Assessing the genetic resources to improve drought tolerance in sugar beet: agronomic traits of diverse genotypes under droughted and irrigated conditions

Drought is the major cause of sugar beet (Beta vulgaris L.) yield losses in the UK and many other regions where the crop is not normally irrigated. However, drought tolerance has not been a breeding target partly because the extent of the problem was not understood, it is difficult to design effective selection screens, and because of the suspicion that few varietal differences existed. The aim of this study was to evaluate the genetic resources necessary to improve drought tolerance. Specific objectives were to assess the degree of genotypic diversity for drought tolerance, characterise genotypic differences in response to drought, and identify sources of germplasm with greater drought tolerance than current commercial varieties. Over 3 years, 46 beet genotypes representing diverse genetic backgrounds were tested in the field under large polythene covers to impose a drought beginning approximately 40 days after emergence until harvest. Sugar, root and total dry matter yields were measured under drought and irrigated conditions. The percentage green crop cover was measured at regular intervals and used in the calculation of radiation use efficiencies for each genotype. Drought tolerance index (DTI) was computed as the fraction of irrigated yield maintained under drought, normalised by the mean yield across all genotypes in the trial. Seven genotypes were tested in all years, and the data on these were used to calculate yield stability statistics and to estimate broad-sense heritability. There were more than two-fold differences in droughted and irrigated yields between genotypes, and nearly a two-fold difference in DTI. According to an index that combines yield potential and drought tolerance, some genotypes performed better than the three locally adapted commercial varieties included in the test. There were significant effects for genotype, treatment and G×E interactions for yield components and radiation use efficiency. There were also significant genotype differences in harvest index but few significant G×E interactions. Droughted and irrigated yields were positively associated, but there was no close relation between yield potential and DTI. The seven genotypes common to all years differed in yield stability and in sensitivity to water availability. Thus, the genetic resources exist for germplasm improvement. Both yield potential and DTI (which may ensure better yield stability) should be considered simultaneously as breeding targets for drought-prone areas.     

Hunting vulnerability, ecological characteristics and harvest rates of bushmeat species in afrotropical forests

We reviewed and analysed patterns and between-site variation in hunter-kill profiles of mammals in tropical moist forests in west and central Africa. Published data from 36 sites in seven countries were used. A total of 71 mammals from 8 orders and 22 families were hunted. Significant variation was found in number of species exploited, but ungulates constituted 73.2% of all hunted animals. Rodents and primates contributed 12.2% and 12.0%, respectively. Large-bodied species (15.0-99.9 kg) represented over half (54.4%) of the total hunted biomass. Most species were snared, and were generally medium-sized, fast, terrestrial, frugivore-herbivores. By species, we showed using meta-analysis, that abundance was the main predictor of harvest level. But, the relationship between hunter presence (calculated as average hunter numbers operating per 100 days) and hunter ease (an index of catchability of the hunted fauna) and site harvest levels was shown to be significant only for hunter ease. Site harvest rates were higher in areas with more hunter presence. Overall, an average of 2000 carcasses (16,000 kg in weight) per site was extracted in a year. Per hunter, this amounted to 200 carcasses (1000 kg) extracted. Such amounts fall within reported unsustainable harvest levels of the mammalian fauna in African forests.     

Comparison of Growth,Pod Distribution and Canopy Structure of Old and New Cultivars of Oilseed Rape ( Brassica napus L.)

Growth, canopy structure and yield components of four selected spring-type cultivars of oilseed rape (Derby, Cyclone, Gulle and Christa) were studied in a field experiment conducted in 1993. Growth analysis was carried out by taking six samples at two-weekly intervals. Area indices of leaves, stems and pods as well as dry matter of plant components were measured. The cultivars showed two different patterns of development and were classified into two groups: old and new cultivars. The first group (Derby and Cyclone) was characterized by short plants, bearing more branches that started branching earlier and on a low position on the stem, while the second group (Gulle and Christa) were characterized by tall plants with thick stems and few branches, starting higher on the stem. Yield could not be directly related to differences in the canopy structure between old and new types. The highest yielding cultivar (Cyclone) belonged to the new category, but the second highest yielding cultivar (Gulle) was of the old type. The study of canopy structure revealed that the pods were distributed evenly on the uppermost branches of the cultivar Cyclone, while for the other cultivars most of the pods were on the main stem, especially in cultivars Gulle and Christa (old group). The cultivars differed significantly in most yield components. In addition to stem and pod development, number of branches and leaf area after anthesis were important characteristics for yield improvement. There were significant differences between cultivars in oil and protein content.     

