Glycoalkaloid accumulation during tuber development of early potato cultivars

Summary Plants of early potato cultivars were sampled at successive harvests during tuber development and individual tubers were analysed for α-solanine and α-chaconine using high-performance liquid chromatography. Mean tuber total glycoalkaloid concentration (α-solanine plus α-chaconine) per plant decreased with time and statistically significant differences between cultivars were observed in the patterns of decline during tuber growth. The mean tuber ratio of α-chaconine to α-solanine increased during tuber development and was also affected by genotype. Total glycoalkaloid concentration for individual tubers of marketable sizes (up to 50 g fresh weight) exceeded the safety limit of 20 mg per 100 g fresh weight for cultivars Home Guard and British Queen but not for Rocket. These differences were attributable to differences in both rates and patterns of glycoalkaloid accumulation during tuber development, although in all cultivars results were consistent with glycoalkaloid accumulation occurring in the expanding peripheral cell layers of tubers for a considerable period after tuber initiation.     

Amylolytic activity in stored potato tubers. 2. The effect of low-temperature storage on the activities of α-and β-amylase and α-glucosidase in potato tubers

Summary Tubers of the potato cultivars Record, Wilja, Pentland Dell and Brodick (formerly clone 137371) were sampled before and after storage at either 4°C or 10°C. Reducing sugar content stayed constant during storage at 10°C in all four cultivars but rose greatly during the first 6–12 weeks of storage at 4°C in Record, Wilja and Pentland Dell but not in Brodick. Amylolytic activity was determined after 5 weeks storage using blockedp-nitrophenyl maltoheptaoside as substrate for α-amylase,p-nitrophenyl maltopentaoside as substrate for β-amylase, andp-nitrophenylglucopyranoside as substrate for α-glucosidase. The values obtained from tubers stored at 4°C were higher than those from tubers stored at 10°C, the differences being much less in Brodick than in the other three cultivars.     

Einfluss von Lagerung und Sorte auf die Verteilung der Glykoalkaloide in der Kartoffelknolle

Zusammenfassung Fünf Speisekartoffelsorten wurden w?hrend einer sechsmonatigen Lagerung fünfmal auf α-Solanin und α-Chaconin untersucht. Es wurden vier Gewebebereiche der Knolle getrennt überprüft. Der Gesamtglykoalkaloidgehalt betrug im Augenbereich 164, in der restlichen Schale 101 und in der Gef?ssbündelzone mit ?usserem Speichergewebe 8mg/100g. Trockensubstanz. Im restlichen Innenk?rper waren nur noch Spuren (0.164mg/100g TS) nachzuweisen. Zwischen den Sorten und diesen Gewebepartien traten statistisch gesicherte Wechselwirkungen auf, die im wesentlichen von einer Sorte verursacht wurden. W?hrend der Lagerung sind die Alkaloidgehalte leicht, aber statistisch nicht gesichert gesunken. α-Solanin und α-Chaconin kamen generell im Verh?ltnis von etwa 1∶1.5vor; die Korrelation zwischen beiden Formen ist sehr eng (r=0.865). Bezogen auf die gesamte Knolle lagen die Gesamtglykoalkaloide je nach Sorte zwischen 2.4 und 8mg/100g Frischsubstanz und damit im gesundheitlich unbedenklichen Bereich.

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Summary Five table potato cultivars (Erna, Granola, Gusto, Ulse, Margit) from the same source were examined for their content of α-solanine and α-chaconine during a sixmonths storage period. For the testing and subsequent analysis the tubers were dissected into four kinds of tissues: eye-zone, peel, vascular bundle region, medulla. The total glycoalkaloid content (TGA) in the total tuber mass varied between 2.4 and 8mg per 100g fresh matter depending on cultivar (Fig. 1). Despite significant differences between cultivars (Table 1), all potato cultivars remained within the safe range during the entire storage period. Remarkable differences in TGA per 100g dry matter could be noted in the tuber parts. For the eye-zones a TGA of 164mg was found; the peel region showed 101mg and the vascular bundle zone 8mg. The medulla of the tubers contained only traces of TGA (0.164mg/100g dry matter, Fig. 2). The statistical analysis only revealed significant interactions between cultivars and tuber parts (Table 1), mainly caused by the cultivar Gusto which showed higher contents of α-solanine and α-chaconine in its vascular bundle regions (Figs 3–5). The ratio between amounts of α-solanine and α-chaconine was approximately 1∶1.5, and after eliminating effects of cultivar, storage and tuber parts, the correlation coefficient between amounts was 0.865. This close correlation can be used for breeding. The non-significant, slightly negative effect of the six-months storage period on alkaloid content was noteworthy. It is assumed that only after long storage periods or through inappropriate storage (sprouting of tubers) a significantly higher glycoalkaloid content may be expected.

     

Changes in the content of L-ascorbic acid,glucose, fructose,sucrose and total glycoalkaloids in potatoes (cv. Bintje) stored at 7, 16 and 28°C

Summary We investigated the changes in the content of L-ascorbic acid (L-AA), glucose, fructose, surose and total glycoalkaloids (TGA) during storage of potatoes, cv. Bintje, for 12 weeks at 7,16 and 28°C. The initial amount of L-AA was 8.2 mg/100g fresh weight; after 12 weeks' storage at 7°C it had decreased, while at 16 and 28°C it had increased. The sugar content went up most in potatoes stored at 28°C, but remained below the level at which potatoes taste sweet. The sugar content rose slightly at 16°C, while it decreased in tubers stored at 7°C. The initial TGA content, in equivalent amounts of α-solanine, was 3.6 mg/100 g fresh weight; after 12 weeks' storage it had decreased slightly at all three storage temperatures.     

