Tuber yields of families from open pollinated and hybrid true potato seed

This work was undertaken to compare the tuber yields, vegetative vigor and uniformity of seedling transplants obtained from different breeding methods. Twenty hybrid families from different groups of crosses involving 4x clones and 2x Phureja-haploid Tuberosum hybrids; 4x × 4x, 4x × 2x (FDR), 4x × (4x × 2x), and (4x × 2x) × (4x × 2x) and eleven open pollinated families from 4x clones, and 4x hybrids from 4x × 2x crosses were compared in a replicated yield trial. Families from 4x × 2x (FDR) crosses were the highest yielding among the hybrid groups having approximately twice the yield of the open pollinated 4x clones. They also were the best group in relation to plant vigor and uniformity. Based on these results, it appears that a good breeding scheme for high-yielding and uniform progeny from true potato seeds is the 4x × 2x hybridization method where the male parent is capable of producing 2n pollen via a first division restitution mechanism.     

Performance of haploid x wild species, 2x hybrids (involving five newly evaluated species) in 4x × 2x families

The 4x × 2x breeding scheme in potato allows introgression of germ-plasm from the 2x wild species into the cultivated tetraploid. Eighteen 4x × 2x, forty-five 4x × 4x, seven 4x-selfs, and five open pollinated (OP) families were transplanted in a randomized complete block design with two replications and 18 plants per family per replication. The 2x parents of the 4x × 2x families were seven haploid x wild species hybrids. These hybrids involve five 2x, wild species,Solanum bukasovii, S. gourlayi, S. muhidissectum, S. vermi, andS. verrucosum, which had not previously been evaluated in the 4x × 2x breeding scheme. Data were recorded for family yield, maturity, tuber uniformity, tuber number, and general tuber appearance. The 4x × 2x families as a group performed as well as or better than the 4x × 4x, 4x-self, and 4x-OP groups for all traits except maturity. Within family maturity distributions for 4x × 2x families indicate the possibility to select early maturing clones from high yielding families. Eleven of the fifteen families in the top 25% of the 4x × 2x and 4x × 4x families for yield were 4x × 2x families. Three of the four 2x parents evaluated for parental performance gave highly significant responses for increased yield. 4x × 2x families with Chiquita as a parent were the poorest yielding while several of the 4x x 4x families of which it was a parent were among the highest yielding: This indicates that the benefits of maximum heterozygosity may be overridden if the percentage of unadapted germplasm is too high.     

Aneuploid hybrids from 5x − 4x crosses in potato: Chromosome number, fertility, morphology and yield

The objective of this study was to characterize sixS. commersonii - S. tuberosum progenies deriving from 5x ? 4x crosses to provide evidence that they can be used in potato breeding. Hybrids analyzed (coded PTH) had a chromosome number between the 4x and the 5x level. In particular, progeny means for chromosome number ranged from 50±0.5 to 54±0.7, with most (70%) genotypes exhibiting a low aneuploid level of 48 to 53 chromosomes. Despite being aneuploid, the hybrids did not generally show phenotypic aberrations or vigor reduction common to aneuploids of other species. Most genotypes resembledS. tuberosum in growth habit, whereas corolla type, eye depth, and stolon length varied between and within progenies. Aneuploid hybrids produced tubers under long-day conditions. However, tuber yields were not as high as expected, probably due to lack of adaptation of theS. commersonii genome to long-day conditions. Although aneuploidy has often been associated with reduced male and female fertility, many 5x ? 4x hybrids were fertile in crosses withS. tuberosum. The average berry set and number of seeds/berry were 33% and 34.7, respectively, following PTH ×S. tuberosum crosses, and 40% and 51.7, respectively, forS. tuberosum × PTH crosses. The useful variation for fertility and tuber traits found in this material is being used for further breeding efforts.     