Influence Of Temperature Shift After Flowering on Dry Matter Partitioning In Two Cultivars of Snap Bean (Phaseolus Vulgaris)That Differ In Heat Tolerance

Abstract

The Partitioning of Dry Matter (Ratio of Dry Weight of Individual Parts To That of Total Dry Matter) Was Analyzed In Snap Bean Cultivars, Haibushi, A Heat-Tolerant Cultivar, and Kentucky Wonder, A Heat-Sensitive Cultivar, At Four Temperatures After Flowering on The Subtropical Island of Ishigaki, Japan. The Temperature Regimes Included 27/23ºC (Day/Night) As Normal, 24/20ºC As Low, 30/26 As High, and 33/29ºC As Extremely High. Most Growth Traits Increased After Flowering Time (35 Das), Displaying A Plateau At 68-75 Das. The Total Dry Matter Was Similar Under All Temperature Conditions, But Differed With The Cultivar. Haibushi Had A Higher Value of Total Dry Matter Than Kentucky Wonder, Which Was Mainly Due To Higher Pod Dry Weight Although Stem and Root Dry Weights Were Lower In Haibushi. A Sharp Decline of Dry Matter Partitioning To Pods Was Observed At 33/29 ºC. In The Temperature Range of 24/20 To 30/26ºC, Haibushi Showed Higher Partitioning To Pods Than Kentucky Wonder, Independent of Temperature. on The Other Contrary, Kentucky Wonder Showed Higher Partitioning To Pods At 27/23ºC Than At 24/20ºC. These Results Showed That The Partitioning of Dry Matter, Which Varied With The Cultivar and Temperature, Played An Important Role In Achieving Higher Harvest Index In The Heat-Tolerant Than In The Heat-Sensitive Cultivars.     

采收时期对鲜食糯玉米品质和产量的影响

以国审郑白糯918糯玉米品种为研究对象,分3个采收时期研究了采收时期不同对糯玉米品质和产量的影响。研究结果表明：采收时期不同,对鲜食糯玉米籽粒主要营养组分含量和微量元素含量影响较大,对鲜穗产量影响较小。粗蛋白含量随着采收时期的推迟含量先下降后上升,总体表现为降低;粗脂肪和粗淀粉含量是随着授粉天数的增加而逐渐增加;赖氨酸含量和可溶性总糖的含量随着采收期的推迟逐渐降低;铁含量随着采收期推迟含量先上升后下降;镁含量随着采收期推迟含量先下降后上升,总体表现为下降;钙含量随着采收期的推迟逐渐降低。     

建平地区烤烟采收环节运输机械的应用研究

[目的]针对建平地区烟叶生产雇工难、雇工贵、用工“野蛮操作”导致烟叶机械损伤严重等问题,对其采收运输机械的研究。[方法]通过合理设计烟田部分垄距增加小型农机进地的可能性,采后烟叶放置于专门的编织袋中,运输工使用改进电动三轮车进烟田运烟,然后用安装有专用运输架的运输车运回烤房进行编烟,编烟后放置于专门挂烟架上,全部编完后装到烤房内。[结果]机械的使用大幅降低了烟叶的机械损伤,显著提高了烟叶等级质量,降低了烟叶采收的劳动强度,大幅缩短了采烟全程时间。[结论]减少人为机械损伤,实现提质增效目标,为烤烟采收环节优化提供参考。     

北疆玉米密植高产宜粒收品种筛选

筛选耐密植、产量潜力大、脱水快、适宜机械粒收的品种是玉米密植高产全程机械化绿色生产的关键。在密植栽培条件下,2012-2017年在北疆昌吉奇台总场、伊犁新源71团和伊宁县3地开展了15个点次、133个品种/组合267个品次的品种/组合筛选试验,收获时采取机械粒收测产方式,测试收获质量、子粒含水率和单产,并按子粒含水率和产量水平2个指标采用双向平均法作图进行品种分类。试验结果表明：（1）267个样本收获时子粒破碎率均值为5.20%,略高于国家标准（GB/T 21961—2008）规定的5%水平;杂质率和产量损失率均值分别为0.67%和0.92%,低于国家标准3%和5%的要求;（2）子粒含水率均值为24.65%,子粒含水率与破碎率呈极显著正相关（r=0.461）,子粒含水率高是造成破碎率高的主要原因,两者关系可以用二次函数y=0.0346x ²-1.443x+18.998（R ²=0.3799,n=267）拟合,当子粒含水率为20.9%时,破碎率最低;（3）筛选出子粒含水率低、单产水平高的品种华美1号、晋单73、金9913、MC670、增玉1317和豫单9953,推荐为玉米密植高产全程机械化绿色生产技术适宜品种;早熟、脱水快、但产量水平低于平均值的品种有KX9384、KWS5383、登海1786、泽玉501和郑单528,推荐在热量资源偏少的地区种植,或作为热量资源适合地区的搭配品种。     

