Utilizing the frost resistance of diploid solanum species

Introductions of 13 frost-resistant diploid (2n=2x=24)Solanum species (2 non-tuberous) were inter-crossed to produce F₁ hybrids involving two frost resistance sources. Successful F₁ combinations were: (i) inter-crossed to produce hybrids involving 3 to 4 frost resistance sources, (F₁×F₁); and (ii) crossed with haploids (2n=24) of frost-susceptible tetraploid (2n=4x=48)S. tuberosum subsp.tuberosum, (F₁×tbr). Thirty-five of the 75 crosses between the 13 species produced viable seed. The F₁ and F₁×F₁ progenies segregated to yield plants more resistant to freezing temperatures than the parental species. All attempts to cross these hybrids with 24-chromosometbr were successful. Although tuber production improved following the first cross totbr, the frequency of resistant plants decreased approximately 50%. Thus far, all first back-cross attempts, (F₁×tbr)×tbr, have succeeded. Utilizing hybrids synthesized from several sources of frost resistance as the donor parents, and clonal selections of 24-chromosometbr as the recurring parents, may provide a high order of resistance throughout the backcrossing program and implement selection of frost-resistant, long-day tuberizing parental stocks acceptable to the potato breeder.     

Resistance in tuber-bearing solanum species to root knot nematode,Meloidogyne incognita

Forty-one clones of 34 accessions belonging to 25 tuber-bearingSolanum species were tested for their reaction to root knot nematode,Meloidogyne incognita. A high degree of resistance was found inS. bulbocastanum, S. gandarillasii, S. lignicaule, S. ajanhuiri andS. tuberosum groupandigena. S. vernei andS. spegazzinii were the most resistant species.     

Alaska Frostless,an inherently frost resistant potato variety

A potato clone with frost resistant foliage designated Alaska Frostless has been selected from the progeny of crosses involvingSolanum acaule and commercial varieties. Its chromosome number is (2N=5X=60). Nearly mature vines have withstood field frosting at?3 C for 2 hours and have recovered from several frosts of?2 C. Yields in cwt per acre of tubers 2–3.5 inch in diameter have equaled those of Alaska's standard varieties. Dry matter of 21.7% is equivalent to that of the Green Mountain variety. Tubers are flattened, round, smooth and white with a nonuniform faintly purple blush after exposure to light. Culinary quality, flavor, and texture are very good.     

Frost resistant potato hybrids viaSolanum acaule,Bitt. Diploid-Tetraploid crosses

Solanum juzepczukii Buk. andSolanum curtilobum Juz. et Buk. are two important primitive cultivated species of potato which are planted in the highlands of Peru and Bolivia. Little natural variation exists within these species. Crosses were made to artificially recreate these species using tetraploid cultivated potatoes as female parents and triploids derived from acaule-diploid crosses as males. The new hybrids were tetraploid (2n = 48) with a high degree of heterosis and variability, and several potential cultivated clones possessing valuable characters such as yield, earliness, frost tolerance and good tuber type were selected.     

蓖麻杂交组合收获指数评价

为了提高蓖麻杂交育种效率,研究杂交组合收获指数与性状之间的关系,观察和测量了133个蓖麻杂交组合的13个农艺性状,即收获指数、单株产量、生物量、百粒重、有效穗数、一级分枝数、株高、茎粗、主茎节数、主穗长、主穗位高、叶绿素含量、净光合速率。采用相关分析和回归分析研究133个杂交组合的农艺性状间的关系。结果表明,不同蓖麻杂交组合的收获指数差异较大,变幅为0.126~0.644,平均值为0.398;133个杂交组合中收获指数在0.5以上的组合仅占16.54%。相关关系结果表明,收获指数与单株产量呈极显著正相关,与主穗长呈极显著负相关。回归分析表明,单株产量、株高、主穗长、有效穗数4个性状对收获指数的影响较大。因此在育种过程中,选择主穗花序较长、植株相对较高、一级分枝数较多的个体,可提高育成材料的单株产量。     

Production of somatic hybrids between frost tolerantSolanum commersonii andS. Tuberosum: Protoplast fusion,regeneration and isozyme analysis

Mesophyll protoplasts ofSolanum commersonii, a frost tolerant wild species not crossable with the cultivated potato, were fused with either dihaploid or tetraploid S.tuberosum. Protoplasts were aggregated by means of alternating current (AC) or polyethylene glycol (PEG), and electrofused with three direct current (DC) pulses. The treatments with PEG/DC generally resulted in very low heterofusion frequency and protoplast viabiity. On the other hand, AC/DC fusion conditions were optimized by increasing the fusion density of protoplasts and adding CaCl₂ to fusion medium. When a density of 4.8 × 10⁵ protoplasts ml^?1 was used in the fusion medium containing 0.2 mM Ca⁺⁺, AC/DC treated protoplasts showed heterofusion frequencies and plating efficiencies of about 10 and 3%, respectively. Fast growing calli from AC/DC fusion experiments were further cultured for regeneration. Fifty-seven plants were regenerated and clonedin vitro as shoot cultures. Compared to parents they showed heterotic vigor and could be identified as hybrids, based on isozyme analysis.     

