Breeding white clover for tolerance to low temperature and grazing stress

Summary Low temperature and grazing are the two major stresses limiting white clover yield in mixed swards grown in the marginal areas of the UK. White clover has traditionally been used to improve productivity in such areas but is increasingly being used to reduce input costs in more productive areas. Considerable genetic variation exists in characters associated with cold tolerance, low temperature growth and grazing tolerance. This paper describes recent progress in developing varieties tolerant to three major stresses and which give greater and more reliable production.     

Breeding tomato for pollen tolerance to low temperatures by gametophytic selection

Haploid selection for traits related to pollen cold tolerance in tomato was performed in segregating populations derived from a Lycopersicon esculentum × L. pennellii hybrid. BC₁ populations were obtained by combining normal and low temperature treatments on two stages of pollen development: pollen formation, and germination and pollen tube growth. F₁ hybrids were cultivated under low and normal temperatures and their pollen was used to pollinate L. esculentum plants at low and normal temperatures. The four BC₁ populations obtained were tested for the quality and quantity of pollen produced at low temperatures. The population obtained by cold treatment at both stages had a significantly improved pollen germination ability at low temperatures. The two other coldselected BC₁ populations showed no differences compared with the unselected BC population. A second cycle of pollen selection, corresponding to BC₂, was applied in order to test its persistence in the subsequent generations and the possibility to further improve the character. This second cycle showed no improvement although some plants retained the high pollen germination ability at low temperatures that was observed in the first cycle. Hence, gametophytic selection of some characters related with tomato pollen performance may be feasible, at least for the first cycle of selection.     

改进杂交法在紫甘薯资源创新利用及新品种选育上的应用

通过创新杂交方法,选育适合中国产业化发展的紫甘薯新品种。我们创新利用改进杂交法,并对其杂交后代进行改良或直接利用。结果表明：改进杂交法的单株平均结实率比人工定向授粉和辅助授粉分别提高20.8%~32.3%和14.6%~28.9%,后代紫心品系入选率分别提高7%~14.6%和30.4%~62.2%。利用该方法创新选育出优良亲本烟164、80、194。选育出优良新品系烟紫薯653、176、323、优良后备材料烟紫薯18、20,选育出优良新品种烟紫薯337。并初步探明：紫甘薯后代产量遗传主要受加性基因控制,后代紫心品系入选率的遗传部分受加性基因控制。     

Breeding for low nitrate content in radish (Raphanus sativus L.)

Summary To study prospects of reducing nitrate content of radish roots by breeding, plants with varying nitrate content were selected from four populations of the diploid cultivar Robijn (two populations with a low, one with an intermediate and one with a high nitrate content) and from two tetraploid cultivar, Boy and Oscar, with low nitrate contents.Correlation coefficients between nitrate contents of parent plants and their I₁'s were generally significant, but rather small (between 0.48 and 0.78), as were the parent-offspring regression coefficients (between 0.18 and 0.54). Significant differences in nitrate content occurred between I₁'s of each of the parent populations, I₁'s were also present with significantly higher or lower nitrate contents than the corresponding parent populations. Genetic variation for nitrate content was still present within I₁'s. I₂'s could be selected with a significantly lower or higher nitrate content than their I₁'s.It is possible to select radish cultivars with less than 2.0 mg nitrate per gram fresh weight of root under low light conditions in winter. As appeared from crosses with cytoplasmic-genetic male sterile plants, their was no relationship between cytoplasmic-genetic male sterility and nitrate content, indicating that hybrid cultivars with low nitrate contents can also be selected.     

Breeding for low input conditions and consequences for participatory plant breeding examples from tropical maize and wheat

Participatory plant breeding (PPB) has been suggested as an effective alternative to formal plant breeding (FPB) as a breeding strategy for achieving productivity gains under low input conditions. With genetic progress through PPB and FPB being determined by the same genetic variables, the likelihood of success of PPB approaches applied in low input target conditions was analyzed using two case studies from FPB that have resulted in significant productivity gains under low input conditions: (1) breeding tropical maize for low input conditions by CIMMYT, and (2) breeding of spring wheat for the highly variable low input rainfed farming systems in Australia. In both cases, genetic improvement was an outcome of long-term investment in a sustained research effort aimed at understanding the detail of the important environmental constraints to productivity and the plant requirements for improved adaptation to the identified constraints, followed up by the design and continued evaluation of efficient breeding strategies. The breeding strategies used differed between the two case studies but were consistent in their attention to the key determinants of response to selection: (1) ensuring adequate sources of genetic variation and high selection pressures for the important traits at all stages of the breeding program, (2) use of experimental procedures to achieve high levels of heritability in the breeding trials, and (3) testing strategies that achieved a high genetic correlation between performance of germplasm in the breeding trials and under on-farm conditions. The implications of the outcomes from these FPB case studies for realizing the positive motivations for adopting PPB strategies are discussed with particular reference for low input target environment conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Linkage relationships of genes for leaf morphology,flower color,and root nodulation in chickpea

Summary The allelic and linkage relationships among five chickpea (Cicer arietinum L.) morphological markers were investigated. When crossed with purple-flowered line ICC 640 and with each other, white flowered variety UC5 and mutant line PM974 were shown to carry non-allelic, single recessive genes for white flower color, provisionally designated w1 and w2, respectively. The single recessive gene conferring simple leaves in mutant PM299 was allelic to the previously described slv gene carried by variety Surutato 77, line ICC 10301, and other simple leaf chickpea mutants. In mutant 756M, a filiform leaf trait was controlled by a single recessive gene, fil, which was non-allelic to slv.The fil and w2 genes were linked, with recombination frequencies of 0.05 and 0.14 estimated from results of coupling and repulsion phase crosses, respectively. fil and w1 segregated independently. Root nodulation gene rn3 was closely linked to slv: recombination frequencies of 0.05 and 0.11 were estimated from results of coupling and repulsion phase crosses, respectively. A loose linkage detected between the w2-fil and the rn3-slv linkage groups will be the subject of further scrutiny.     