Genotypic variation in grain phosphorus concentration,and opportunities to improve P-use efficiency in rice

Continual removal of phosphorus (P) from fields in rice grains at harvest results in lower soil fertility in low-input farming systems and drives the need for fertiliser inputs in high-input farming systems. High-P content in rice grains (the majority as phytate) contributes little to human nutrition and agronomic practices such as growing seedlings in high-P media or seed P coating at sowing (in direct-sown crops) may overcome the reported need for high-P seed for seedling establishment. Thus, reducing the amount of P in rice grains at maturity through breeding may represent a novel means to reduce ‘mining’ of soil P. We investigated the uptake and partitioning of P in rice plants and examined the scope for breeding rice with lower grain P by assessing genotypic variation for phosphorus harvest index (PHI) and seed P concentrations among a set of 38 rice genotypes in the field. At maturity approximately 75% of total plant P was found in grains and translocation of P from stems and leaves contributed substantially to grain P. However, unlike other cereals such as wheat, rice plants continued dry matter and P accumulation until maturity with approximately 40% of total plant P taken up post anthesis. In the field study, PHI differed significantly among genotypes (from 57 to 87) but was highly correlated to HI (P ≤ 0.001), suggesting that exploiting genotypic variation for this trait may be counterproductive. Grain P concentrations varied from 1.96 to 3.18 mg P g⁻¹, and were neither associated with reductions in grain yield or seed size, nor significantly correlated to HI. Grain P concentration therefore appears to be a suitable screening criterion and the 50% variation observed among genotypes suggests that scope exists for breeding rice with lower grain P concentration to reduce the off-take of P from rice fields at harvest.     

Characterization of sorghum genotypes for traits related to drought tolerance

Grain sorghum (Sorghum bicolor L. Moench) is a genetically diverse cereal crop grown in many semiarid regions of the world. Improving drought tolerance in sorghum is of prime importance. An association panel of about 300 sorghum genotypes from different races, representative of sorghum globally, was assembled for genetic studies. The objectives of this research were to (i) quantify the performance of the association panel under field conditions in Kansas, (ii) characterize the association panel for phenological, physiological and yield traits that might be associated with tolerance to limited moisture (drought), and (iii) identify genotypes with higher yield potential and stability under different environments that may be used in the sorghum breeding program. Results show large diversity for physiological and yield traits such as chlorophyll content, leaf temperature, grain numbers and grain weight per panicle, harvest index and yield. Significant differences were found for plant height, grain weight and numbers per panicle, harvest index, and grain yield among and within races. The US elite lines had the highest number of grains and grain weight per panicle while the guinea and bicolor races recorded the lowest. Harvest index and yield was highest for the US elite lines and the caudatum genotypes. Overall, there was a negative correlation between plant height and grain weight, grain numbers and yield. Harvest index and grain numbers were negatively affected by moisture limitation for all the races. Among the races, the caudatum genotypes were more stable in grain yield across the different environments. Overall, there was a wide variability within the association panel for physiological and yield traits that may prove to be useful for improving drought tolerance in sorghum.     

Influence of agronomic factors on yield and quality of hemp (Cannabis sativa L.) fibre and implication for an innovative production system

Research and development of an innovative production system for hemp (Cannabis sativa L.) fibre for textile use requires the integration of multidisciplinary knowledge from cultivation technique to realization of end products. Research was carried out to study the effect of the agronomic factors cultivation year (2003–2004), genotype (Futura 75 and Tiborszallasi), plant population (120, 240 and 360 plants m⁻²) and harvesting time (beginning and full flowering) on fibre yield and quality in the whole hemp stem, and in the basal and apical stem portions separately. The study of separate stem portions was done to determine the effect on fibre quality of an innovative harvesting and processing system in which hemp stems are cut in two portions of approximately 1 m at harvest to enable processing on modern flax scutching lines.