Breaking the crossability barriers between disomic tetraploid Solanum acaule and tetrasomic tetraploid S. tuberosum

Summary A combination of compatible second pollinations and embryo rescue was applied for systematic production of true tetraploid hybrids from crosses between disomic tetraploid Solanum acaule and tetrasomic tetraploid potato, S. tuberosum. Several genotypes of tetraploid potatoes were pollinated with S. acaule, and the compatible second pollinations were made on the following day, with a genotype of S. phureja, IvP 35 to promote fruit development. Embryo rescue was carried out in 21 families, 14 to 27 days after the first pollination. A total of eight plants were obtained from the embryo rescue and their chromosome numbers were counted in the root tips. Three of the eight plants were identified as tetraploid, and five others as diploid. Morphology, isozyme banding patterns, and pollen stainability, as well as potato spindle tuber viroid (PSTVd) resistance, indicated the hybrid nature of the three plants. This is the first report of successful tetraploid hybrid production between disomic tetraploid S. acaule (4x) and tetrasomic tetraploid potatoes. Seed set from the crosses between one of hybrids and diploid potatoes indicated workable levels of both male and female fertility for introgression of valuable genes from S. acaule into the cultivated potato gene pool. The methodology used may be applied to other disomic tetraploid tuber-bearing Solanum species and with some modifications also to distantly related solanaceous species and genera.     

Selection of vigorous and fertile S-homo- and heterozygous tester clones from self-incompatible diploid potato, Solanum tuberosum L.

For the selection of diploid (2n = 2x = 24) potato (Solanum tuberosum) genotypes that are useful for the molecular and genetic analysis of the phenomenon of gametophytic self-incompatibility, three different types of basic populations were investigated. These populations were derived from three primary dihaploid clones, G609, G254 and B16, which possessed the S-allele combinations S1S2, S1S3 and S3S4 respectively. In order to select highly vigorous, profusely flowering, fertile and tuberising progenies, three types of populations, derived from the above mentioned diploid genotypes, were screened for performance and classified for the expression of self-incompatibility. Although the selection for well defined S-genotypes was sometimes complicated due to the occurrence of pseudo-compatibility and of a self-compatibilising factor, the use of a combination of criteria, viz., Iso Electric Focusing (IEF), pollen tube growth in the styles and the extent of berry and seed set made the selection of sufficient representatives of all six types of S-heterozygotes (S1S2, S1S3, S1S4, S2S3, S2S4 and S3S4) possible. After evaluating the strength of the self-incompatibility reaction in these heterozygotes, those with high expression were selfed, and intercrossed within their S-allele incompatibility group through the method of counterfeit pollination. In these progenies, well-performing S-homozygotes (S1S1; S2S2; S3S3; S4S4) for all four S-alleles with high expression of self-incompatibility were selected. As a result, all possible S-homo- and heterozygous genotypes with a predictable type of self-incompatibility are available and maintained both vegetatively and as botanical seed. The development of this material has paved the way for more critical analysis of molecular factors involved in self-incompatibility in diploid potato. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of an augmented nitrification assay to elucidate the effects of a spring barley crop and manures on temporal variations in rates

The effects of crop plants and farmyard or poultry manure applications on temporal variations in nitrification rates were measured in a field experiment. In order to elucidate factors which may have been governing such rates, an augmented nitrification assay was applied. The basis of the assay was to measure nitrification rates under circumstances where substrate, i.e. ammonium-ion, and water and spatial constraints had been removed. Nitrification rates showed marked temporal variation, of over one order of magnitude, throughout the growing season. Nitrification rates were also similarly increased when substrate and spatial constraints were removed, but distinct temporal variations still persisted. The pattern of such variations varied according to assay conditions in the augmented nitrification assay. Barley plants had a statistically significant effect on nitrification rates, positive early in the growing season and negative at the end. Manures stimulated nitrification, with poultry manure having a greater effect than farmyard manure, and there was evidence for a relationship between heterotrophic and autotrophic activity. Factors other than ammonium-ion concentration and water or spatial restrictions must also regulate nitrification rates in mineral soils; these could include population size or interactions. Received: 7 January 1996     

