016 [7].Also it had covered about 25% -27.4% of the rice acreage in Louisiana during 2013 to 2016 [8].However, the price of hybrid seeds is kind of expensive currently.The farmers need more diversity and affordable hybrids in their rice production to make more profit.Therefore, hybrid rice research is very important for the objective.
Different germplasms from USDA (United States Department of Agriculture) world rice collection have been utilized and accessed in the hybrid breeding.Some new sterile lines, maintain lines, restorer lines and hybrids have been screened and bred from them.The identifying and evaluating activities have generated a lot of knowledge of hybrid breeding, selected resistant varieties and developed some hybrids from the public research program [9] [10] [11].Hundreds new hybrids were made and identified from this research team in Arkansas.Some of those new hybrid varieties performed very well at Beaumont, Texas in past two years where is more south from Arkansas.
The 35 new hybrids from those sterile and restore parents and the check inbred Francis were tested for agronomic traits and yield at Pine bluff, AR in 2013.
The test entries were sowed at spring 2013 in the greenhouse and transplanted to field with 20 days old seedlings (about four-leaf stage) at 6 inch per plant and 1 ft row space.
The herbicide Command (1 pint/acre) and Permit (1 oz/acre) applied in the pre-emergent herbicides condition on April 24.
Nitrogen fertilizer was applied 200 kg N/ha.The flood was maintained throughout the growing season.Heading dates were recorded when 50% of the plants were headed.Panicles of each plot with 1.52 meter × 2.43 meter = (3.6916m 2 /plot) were harvested about 40 days after heading.Plant heights were measured before harvest.Yield, milled rice, and head rice also were measured.
Daily maximum temperatures (Table 2) were recorded by the sensor of NRCS Arkansas scan sites which is 50 meters away from field of study [12].Average Yields and stand error of the mean were analyzed by SAS 9.2.

Results
1) The grain yield of new hybrid rice a) Specific hybrids The results showed that all the yields of hybrids are higher than check Francis (Table 3).The yields of top 10 hybrid rice were 20.3% -31.7% higher than that of check Francis; yields of middle 18 hybrids were 10.1% -19.4% higher than that of check Francis; and yields of last 7 hybrids were 2.6% -9.2% over than that of check Francis (Table 3).
The top 10 hybrids as follows: The hybrid UP-3s/PB5 yielded 12,983.8kg/hectare and 31.7% higher than check Francis.
The hybrid UP-1s/PB12 yielded 12,324.6 kg/hectare and 24.9% higher than check Francis.The hybrid 105s/PB18 got grain yield 12,297.5 kg/hectare and 24.6% higher than check Francis.
The hybrid 105s/PB5 and 113A/PB13 yielded 11,873.2kg/hectare and 20.3% higher than check Francis.b) Average yields of same sterile lines crossing 6 restorer lines and a same restorer line crossing 6 sterile lines.
Table 4 (horizontally) listed the average yields of hybrids from the same sterile line crossed with 5 different restorer lines, PB2, PB5, PB12, PB13 andPB18: i) Hybrids developed from sterile line UP-3s had the highest average yield of 11,990.5 kg/hectare and over CK by 21.5%.
ii) Hybrids developed from sterile line 113A had the second high average yield of 11,878.5 kg/hectare and over CK by 20.34%.2) The heading days from planting to heading All the heading days of the hybrids from planting to heading were longer than CK Francis, excepting hybrid UP-3s/ PB13 was the same 75.7 days as CK Francis (Table 5).The heading days of the rest 34 hybrids were 76 days -94.3 days 3. Thirty-five hybrids were made from 7 sterile line Up-1s, UP-3s,

Table 1 .
Pedigree of the of the parents of the Thirty-five hybrids.

Table 2 .
Daily maximum air temperature (˚C) in the UAPB field from June to October 2013.

Table 3 .
The grain yield of new hybrids at Pine Bluff, Arkansas 2013.

Table 4 .
Average hybrid yields from one parent line crossing other relevant and different parent lines.

Table 5 .
Heading dates and plant heights of new hybrids at Pine Bluff, AR 2013.