Propagule Quantity and Quality in Traditional Makushi Farming of Cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis>): A Case Study for Understanding Domestication and Evolution of Vegetatively Propagated Crops

Modeling how crop plants evolve under domestication requires estimating among-plant variation in important parameters of the reproductive system, including fecundity – the number of propagules produced – and propagule quality. Measuring these traits poses particular problems in vegetatively propagated crop plants. Unlike seeds, vegetative propagules are not intrinsic biological entities but are prepared by farmers. Propagule number and quality are thus determined by the interaction between plant traits and how farmers prepare propagules. We conducted observations, interviews and experiments to study this interaction in cassava grown by Makushi Amerindians, examining how both sources of variation, in plant traits and in farmers’ practices, combine to determine the number and quality of propagules produced. Increased stake mass, determined mostly by stem diameter, leads to increased yield and also to increased asexual ‘fecundity’ of the resulting plant. Farmers’ practices reflect knowledge of this relationship. Diameter is the key criterion in the selection of stems for stakes. Larger diameters are preferred; when thinner stems are used, stakes are cut longer, partially compensating for reduced mass. These results suggest that conscious and unconscious selection to increase ‘fecundity’ and propagule quality in cassava would act to favor plants with thicker stems. Mean stem diameter is greater, and variation in stem diameter is lower, in little-branched plants. Selection for increased asexual ‘fecundity’ can thus have led to reduction in the degree of branching, one of the most striking differences between domesticated cassava and its wild ancestors. Measuring variation in asexual fecundity is a key step in analyzing evolution of the mixed clonal/sexual reproductive systems that characterize many vegetatively propagated crop plants.     

Reproductive Biology in Wild and Silvicultural Managed Populations of Escontria chiotilla (Cactaceae) in the Tehuacán Valley, Central Mexico

Reproductive biology of the columnar cactus Escontria chiotilla was analysed in wild and silvicultural managed populations in the Tehuacán Valley, Central Mexico, where this cactus is under domestication because of its edible fruits. Anthesis is diurnal, flowers opening between 8:00 and 17:00 h, the period between 12:00 and 13:00 appearing to be crucial in pollination success since at this time the maximum opening of flowers, turgidity of stigma, and activity of flower visitors, as well as the highest nectar production and pollen release occur. The bees Apis mellifera, Bombus pensylvanicus and Xylocopa mexicanorum, and the hummingbirds Amazilia violiceps, Cynanthus sordidus and Cynanthus latirostris were the most frequent flower visitors during the crucial period, and were observed contacting both stamens and stigma of E. chiotilla. No differences were found in anthesis nor in flower visitors among both population types. Distances separating the populations studied and bridges of individuals of E. chiotilla between them are within the radius that bees and hummingbirds may travel, indicating that spatial barrier to pollen flow are unlikely. Breeding system is self-incompatible. Production of flowers occurs during the whole year in both population types, allowing continual pollen flow among them. This observation confirms reports of high gene flow among the populations studied in previous population genetics studies. The high pollen flow among wild and managed population explains that however the occurrence of artificial selection, the process of domestication is in incipient stages presumably because gene flow counteracts effects of artificial selection.     

Diversification of Multipurpose Plant, <Emphasis Type="Italic">Perilla Frutescens</Emphasis>

The traditional Asian crop, Perilla frutescens has multiple uses. There are specialized cultivars for seed oil and for medicinal use, as well as wild/weedy forms growing in various habitats. Based on selective characteristics of leaf odor, anthocyanin pigmentation, seed hardness and seed diameter, the diversity of this species was investigated to clarify the intraspecific differentiation. P. frutescens was divided into five groups by the combination of three qualitative characteristics: leaf odor, anthocyanin pigmentation and seed hardness. Most of the plants cultivated for oil belonged to one group, while medicinal plants belonged to three other groups. Wild/weedy forms were in the last group. The five groups could not be distinguished by seed diameter. Though the plants cultivated for oil tended to have larger seeds than the medicinal and wild/weedy plants, there was no boundary either between the two crops, or among various phenotypes of P. frutescens.     

高粱的起源、驯化与传播

关于高粱的起源、驯化和传播,中外学者提出了多种猜想。最早有印度起源说,再有非洲起源说,中国高粱中国起源说,以及多元起源说等。本文从高粱历史遗存的考古发现、古籍记载、分子生物学研究结果等方面论述了栽培高粱的起源、驯化和传播。认为高粱起源于苏丹热带草原,距今8 000～6 000 a前开始驯化栽培,并向非洲大陆、印度、中东、西亚等周边传播,距今5 000年前传播到印度,4 000～3 000 a前传播到中国西南的云、贵地区。由于远古时期就开始传播,受不同地域气候条件、栽培条件等的影响,原始高粱的形态学性状和生理特性在不同的区域产生了不同的变异,形成了现今五大高粱栽培种之间的差异。中国高粱非中国起源,但中国无疑是高粱的重要驯化中心之一。     