K型小麦雄性不育系诱导单倍体胚的胚胎学观察

从胚胎学方面研究了粘果山羊草细胞质的小麦雄性不育系K83(21)35A与保持系83(21)35B杂交的双受精过程,胚和胚乳的发育特点,以及单倍体胚和孪生胚发生的规律。结果表明:双受精过程、胚和胚乳的发育与普通小麦自交相似。n型单倍体胚来自助细胞的孤雌生殖;n-n型双胚来自助细胞和卵细胞的孤雌生殖;2n-n型双胚中的单倍体胚来自助细胞,二倍体胚来自受精卵。适当延迟授粉,能提高单倍体发生的频率。     

自然天敌控制小麦蚜虫的效果观察

田间试验表明：麦蚜天敌对小麦蚜虫的控制作用比较明显，其中七星瓢虫和草间小黑蛛为优势种，控制效果分别为28.5%和 23.2 %。采取充分发挥自然天敌的控制作用、高峰期辅以化学防治的综合治理策略，可有效地压低虫口基数，把蚜虫控制在穗前，以减轻蚜虫对小麦的为害。     

中国樱桃授粉结实和果实发育的研究

中国樱桃短柄和尖嘴品种在日平均气温4～5℃花芽开始萌动,12℃左右开花,14℃左右盛开。在10～25℃范围内花粉发芽率随气温上升而增高。在15℃条件下花粉经过4～8h开始发芽。短柄樱桃花粉发芽适应的气温范围广,低温下发芽率高于尖嘴樱桃。雌蕊授粉结实能力一般持续4～5 d,阴雨潮湿天气相应延长。以开花后1 d授粉的座果率为最高,第6 d明显下降。开花后4 d内平均气温和座果率呈直线回归,达到显著水平。以自然传粉的授粉方式,座果率为最高,同品种不同单株授粉座果率低,但高于自花授粉。樱桃有3次落果高峰,采前落果严重。果实生长期从盛花至果熟约47～55d.果实鲜重增长最快时间在采前10～15d.果肉干重在采前15d达到高峰。果实纵横径增长均表现为迅速生长。     

湖南地方梨资源研究Ⅲ.保靖阳冬梨若干特性研究

对保靖阳冬梨的植物学性状和生物学特性进行了观察，经人工授粉试验和人工杂交试验结果表明：保靖阳冬梨晚熟、味甜、耐藏、抗病，可溶性固形物达15．5％；它的自花结实率低，异花授粉结实率高，但胚囊育性强，可作为杂交母本；它与所试验的杂交母本杂交，都可得到杂交种子，说明花粉育性好，也可作为杂交父本。与黄花梨相比，保靖阳冬梨花粉粒大小均匀，形状规则，表面穿孔稀。     

"性别控制液"在奶牛繁殖上的应用

利用性别控制液对奶牛进行性别控制,试验组产母犊率56.25％,对照组48.15％,χ~2检验差异不显著(p>0.05),说明此性别控制液时提高奶牛后代母犊率没有显著影响。     

蜂蜜花粉悬浊液对苹果梨的喷雾授粉效果

本文对苹果梨盛花期喷蜂蜜花粉悬浊液对花序座果率及果实品质的影响进行了研究，发现蜂蜜花粉悬浊液比常用的蔗糖花粉悬浊液座果率提高１１～１５．３％，差异显著。但与传统的生产上广泛应用的人工鸡毛授粉相比二个供试果园结果不一致，这尚待进一步探讨。所用蜂蜜浓度不宜低于０．５％，花粉浓度不宜低于０．０５％，盛花期喷雾二次为宜。此外，蜂蜜花粉悬浊液喷雾授粉具有座果均匀、疏果量小、花粉用量少等优点。     

土地退化经济学分析与防治对策

中国土地退化普遍存在,全国退化土壤总面积为4.65亿hm2,占国土面积的48.44%,局部地区退化严重,中度以上(含中度)退化土壤面积1.58亿hm2,占34%。笔者从经济学的角度剖析土地退化的深层原因。发现私人利益、集团利益与国家利益不一致时,受集团势力的影响,政策难以发挥作用,导致土地过度使用;外部不经济性难以实现内部化,导致土地破坏严重;地权“四权”分离导致土地护理不力、滥占严重。针对土地退化的原因,提出行政干预、完善法律、经济手段以及工程技术等防治措施,共同防治土地退化,可较好达到防治的预期目的。