Repeatability of different stability parameters for grain yield in chickpea

The presence of genotype × environment (GE) interactions in plant breeding experiments has led to the development of several stability parameters in the past few decades. The present study investigated the repeatability of these parameters for 16 chickpea (Cicer arietinum L.) genotypes by correlating their estimates obtained from extreme subsets of environments within a year and also over years. Based on the estimates of response and stability parameters within each trial, the ranking of genotypes in the low-yielding subset differed from that in the high-yielding subset. This indicates poor repeatability for response and stability parameters over the extreme environmental subsets. The estimates of mean yield and stability parameters represented by ecovalence, W²_i, were consistent over years, whereas those of response parameters (b_i, and S²_i) showed poor repeatability. Our results suggest that single-year results for yield and stability can be used effectively for selecting cultivars with stable grain yield if tested in a wider range of environments.     

四川省西北地区沙化土地驱动机制研究

采用文献收集法,结合川西北实际情况,筛选出典型自然和人为因子,分析因子变化趋势及与沙化面积变化相关性。采用主成分分析法,研究了川西土地沙化的驱动机制。结果表明,近60年来,川西北年平均气温、年大风日数呈显著上升趋势,和沙化面积变化显著正相关（P=0.000）;年降水量波动较大但总体保持平稳,其相关性不显著;年平均风速有明显减小趋势,和沙化面积变化显著负相关（P=0.014）;总人口、畜牧产值、大牲畜存栏数、牛羊肉产量等人为因子均明显增长,且和沙化面积显著正相关（P≤0.009）;分析认为,川西北土地沙化是自然和人为因子综合作用的结果,总人口、牧业产值、大牲畜存栏数、年平均风速、年平均温度组成的第1主成分是川西北土地沙化的主要驱动力,其贡献率为59.174%。     

Reviews

Books reviewed: Ben Burt and Christian Clerk (eds), Environment and development in the Pacific Islands Glenn Banks and Chris Ballard (eds), The Oki Tedi Settlement – issues, outcomes and implications Bill Gammage, The Sky Travellers: journeys in New Guinea 1938–1939     

Heterosis in inter and intrasubspecific crosses over three-environments in rice

Moderate to high heterosis for yield and ten related characters was studied in 45 crosses involving six indica (I) and four tropical japonica (J) varieties of rice under three (E₁-optimum sowing and high fertility, E₂-both optimum sowing and fertility and E₃- late sowing and high fertility) environments. Trends of magnitude of heterosis for grain yield and plant height were I/J > I/I > J/J and for days to 50% flowering I/J > J/J > I/I hybrids. Estimates of standard heterosis (%) for grain yield were –64.5 to 146.1 in E₁, –70.4 to 82.2 in E₂ and –67.2 to 63.8 in E₃. Environment E₁ seemed to be more favorable for higher heterosis expression than others. Higher heterosis in yield also accompanied heterosis in panicle number, dry matter and spikelet and grain number per panicle. Most estimates for days to flower were negative. Heterotic I/J hybrids also recorded maximum heterosis for earliness. Moderate to low standard heterosis for plant height across environments (2.0 to 13.7%) was recorded. Hybrids were identified in specific environments for direct exploitation in hybrid breeding. Hybrids B4116 / Sarjoo 52, B4122 / Pant Dhan 4 and B4122 / Narendera 359 were more stable than others over three environments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Land tenure and farm management efficiency: The case of smallholder rubber production in customary land areas of Sumatra

This study assesses the impact of land tenure institutions on the efficiency of farm management based on a case study of rubber production in customary land areas of Sumatra, Indonesia. Using the modes of land acquisition as measures of land tenure institutions, we estimated tree planting, revenue, income, and short-run profit functions, and internal rates of return to tree planting on smallholder rubber fields. We find generally insignificant differences in the incidence of tree planting and management efficiency (defined as residual profits) of rubber production between newly emerging private ownership and customary ownership. This is consistent with our hypothesis that tree planting confers stronger individual rights, if land rights are initially weak (as in the case of family land under customary land tenure systems). On the other hand, short-term profits are higher on land that is rented through share tenancy. This result indicates that rubber trees are over-exploited under renting arrangements due partly to the short-run nature of the land tenancy contracts and partly to the difficulty landowners face in supervising tapping activities of tenants in spatially dispersed rubber fields. This revised version was published online in June 2006 with corrections to the Cover Date.