Breeding for low seed caffeine content of coffee (Coffea L.) by interspecific hybridization

Summary Seeds from open-pollinated flowers collected from hybrids of several Coffea species were analysed for caffeine content. The caffeine content was not always intermediary to that of the parents; higher and lower values were found. Diploid F₁ hybrids between accessions of C. eugenioides and C. salvatrix showed the lowest seed caffeine content. Seeds of the tetraploid hybrids C. arabica × C. salvatrix or C. arabica × C. eugenioides hybrids presented low caffeine content. The possibility of breeding coffee to reduce the caffeine content in the seeds by interspecific hybridization of C. arabica with other Coffea species is discussed.     

Genetic analysis in Chrysanthemum morifolium. I. Flowering time and flower number at low and optimum temperature

Summary The number of days to flowering and the number of flowers per plant were studied at 12, 13, 15 and 17 C night temperature in 79 F₁ populations from 15 parents. Only a few F₁ plants flowered earlier than their parents; the majority flowered at the same time, later or not at all. The number of flowers of the F₁ plants was higher than that of the parents.Genetic analyses showed a broad sense heritability of 70% for days to flowering and flower number and a highly significant GCA effect for days to flowering.The progenies and parents that flowered early at one temperature were generally early at all temperatures.     

Potato Breeding for Nitrogen-Use Efficiency: Constraints,Achievements, and Future Prospects

In this review, the genetic potential and efforts made on different aspects of potato breeding for nitrogen-use efficiency (NUE) and the possible physiological and genetic mechanisms determining NUE in potato in relation to other model crops are presented. Strategies to utilize the diverse gene pool of potato and improve the NUE in contrasting N environments are currently evaluated under field conditions using different selection approaches. So far, focused efforts have been made on the identification of potato genotypic differences which will allow for the analysis of specific components of nitrogen-use efficiency and the effect of nitrogen fertilizer on a range of physiological processes and morphological traits of potato. To my knowledge, despite the availability of genome sequence and QTLs identified for NUE and related agronomic and physiological traits in potato, and genomic information from other model crops, candidate genes on NUE have not yet been identified in potato. To maximize the success rate of potato breeding for NUE, basic knowledge how plants respond to different N regimes and other environmental conditions and use of DNA marker technology are vital.     

高大韧稻育种论

高大韧稻育种论是水稻育种上的一个新学说,也是今后的发展方向,主攻高产的目标.阐述了水稻由高秆到矮秆,现又由矮秆返高粗韧秆的有着本质不同的新飞跃.利用多年来实践获得的结果说明培育根发达、茎粗韧、秆适高、叶挺坚、穗长大、结实高、谷饱满是获得高产的关键,也是今后水稻育种的发展趋势.     

Breeding of Italian Ryegrass (Lolium multiflorum Lam.) for a low nitrate concentration by seedling test

In Japan, nitrate poisoning in ruminantscaused by the accumulation of nitrate inforage crops is a serious concern. In thisstudy, 3 cycles of phenotypic recurrentselection for nitrate concentration on adry matter basis were conducted for Italianryegrass (Lolium multiflorum Lam. cv.Nioudachi) to develop a breeding methodusing a seedling test. The seedling testinvolved the nitrate analysis of a shootfrom a plant grown for 6 or 8 weeks in thepresence of 50 mM KNO₃. The selectionintensity was approximately 0.07 for eachcycle. The realized heritability of thethird generation was calculated to be 0.21for seedlings and 0.57 for adult plants. Ina pot experiment, the nitrate concentrationof the adult plants of the third generationwas found to be 60% of the value for theoriginal population at an early headingstage. The reduction is related to theincrease in dry matter (DM) content as wellas the decrease in nitrate concentration ona fresh matter basis. The original andselected populations did not differ in theheading date. The concentrations of K, Nand P in the third generation decreasedwith the increase of DM content, whereas Caand Mg concentrations remained constant. Variation in the nitrate concentration wasfound among varieties on the market. Inconclusion, the ability to accumulatenitrate is a quantitative genetic trait ofItalian ryegrass and large-scale selectionfor the breeding of low nitrate populationsis possible using a seedling test.     

Breeding wheat and barley for winterhardiness

In 1951 the Foundation for Agricultural Plant Breeding, Wageningen, had a refrigerator and hardening equipment installed with the aim of providing private breeders with cold-resistant material and of testing their young lines for this character.This gave the author an opportunity of studying the problems of winterhardiness. The data gathered were treated in a thesis (2). This article gives a summary.     

辣椒新品种元辣红丰选育及配套栽培技术

对辣椒新品种元辣红丰选育过程、产量表现、品质鉴定及抗性检验,于2013年通过贵州省品种审定委员会审定,并总结出适宜于元辣红丰高产栽培技术.