Male fertility and 2n pollen production in haploid-wild species hybrids

Hybrids (2n = 2x = 24) from crosses between Group Tuberosum haploids (2n = 2x = 24) and 24-chromosome, wild species must be fertile and produce 2n gametes if they are to be used in breeding schemes involving sexual polyploidization. Male fertility of the 2x hybrids depends primarily on the species parent. Hybrids involvingS. berthaultii, S. chacoense, S. kurtzianum, S. spegazzinii, andS. tarijense as parents are male fertile. The haploid parents are male sterile, so the species not only contribute genetic diversity and desirable traits, but also genes necessary for male fertility.S. infundibuliforme, S. raphanifolium, andS. sanctae-rosae parents produced male sterile hybrid progeny, while use ofS. boliviense, S. bukasovii, S. canasense, S. microdontum, andS. sparsipilum results in families containing both fertile and sterile plants. Sterility may be due to interactions between Tuberosum cytoplasm and dominant nuclear genes from the species. Genetic male sterility and environmental conditions may also be responsible for low pollen stainability in some hybrids. Many fertile, 2x hybrids produce 2n pollen. Selection for 2n pollen in the species is fast and efficient, but meiotic analysis is required in male sterile haploids. Fortunately, selection in the species parent alone results in a large number of 2n pollen-producing hybrids. These 2x hybrids have been used to generate tetraploids via 4x × 2x crosses.     

Performance of true potato seed families. 1. Effect of level of inbreeding

Summary Successive generations of open pollinated (OP) true potato seed (TPS) families represent a low-cost planting material. This study was conducted to determine whether inbreeding occurred during two successive OP generations and, if so, whether it adversely affected the performance of transplant families from true seed. Potato seedling transplants from 4x×2x hybrid, OP₁, OP₂, S₁ and S₂ families were compared for plant vigour, flowering, pollen stainability, OP fruit set, tuber yield and specific gravity. Hybrids were consistently superior, while S₂ families were inferior. The performance of OP₁, OP₂ and S₁ families did not differ significantly for most traits. The accumulation of inbreeding in successive OP generations was limited by reduced OP seed production on selfed plants; thus, a synthetic TPS variety propagated by open pollination may be feasible. Paper no. 3162 from the Department of Genetics, University of Madison.     

Breeding for 2n egg production in haploid × species 2x potato hybrids

The identification of diploid(2x), Tuberosum haploid × wild species hybrids (HS) which produce high frequencies of 2n eggs and have good tuber appearance is important for obtaining 4x progeny from 2x × 2x crosses in potato. More than 1700 HS clones were screened for the occurrence and frequency of 2n eggs through 2x × 4x crosses during two pollination periods. The resulting seed/fruit provides an estimate of 2n egg frequency. About 650 HS clones produced 2n eggs; 63 had 10–114 seeds/fruit; and 27 were selected for good tuber type. There was a large variation in seed set after 2x × 4x crosses, both within and between clones. Comparison of fruit and seed set between the two pollination periods using the same 595 clones indicated that environmental factor significandy affected 2n egg frequency. The mode of 2n egg formation was mainly due to omission of the second meiotic division controlled by a recessive gene (os). The gene frequency foros varied from 0.28 to 0.76 among six, 2x taxa. Both additive and dominance variance were significant for seed set after 2x × 4x crosses. Narrow sense heritability was estimated as 0.24. The average degree of dominance was equal to 1.66 which could indicate overdominance. Alternatively, this could be due to linkage disequilibrium,i.e. pseudooverdominance. However, dominance variance was greater than the additive variance indicating recurrent selection can be useful for improving the frequency of 2n egg production in the 2x population. The selected individuals, based on their phenotypic performance, should be progeny tested to identify the best parents for use in the next cycle of recombination.     

