Genetic Diversity and Association Mapping of Grain-Size Traits in Rice Landraces from the Honghe Hani Rice Terraces System in Yunnan Province

The Honghe Hani Rice Terraces System (HHRTS) of Yunnan Province is an important agricultural and cultural heritage landscape. Until now, a large number of local rice landraces have been planted. Mining excellent genes contained in these landraces provides a reference for variety improvement and new variety breeding. In this study, 96 rice landraces collected from the Hani terraces were planted in Honghe Mengzi, Yunnan Province, in 2013, 2014, 2015, and 2021, and five major grain traits were measured and analyzed. The genomic variation of 96 rice landraces was scanned by 201 simple sequence repeat (SSR) markers. The genetic diversity, population structure, and genetic relationships of the natural population were analyzed. The mixed linear model (MLM) method of the TASSEL software was used to analyze the associations between markers and traits. A total of 936 alleles were amplified by 201 pairs of SSR primers. The average number of observed alleles (Na), the effective number of alleles (Ne), Shannon's information index (I), heterozygosity (H), and the polymorphism information content (PIC) per marker were 4.66, 2.71, 1.08, 0.15, and 0.55, respectively. Ninety-six landraces were divided into two groups by population structure, clustering, and principal component analysis, and indica rice was the main group. The coefficients of variation of the five traits ranged from 6.80 to 15.24%, and their broad heritabilities were more than 70%. In addition, there were positive correlations among the same grain traits between different years. Through MLM analysis, 2, 36, 7, 7, and 4 SSR markers were significantly associated with grain length (GL), grain width (GW), grain thickness (GT), grain length-width ratio (LWR), and thousand-grain weight (TGW), respectively. The explanation rates of phenotypic variation were 16.31 (RM449, Chr. 1)-23.51% (RM316, Chr. 9), 10.84 (RM523, Chr. 3; RM161/RM305, Chr. 5)-43.01% (RM5496, Chr. 1), 11.98 (RM161/RM305, Chr. 5)-24.72% (RM275, Chr. 6), 12.68 (RM126, Chr. 8)-36.96% (RM5496, Chr. 1), and 17.65 (RM4499, Chr. 2)-26.32% (RM25, Chr. 8), respectively. The associated markers were distributed on 12 chromosomes of the genome.

Relationship, Discourse and Construction: The Power Process and Environmental Impact of the Honghe Hani Rice Terraces as a World Heritage Site

The coexistence of conservation and degradation is a challenge for protected areas, and unequal political and social power is the mechanism underlying this conservation paradox. The World Heritage site of the Honghe Hani Rice Terraces (HHRT) has important natural and cultural value, but despite the enormous investment in protecting the site, the rice terraces continue to degrade, and much of the degradation has been unexpected. This study attempts to reveal the mechanism of these unintended protection outputs from the perspective of power relations. After reviewing the literature on the political ecology of protected areas, this study further considers the conceptual framework of power in view of the ambiguity of the concept and integrates the themes from research on protected areas into the power analysis framework of political ecology. Three aspects of the power process and environmental impact of heritage sites are analyzed: the actor network, conservation discourse and natural reconstruction. The results reveal that power among actors in the HHRT has changed over the course of continuous interaction, power has been produced and re-established in different relational networks, and the exercise of power has changed and reshaped the natural environment of the heritage site through a series of spatial planning decisions. Conservation discourse related to heritage is an important way for actors to establish and exercise power. However, due to spatial differences in the allocation of power, local development opportunities are unbalanced. In this unbalanced relationship, in order to maintain or strive for development opportunities and achieve economic development, residents of the HHRT have reshaped the natural environment by changing their farming methods and traditional planting methods, posing a potential threat to the sustainable development of the heritage site.