Identification of potato interspecific hybrids resistant toVerticillium wilt and determination of criteria for resistance assessment

Summary Verticillium dahliae causes potato (Solanum tuberosum) early dying disease. Interspecific hybrids containingS. tuberosum, S. berthaultii, S. bukasovii, S. chacoense, S. gourlayi, S. sparsipilum andS. tarijense were identified with resistance toV. dahliae. Clones were grown in replicated trials for three years in a plot containing approximately 50 colony forming units (cfu)V. dahliae per g soil. Clones were evaluated for vine maturity, early dying symptoms and stem colonization. Five resistant 2x clones were identified with early maturity and low levels of stem colonization. A single maturity score and one disease score, each obtained in mid-August, were sufficient to distinguish among clones. An effective threshold level for considering a stem to be infected was determined to be 25 cfu/100 μl sap. Early dying symptoms did not correlate strongly with stem colonization. Numerous stems must be sampled when making resistance assessments. The average cfu/100 μl sap correlated strongly with the number of infected stems.     

Evaluation of phenolics and antioxidant activity of black sorghum hybrids

Black sorghums possess very high levels of the rare 3-deoxyanthocyanidins which can be used as natural food colorants with health benefits. However, these sorghum genotypes have undesirable agronomic properties (i.e. high height, low yield, increased weathering). Black sorghum hybrids with improved agronomic properties were developed and their phenolic profiles and antioxidant activity were compared with black sorghum lines. Black sorghum hybrids were significantly lighter in colour than the lines (P < 0.001). All hybrids had a pigmented testa which was indicated by the presence of condensed tannins, which significantly increased total phenol levels and antioxidant activity. The 3-deoxyanthocyanidin, flavan-4-ol, and flavone levels were significantly lower in the hybrids (P < 0.001) and were strongly correlated to pericarp colour (P < 0.001). Flavanone levels were not significantly different among the lines and hybrids (P > 0.05) and pericarp colour did not affect their levels (P > 0.05). Even though the 3-deoxyanthocyanidin levels were lower in black sorghum hybrids than in the lines, the presence of condensed tannins in the hybrids significantly increased their antioxidant activity. Since 3-deoxyanthocanidin levels were dependent on pericarp colour, hybrids with increased blackness intensity should be developed to increase the stable 3-deoxyanthocyanidins.     

大豆抗锈种质的评价

对14个国内外大豆抗锈种质在福建地区的抗锈性及农艺性状进行了评价。结果表明:抗锈基因Rpp1、 Rpp2、Rpp3和Rpp4 (屏南豆)的抗性已被克服,抗锈种质樟子乌、九月黄和日向可能含有新的抗锈基因。来自国外 的抗锈种质在福建地区未能表现出对锈病的抗性,农艺性状较差,不适宜直接利用。     

Breeding behavior of resistance to green peach aphid in tuber-bearing Solanum germplasm

Fifty-seven tuber-bearingSolanum progenies including species and interspecific hybrid derivatives were evaluated for resistance to green peach aphid (GPA),Myzus persicae (Sulzer), using an excised leaflet test. The progenies segregated for resistance and most contained some highly resistant clones. Resistance appeared to be partially dominant and genotype-environment interaction was low. Heritability estimates of 50–60 percent were obtained from both diploid and tetraploid populations.     