Yield and tuber characteristics of 4x progeny from 2x×2x crosses

Summary Unrelated, unselected 2x haploid-species hybrids that produce 2n eggs, by second division restitution and 2n pollen due to first division restitution were intercrossed to generate 4x progeny. The 19, 4x families were compared with seven cultivars for tuber yield, tuber appearance and tuber set. The mean yield of the 4x families was 30% higher than the mean yield of the cultivars. The best five 4x families outyielded the best five cultivars by 57% and 69% at two locations. Cultivars were superior for tuber appearance and tuber set. The high yields of the 4x families are due to genetic diversity of the 2x parents and their ability to transmit that diversity to the 4x progeny utilizing 2n gametes. The potential of the 2x×2x breeding method is dependent on developing 2x hybrid clones that form 2n eggs and possess desirable tuber types; clones producing 2n pollen and good tuber quality are available.     

马铃薯4x×2x杂种无性一代产量及产量性状的表现

产生２ｎ花粉的Ｎｅｏ－ｔｕｂｅｒｏｓｕｍ双单倍体×Ｓｏｌａｎｕｍｐｈｕｒｅｊａ的二倍体杂种以及其与Ｎｅｏ－ｔｕｂｅｒｏｓｕｍ双单倍体的回交后代与普通马铃薯（Ｓ．ｔｕｂｅｒｏｓｕｍｓｓｐ．ｔｕｂｅｒｏ ｓｕｍ品种东农３０３进行了杂交。４ｘ杂种在株高方面表现出了很强的杂种优势。商品薯产量与４ｘ亲本无显著差异，但两个杂种群体的最高值分别超４ｘ亲本的２６０ｇ／株和６０ｇ／株。总产量杂种优势明显，但杂种单株结薯数多，平均块茎重小，这些是限制４ｘ×２ｘ杂种利用的不利因素，需要进一步地改善。     

Resistance to soft rot (Erwinia carotovora subsp.atroseptica) in tetraploid potato families obtained from 4x-2x crosses

Diploid potato clones, interspecific hybrids ofSolanum species, having in their originS. tuberosum,S. chacoense, S. yungasense, S. phureja, S. gourlayi, andS. demissum, with resistance to soft rot, were crossed to tetraploid potato clones in 4x-2x crosses. The 24 tetraploid families obtained in a North Carolina II design were examined for tuber resistance to soft rot in a laboratory test and for basic agronomic traits in field trials conducted for two consecutive years. In addition, one family originating from a 4x-2x cross of two susceptible parents was tested. Statistical analysis of the data revealed significant general (GCA) and specific combining ability (SCA) effects, year, GCA (female) × year, GCA (male) × year, and SCA × year upon the inheritance of resistance to soft rot. About 35% of the progeny was selected as resistant to tuber soft rot, and of these 11% showed high resistance combined with good tuber yield, tuber weight, and tuber appearance. The relationships between resistance to soft rot and chosen agronomic traits were not noted or were weakly significant and sporadic. The resistance to tuber soft rot found in diploid potato hybrids can be transferred to the cultivated tetraploid pool through 4x-2x crosses, and a high frequency of offspring posses resistance.     

Male sterility and 2n pollen in 4x progenies derived from 4x×2x and 4x×4x crosses in potatoes

Summary The objectives of these experiments were to evaluate male sterility (MS) and 2n pollen frequency in 77 4x×2x families and 26 4x×4x families. The 2x parents were haploid-species hybrids and the 4x parents mainly clones withS. tuberosum ssp.tuberosum (tbr) andS. tuberosum ssp.andigena (adg) in their genetic background. The female parents had different cytoplasms: adg, tbr,S. demissum (dms), andS. stoloniferum (sto). Families from female parents with adg or dms cytoplasm did not have MS plants. However, families derived from crosses of many tbr females with 2x hybrids and a 4x adg clone had a high percentage of MS plants; all the progenies from cv. Serrana (sto cytoplasm) possessed tetrad sterility. These results can be explained as due to an interaction between a dominant male sterility (Ms) gene with tbr and sto cytoplasms. Some MS 4x hybrids (tbr×adg) used as females had the Ms gene, but male fertility was restored in some plants of their progenies when they were crossed with 4x tbr clones. This indicates that some tbr clones have a fertility restorer gene (Rt). The results from both 4x×2x and 4x×4x families fit the expected ratios assuming chromatid segregation for both the Ms and Rt loci. The gene frequency of parallel spindles was estimated in the 4x population as 0.74.     

