Contribution of ear photosynthesis to grain yield under rainfed and irrigation conditions for winter wheat cultivars released in the past 30 years in North China Plain

To understand the contribution of ear photosynthesis to grain yield and its response to water supply in the improvement of winter wheat, 15 cultivars released from 1980 to 2012 in North China Plain（NCP） were planted under rainfed and irrigated conditions from 2011 to 2013, and the ear photosynthesis was tested by ear shading. During the past 30 years, grain yield significantly increased, the flag leaf area slightly increased under irrigated condition but decreased significantly under rainfed condition, the ratio of grain weight：leaf area significantly increased, and the contribution of ear photosynthesis to grain yield changed from 33.6 to 64.5% and from 32.2 to 57.2% under rainfed and irrigated conditions, respectively. Grain yield, yield components, and ratio of grain weight：leaf area were positively related with contribution of ear photosynthesis. The increase in grain yield in winter wheat was related with improvement in ear photosynthesis contribution in NCP, especially under rainfed condition.

Historical trends in maize morphology from the 1950s to the 2010s in China

The morphology of the plant and ear is a preliminary selection characteristic in breeding new varieties of maize.As new maize cultivars were developed from the 1950s through the 2010s in China,most had changes in both plant and ear morphological characteristics that contributed substantially to maize yield gains.Over the seven decades,plant and ear height fluctuated with a small increase from the 1950s to 2000s,and then a decrease in the 2010s,while the ear ratio and internodes length below the ear decreased significantly.Leaf angles became significantly more upright,especially for the leaves above the ear,and the leaf area per plant improved markedly.Leaf orientation increased from the 1950s to the 2000s then decreased in the 2010s.Tassel size and the anthesis-silking interval were both reduced substantially.Ear diameter,kernel number,and kernel weight increased from the 1950 to the 2000s,then decreased in the 2010s under the same cultivation conditions.We found that modern maize hybrids have a lower plant height,ear height and ear ratio which increased lodging resistance,a more erect leaf which increased high-density planting tolerance,and smaller ears and kernels which facilitated rapid dehydration during late grain filling.These morphological selection criteria,which are suitable for mechanized operations,are proposed as the focus for future maize breeding.

A genetic diversity assessment of starch quality traits in rice landraces from the Taihu basin,China

There are nearly 1 000 rice landrace varieties in the Taihu basin, China. To assess the genetic diversity of the rice, 24 intragenic molecular markers（representing 17 starch synthesis-related genes） were investigated in 115 Taihu basin rice landraces and 87 improved cultivars simultaneously. The results show that the average genetic diversity and polymorphism information content values of the landraces were higher than those of improved cultivars. In total, 41 and 39 allele combinations（of the 17 genes） were derived from the landraces and improved cultivars, respectively; only two identical allele combinations were found bet ween the two rice variety sources. Cluster analysis, based on the molecular markers, revealed that the rice varieties could be subdivided into five groups and, within these, the japonica improved rice and japonica landrace rice varieties were in two separate groups. According to the quality reference criteria to classify the rice into grades, some of the landraces were found to perform we ll, in terms of starch quality. For example, according to NY /T595-2002 criteria from the Ministry of Agriculture of China, 25 and 33 landraces reached grade 1, in terms of their apparent amylose content and gel consistency. Th e varieties that had outstanding quality could be used as breeding materials for rice quality breeding programs in the future. Our study is useful for future applications, such as genetic diversity studies, the protection of rice variety and improvment of rice quality in breeding programs.

Trends of seasonal forage yield changes of triticale in the southern Great Plains of the United States

Background:The focus of triticale breeding in the southern Great Plains of the United States has been to increase forage yield for autumn-winter seasons when most other forage species are dormant.This study aims to estimate the trends of seasonal yield changes over time.Methods:Yield trials had been conducted in a randomized complete block design for up to two decades.Seasonal yield changes over time were estimated using linear regression analysis.Results:The analysis revealed a significant positive relation between autumn forage yield(relative to common checks)and calendar years when the trials were conducted.The estimated improvement of autumn forage yield was about 1.9%per year on medium and heavy soil at Ardmore,Oklahoma,and about 5.4%per year on light soil at Burneyville,Oklahoma.However,winter forage yield change was minimal and the spring forage yield increase was negative,although this decline was not significant.Total forage yield improvements were about 0.6%and 0.7%per year at Ardmore and Burneyville,respectively.Similar results were also observed when years of cultivars'introduction were used instead.Conclusions:The results indicate a significant gain in autumn forage yield,but a minor gain in the total forage yield due to the yield tradeoff between the autumn and spring seasons.