山羊的起源驯化和品种形成

回顾了山羊野祖及其驯化传播过程的传统观点。以考古学、历史学和畜牧学研究结果为依据，提出了家养山羊多地起源的观点，并认为中国是山羊早期独立驯化地之一。认为各地方山羊品种形成是在自然选择和人工选择作用下长期适应的结果，中国北方地区山羊品种形成过程中包含了古代西域山羊的血统。     

中国粳稻起源的探讨

 从多学科角度探讨了中国粳稻的起源。认为我国的粳稻独立起源于偏粳的普通野生稻，籼、粳稻是平行演化的；我国粳稻量重要的起源地是在长江中下游的平原沼泽地带，其中心区域位于太湖流域。     

野生半滑舌鳎的驯养技术

摘要野生半滑舌鳎必须经过驯养后才能做为人工养殖亲鱼使用。试验结果表明，定置网捕获的半滑舌鳎比拖网捕获的成活率高，专门驯养比虾池粗养成活率高。获取野生鱼时的水温与驯养成活率关系密切，5、6、7月份，水温12～22℃时．驯养成活率为50％；8、9月份，水温高于22℃时，驯养成活率为0；11月份水温17．2～12．4℃时，成活率62．9％；12．4～7℃时，成活率36．8％。2003年5月22日～12月5日，共获取野生鱼165尾，驯养成活68尾，成活率41．2％。野生雌鱼随性腺发育程度的增加其驯养难度加大。野生鱼开口摄食是驯养成功的关键因素之一，活沙蚕是好的开口饵料。营造好的驯养环境和及时药物处理能缩短驯养时间和提高成活率。驯养雌、雄性比以1：3～4为宜。借助生殖调控措施，春、夏季获取的野生鱼秋季就可产卵，好卵占23．4％。     

Soil Properties Required by Some Southern Africa Fruit Trees as Assessed by Discriminant Analysis

Some indigenous fruit trees, in the drylands of southern Africa are worthy of interest because of their adaptation to environmental conditions prohibitive for traditional crops. Their fruits or their derivatives are traditionally used as an additional income by rural population, but little information is available about the properties of the soils that support their growth, although this information is necessary if the trees are subjected to sustainable domestication. Several soil properties are, however, to be considered as a whole and discriminant analysis provides a helpful tool to individuate the best conditions for the tree growth. Thirty-five soil samples were taken in areas where the trees naturally grow and produce, and the analytical data of the surface layer were used to relate soil properties to tree species. Four groups of trees were well separated using two discriminant functions that takes into account both the fertility characteristics (pH, organic C, N, texture, and properties of the exchange complex) and the Fe contents and distribution among the oxide forms. The discriminant functions allow a very acceptable reclassification of the data (more than 80% of cases correctly reclassified) and the classification coefficients were used to build an empirical equation that may help to identify the most suitable tree to be introduced at a new site.     

Genetic structure of highland papayas (<Emphasis Type="Italic">Vasconcellea pubescens</Emphasis> (Lenné et C. Koch) Badillo) cultivated along a geographic gradient in Chile as revealed by Inter Simple Sequence Repeats (ISSR)

In Chile Vasconcellea pubescens is cropped to produce canned fruit, juice, jam and processed sweets. Additionally this species produces latex with a high level of papain, an important and valuable proteolytic enzyme with industrial applications. In this investigation seven ISSR primers were used to study the level and organization of genetic diversity in 333 samples of V. pubescens. Out of the 114 bands recorded, 63 proved to be polymorphic (P = 55.3%). At the species level, the genetic diversity was rather low (h = 0.01 ± 6,80188E-05, Shannon’s Index I = 0.16 ± 0,000148). The major portion of the genetic diversity was found within groups (65%). The genetic differentiation between the different groups was significant, as the AMOVA analysis suggested (Φ_pt = 0.35). When analysing the Northern area alone, the differentiation increased to Φ_pt = 0.40. When only the Southern area was analysed, Φ_pt decreased to 0.18, indicating greater genetic similarity among the samples. The results generated from Structure and Bayesian Analysis of Population Structure distinguished 8 genetically different groups, five of them located in the north and three in the south. The results are discussed in the light of the growers’ practices.     

食材还是玩物:古代鹌鹑驯养及利用考

鹌鹑作为著名的特种经济禽类,其驯化饲养已有几千年的历史。早在西周时期,鹌鹑就已经是祭祀献神的常用祭品,其后一直作为猎物与贡品被人们利用。唐代以后,鹌鹑逐渐成为皇室以及士人阶层的食材与玩物。至明清时期,"斗鹌鹑"在民间普遍盛行,鹌鹑的驯养技术得到了更广泛的实践。驯养鹌鹑和"斗鹌鹑"活动成为当时人们生活的重要内容,衍生出了具有中国传统特色的鹌鹑文化。