Seed set in 4x x 2x crosses as related to 2n pollen frequency

Seeds per fruit following 4x × 2x crosses in potato are roughly related to the frequency of 2n pollen. Our goal was to examine precisely the relationship between frequency of stainable 2n pollen and seeds per fruit (s/f) in 4x × 2x crosses. A 4x cultivar with high female fertility and 21 2n pollen producing 2x hybrids were used as seed and pollen parents, respectively. 2n pollen frequencies varied from 1 to 99% in the 2x hybrids and seed set ranged from 0 to 305 s/f in 4x×2x crosses. Mean seeds per fruit increased in response to increases from 1 to 50% 2n pollen, but did not increase in response to using a pollen sample with a 2n pollen frequency over 60%. Seed set averaged 11 s/f corresponding to pollen samples with 1–5% 2n pollen, 50 s/f at 10–20%, 125 s/f at 20–30%, and over 170 s/f at 2n pollen frequencies over 60%. Seed set in 210 control 4x × 4x crosses indicated that equivalent seed set occurs in 4x × 2x crosses when 2n pollen frequencies are over 20–30%. The 2x hybrids differed in mean and variation of 2n pollen frequencies and seed set in 4x × 2x crosses. One 2x hybrid with a meiotic aberration (sy-3) resulting in all univalents at Metaphase I (ordinarily leading to male sterility) and parallel spindles (ps) at Anaphase II had close to 100% 2n pollen (of the stainable pollen) and gave equivalent s/f in 4x × 2x crosses to s/f in 4x × 4x crosses. It is apparent that ample seed set occurs for using the 4x × 2x breeding scheme with 2n pollen frequencies over 10% and that even very low 2n pollen frequencies (1–10%) provide seed for the 4x×2x breeding approach.     

属间杂交获得的甘蓝型油菜雄性不育材料的研究

采用蕾期剥蕾授粉的方法,成功获得了新疆野生油菜野油2000-1和甘蓝型油菜Parol属间杂种。杂种F1育性极低,自由授粉条件下获得少量F2种子。在F2群体中成功选择到一株雄性不育株,用Parol做轮回亲本与不育株回交,BC1、BC2和BC3群体中可育株与不育株均呈1﹕1分离。用波里马细胞质雄性不育的保持系和恢复系、681A的保持系和恢复系、隐性核不育86A的保持系及其它33个甘蓝型油菜品系与BC2群体中的不育株测交,测交后代可育株与不育株呈5﹕3分离的组合有20个,呈1﹕1分离的组合有14个,呈3﹕1分离的组合有3个,有一个组合的后代完全可育,表明该雄性不育材料可能为显性核不育。     

Erwinia resistance in backcross progenies ofSolanum tuberosum x S. tarijense andS. tuberosum (+) S. commersonii hybrids

Summary The resistance to tuber soft rot caused byErwinia carotovora ofSolanum tuberosum x S. tarijense andS. tuberosum (+) S. commersonii hybrids and their backcrosses is reported. A number of resistant diploid sexual hybrids and tetraploid/hexaploid somatic hybrids were selected. Backcross progenies were obtained through 2x×4x crosses involving a resistant diploid hybrid and tetraploidS. tuberosum, and through 4x×4x crosses between a resistant somatic hybrid andS. tuberosum. The hybrids showed high variability interms of resistance to tuber soft rot. The resistance of progeny from 2x×4x backcrosses was similar to that of the parental sexual hybrid. By contrast, the resistance of genotypes deriving from 4x×4x backcrosses was reduced compared with the resistant somatic hybrid. In general, tuber characteristics of the backcross hybrids improved considerably as compared with their parents, and tuber yield per plant was good.     