Longevity of true seed from tuber-bearing and closely related non-tuber-bearingSolanum species

Information on the longevity of true seed from the tuber-bearing and closely related non-tuber-bearing Solanums was compiled from data obtained by the U.S. Inter-Regional Potato Introduction Project (IR-1), Sturgeon Bay, Wisconsin. Seed was stored at 1–3°C after drying to about5% moisture content. Several species exhibited high percentages of germination after 20 to 28 years of storage. Many other species also demonstrated no major decrease in germination during storage periods of 8 to 20 years. For some species germination data were erratic and no conclusions could be made as to the length of time their seeds could be stored and still remain viable     

Evaluation of a dry corn fractionation process for ethanol production with different hybrids

The effect of a specific dry fractionation process (FWS fractionation process) was evaluated on final ethanol and glucose concentration of 11 yellow dent corn hybrids in this dry grind corn process. In dry fractionation a dry de-germ de-bran process (similar to conventional corn dry milling) is used to separate germ and pericarp (bran) fiber prior to fermentation of the endosperm (grit) fraction. Fermentation results of grits produced from the FWS process were similar to whole corn samples and better than previously reported results on fermentation of grits from other dry fractionation processes. Further investigation showed that the amount of fat in FWS fractionated grits were 2–5 times more than grit samples from a commercial corn dry milling plant; suggesting reduced germ separation with more than 50% of germ not recovered and lost with the grits fraction. Final ethanol concentration for different corn hybrids varied from 12.7 to 13.8% (v/v) for whole corn and 13.4 to 14.7% (v/v) for grits samples. Dry fractionation (removal germ and bran) prior to dry grind processing, significantly affects the fermentation characteristics of corn hybrids. Corn dry fractionation can increase final ethanol concentration and recover germ and fiber as valuable coproducts.     

Disomic inheritance of anthocyanins and flavonol glycosides in the Tetraploid tuber-bearing speciesSolanum stoloniferum

Ten clones ofSolanum stoloniferum Schlechted (2n — 4x — 48) were selected from seedling populations that were produced by self-pollinating five introductions from the Commonwealth Potato Collection. These clones were used to produce S₁, F₁, F₂, and testcross populations. Clones and their progeny were scored for anthocyanins and flavonol glycosides in their corollas, stems, and leaves. Thin-layer chromatography (TLC) was used to separate and identify polyphenol compounds. No segregation for eight traits was observed within S₁ and F₁ families. Segregation was observed in F₂ and testcross populations for anthocyanins (derivatives of delphinidin and cyanidin, inhibited when the geneF is homozygous recessive); and flavonol glycosides (Q4 = quercetin 3-glucosyl-rhamnosylglucoside, controlled by the geneG1; and L1 = luteolin 7-glucoside, controlled by the geneL1) extracted from corollas. Observed ratios fitted ratios expected for disomic inheritance, differed from expected tetrasomic ratios, and provided additional evidence that the parental clones are homozygous. GenesF, G1, andL1 were genetically independent in dihybrid and trihybrid F₂ crosses.     

Yield and agronomic performance of maize hybrids resistant to the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

This study evaluated improved maize hybrids (Zea mays L.) with varying level of resistance to the maize weevil, Sitophilus zeamais Motschulsky, for yield and agronomic traits for two seasons. A total of 22 improved maize hybrids and three commercial standards were tested. Out of the 22 tested, two hybrids CKPH08035 (7.4–9.9 t ha⁻¹) and CKPH08039 (7.3–9.8 t ha⁻¹) significantly out yielded the commercial standards WH505 (8.8 t ha⁻¹) and BH140 (5.5 t ha⁻¹). In addition to yield, the improved hybrids also possess desirable traits including good plant height, good plant and ear aspects and good husk cover. The hybrid CKPH08004 had the lowest Dobie index of susceptibility and was regarded as resistant to S. zeamais. Weevils fed with the resistant hybrids produced low numbers of F₁ generation weevils, had a high median developmental time and a low percentage of grain damage and grain weight loss. An increasing number of F₁ generation resulted in an increasing grain damage and grain weight loss. We found an inverse relationship between the susceptibility index and percent mortality. However, the numbers of F₁ generation, percent grain damage and grain weight loss were positively correlated with the susceptibility index. The use of resistant maize hybrids should be promoted in managing S. zeamais in stored maize under subsistence farming conditions in Africa.     

Crossability of some green-peach-aphid-resistant tuber-bearing solanums,potential bridging species,andSolanum tuberosum ssptuberosum

Blue light fluorescence microscopy was found to be a quick and easy procedure for assessing pollen tube development in interspecific pollinations ofSolanum. Based on penetration of pollen tubes to the base of the style, several combinations of green-peach-aphid-resistant species and potential bridging species to S.tuberosum ssp.tuberosum should be considered for embryo culture. Sterile or highly infertile hybrids were obtained between green-peach-aphid-resistantS. tuquerrense andS. tuberosum ssp.tuberosum and are described. Slightly fertile hybrids were obtained betweenS. tuquerrense andS. polytrichon, a species compatible withS. tuberosum ssp.tuberosum.