Performance of true potato seed families. 2. Comparison of transplants vs. seedling tubers

Summary A potato crop can be grown from true potato seed (TPS) either by transplanting seedlings to the field (seedling transplants) or by planting tubers derived from seedlings (seedling tubers). The effect of the planting method on performance of TPS families was evaluated for three types of families, 4x×2x hybrid, open pollinated, and self pollinated. Families from seedling transplants and seedling tubers and their 4x parental clones were compared for tuber yield and specific gravity. Families from tubers had substantially higher yields and significantly more uniform specific gravity than families from transplants. Hybrid seedling tuber families had a higher mean yield than the parental clones and did not differ from them in specific gravity. Selection in the seedling generation could further improve both OP and hybrid families from transplants and from seedling tubers. Paper no. 3163 from the Department of Genetics, University of Madison.     

A restorer gene for genetic-cytoplasmic male sterility in cultivated potatoes

Fifty-nine clones (cultivars and advanced selections) ofSolanum tuberosum Group Tuberosum were pollinated with two Group Phureja-haploid Tuberosum hybrids, which produce FDR 2n pollen (ps/ps) and are heterozygous for a dominant gene (Ms/ms) which interacts with Tuberosum cytoplasm to result in male sterility. Twenty-eight and thirty-four plants from each family were transplanted to the field in two different locations, respectively. Pollen samples were collected from each plant and stained with acetocarmine glycerol jelly. Plants with over 95% unstainable pollen were considered male sterile. The families could be put into distinct classes according to the ratio of male sterile to male fertile plants; 3 sterile: 1 fertile (23 clones), 2 sterile: 3 fertile (24 clones), 1 sterile: 5 fertile (3 clones), and 0 sterile: 1 fertile (3 clones). Four families deviated significantly from any expected ratio. The variation for male fertility among families resides in the tetraploid parent, since the male parents have the same genotype (Ms/ms) for theMs locus. The locus of this gene is very distal to the centromere such the 2n gametic output is 1 Ms/Ms : 2 Ms/ms : 1 ms/ms. The variation in male sterility is explained by the presence or absence of a dominant allele of a restorer gene (Rt) in tetraploid Tuberosum. This locus is also very distal to the centromere. The frequency of theRt gene was estimated to be 0.20 in Tuberosum. The finding ofRt gene explains some of the conflicting results in male fertility of haploid Tuberosum x 2x cultivated and wild species hybrids. It also provides an opportunity to partially circumvent this male sterility. Haploids (2n = 2x = 24) extracted from 4x clones withRt genes would have male fertile progeny in crosses with species carrying theMs gene.     

小麦光温敏核雄性不育系BS366和BS1086杂种一代结实率研究

为了解小麦光温敏核雄性不育系BS366和BS1086的育性恢复状况,评估恢复系人工定向改良对其恢复能力的效果,在不育生态区对以55份定向改良的恢复系和33份非改良恢复系(常规小麦)为父本配制的杂种一代的结实率进行了分析。结果表明,BS366和BS1086杂种一代结实率变化范围为15.42%～140.34%和20.28%～119.07%(国际法),平均结实率分别为73.02%和72.21%,二者差异不显著,说明2份母本的育性恢复能力差异不显著。BS366和BS1086杂种一代结实率主要分布于40%～110%和60%～100%间,BS1086杂种一代结实率分布更为集中。BS366和BS1086与改良父本的杂种一代平均结实率分别为84.45%和78.97%,与非改良父本的杂种一代平均结实率分别为53.97%和60.95%,改良父本的平均恢复力高于非改良父本,表明定向改良有利于提高恢复系的恢复力。BS366和BS1086与相同父本的杂种一代结实率差异在-41.66%～61.93%之间,表明相同父本对不同母本的育性恢复力存在差异。BS366和BS1086与相同改良父本的杂种一代中有61.82%的...     

Serogroups ofErwinia carotovora involved in systemic infection of potato plants and infestation of progeny tubers

Enrichment techniques and serological strain typing methods were used to determine the source of stem and progeny tuber populations ofErwinia carotovora (Ec) in 1980 and 1981. Plots were established in a field that had been planted with potatoes since 1972. Seed tubers of cultivars Russet Burbank and Norgold Russet were assayed forErwinia carotovora pv.carotovora (Ecc) andErwinia carotovora pv.atroseptica (Eca) by tuber peeling and direct plating and plating following enrichment in a pectate-based broth. Levels of seed tuber infestation ranged from undetectable to 2.4 × 10⁴ colony-forming units per g peel tissue. Prior to planting Ecc was detected in soil samples from field plots by enrichment in a pectate-based broth. Ec was isolated from symptomless plants with increasing frequencies from 8 weeks following planting regardless of the level of Ec populations in seed tubers. At harvest progeny tuber recontamination was low and not related to levels of seed tuber Ec populations. In 1980, serological typing of representative Ecc isolates indicated serogroups III, XXIX, and unknown strains isolated from the soil but not the seed tubers prior to planting were isolated from stems and progeny tubers. Serogroup XXIX was isolated from soil, seed, stems and progeny tubers in 1981. Throughout both years, Ecc was isolated more frequently than Eca from seed, soil, stems, and progeny tubers. These data emphasize the potential for reinfestation of seed stocks and infection of plants by populations of Ecc that overwinter in soil under Wisconsin conditions.     

2n pollen in eleven 2x, 2EBN wild species and their haploid x wild species hybrids

Summary Sixty-three plants producing 2n pollen were identified among 65 introductions of 11 2x, 2EBN wild species. They were found in 27 of the 65 introductions representing ten of 11 species. The gene frequencies for the allele controlling 2n pollen formation ranged from 0.19 to 0.65. Seventyeight haploid x wild species hybrid families were produced using the previously identified 2n pollen plants as male parents. One hundred and thirty-two plants that produced 2n pollen were identified among the haploid x wild species hybrids at one location and 44 at another. The high number of haploid x wild species hybrids that produced 2n pollen and the large number of hybrids with acceptable pollen stainability demonstrate the potential of the hybrids in 4x × 2x germplasm transfer. Potato breeders can unleash the genetic diversity present in the 2x, 2EBN wild species by screening them for 2n pollen and crossing the 2n pollen producing plants to haploids.     

Differences between hybrids ofSolanum tuberosum L. andSolanum circaeifolium Bitt. obtained from symmetric and asymmetric fusion experiments

Summary Potato plants obtained by symmetric and asymmetric protoplast fusion experiments withSolanum tuberosum andSolanum circaeifolium were compared and their potential use for plant breeding was investigated. For asymmetric hybridisation wild species tissue was irradiated with X-rays. Irradiation enhanced regeneration frequency. RFLP analysis showed that both techniques gave approx. 95% hybrids among the regenerates. Asymmetric protoplast fusion gave 22% regenerates with a ploidy level between 2x and 4x or 4x and 6x. None of the regenerates obtained from symmetric fusion had these ploidy levels. The tetraploid hybrids showed good male and female fertility. Male fertility was highest for the eutetraploid regenerates. With increasing asymmetry and with increasing ploidy level fertility decreased. Berry induction and seed production were observed for the eutetraploid and, to a lesser degree, for the hypotetraploid and hypohexaploid hybrids.     

Use of experimental tetraploids in potato breeding

High yielding experimental tetraploids from 4x × 2x crosses were found to be excellent parents, giving rise to many high yielding families and clones. Several of the progeny were found to yield over 900 cwt/acre at the Hancock Experimental Station. Both general and specific combining ability were significant for yield, while general combining ability was predominant for tuber appearance traits. Breeding methods to take both immediate advantage of the existing experimental tetraploids and to generate further experimental tetraploids that are of more desirable tuber appearance and possibly even higher yield are presented.