Effects of early planting and cultivars on the yield and agronomic traits of soybeans grown in southwestern Japan

Early planting contributed to increased soybean yields in the U.S. Because a double-cropping system dominates in southwestern Japan, early planting is not performed; it is thus unclear how much the yield potential could be increased by early planting. To address this question, we planted seven U.S. and five Japanese cultivars on around 20 May (early planting), measured the agronomic traits, including yield, yield components, and oil and protein contents, and compared these traits with those of the same cultivars planted on around 20 July (normal planting). In the early planting, the yields of the U.S. cultivars were 322–453 g m^?2, whereas the highest yield among the Japanese cultivars was only 315 g m^?2, which is significantly lower than those of the top five U.S. cultivars, indicating the adaptability of U.S. cultivars to early planting. The increases in yield obtained with early planting were 99–199 g m^?2 and ?26–144 g m^?2 for the U.S. and Japanese cultivars, respectively. The yield obtained by early planting was positively correlated with the pods m^?2, seeds pod^?1, and oil contents, but negatively correlated with the sterile pod rate, 100 seed weight and protein content. In the early planting, the U.S. cultivars had greater pods m^?2, seeds pod^?1 and oil content and less sterile pod rate, 100-seed weight, and protein content than the Japanese cultivars. These results suggest that early planting can increase the yield in southwestern Japan, if cultivars with agronomic traits observed in the U.S. cultivars of this study are grown.     

An economically based evaluation index for perennial and short‐term ryegrasses in New Zealand dairy farm systems

Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs (Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha^?1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha^?1 to $863 ha^?1 year^?1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha^?1 year^?1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha^?1 year^?1 (depending on region) operating profit on dairy farms since the mid‐1960s.     

Biochemical Composition and Indigestible Oligosaccharides in Phaseolus vulgaris L. Seeds

Common beans have a high nutritional value, but contain galactooligosaccharides (GO), which cause flatulence and intestinal discomfort in humans. The biochemical composition of ten bean cultivars was determined to select those of high protein and low GO contents. The cultivars varied in carbohydrate (47.02–60.17%), GO (3.12 – 5.71%), protein (22.17–33.50%), lipid (1.13–1.81%), moisture (11.42–12.93%) and ash contents (4.08–5.61%). ‘Mexico 222’ presented the highest α-galactosidase activity. Protein and GO contents were positively correlated. ‘Perry Marrow’ combined high protein and low GO concentrations, indicating it can be used in improvement programs aiming at high-quality cultivars for human consumption.     

Preparative isolation ofSolanum tuberosum L. glycoalkaloids by MPLC

Summary A new, efficient and economic method employing Medium Pressure Liquid Chromatography (MPLC) for the isolation of the two majorSolanum tuberosum L. glycoalkaloids (α-solanine and α-chaconine) is described. Potato peelings are homogenised with 5% acetic acid, the glycoalkaloids purified by filtration through an XAD-2 column and then by precipitation from the aqueous solution. The resulting glycoalkaloid fraction was purified by MPLC using a Silica Gel column and a CHCl₃:MeOH:2% NH₄OH mixture (70∶30∶5) as mobile phase to yield pure α-chaconine and a-solanine. This methodology can be used to obtain glycoalkaloids for enthomology and toxicological research where large amounts of these compounds are required.     

Does the “high sugar” trait of perennial ryegrass cultivars express under temperate climate conditions?

The objective was to evaluate water‐soluble carbohydrate (WSC) and crude protein (CP) concentration of perennial ryegrass (PRG) cultivars with different genetic potential for producing WSC under two contrasting agronomic managements in temperate climate (southern Chile). A 4 × 2 factorial design was randomly allocated to 24 plots (31 m² each, three blocks): four PRG cultivars (diploid standard cultivar, “2nSt”; tetraploid standard cultivar, “4nSt”; diploid high sugar cultivar developed in New Zealand, “2nHSNZ”; and tetraploid high sugar cultivar developed in Europe, “4nHSEU”) and two agronomic managements (“favourable,” defoliations at three leaves per tiller and nitrogen (N) fertilization rate of 83.3 kg N ha^?1 year^?1; “unfavourable,” defoliations at two leaves per tiller and N fertilization rate of 250 kg N ha^?1 year^?1). Herbage samples were collected in early spring, spring, summer and autumn. Concentration of WSC did not differ among cultivars in spring and summer, averaging 194 and 251 g/kg DM, respectively. The cultivar 4nHSEU had the greatest WSC concentration in early spring and autumn (187 and 266 g/kg DM, respectively) and the greatest CP concentration across samplings (average 230 g/kg DM). Favourable management improved WSC concentrations in early spring and summer and decreased CP in spring, summer and autumn. Annual DM yield did not vary with cultivar or management, averaging 8.43 t/ha. Within a 12‐month study at one site in a temperate environment in southern Chile, PRG cultivars have not shown a consistent expression of the “high sugar” trait, where a genetic × environment interaction might be operating.     

A rapid method for the quantification of steroidal glycoalkaloids by reversed phase HPLC

Summary Methods were developed for clean-up of potato tuber extracts on solid phase extraction CN-cartridges and for analysis of steroidal glycoalkaloids by reversed phase HPLC. The alkaloids α-solanine, α-chaconine, α-solasonine and α-solamargine could be separated on C₈ or C₁₈ reversed phase columns using a mobile phase of acetonitrile/Tris-buffer (3∶2, v/v). The analysis time of tuber extracts containing these alkaloids was less then 4 min, if the pH of the mobile phase was adjusted to 7.4 and run at a flow rate of 0.5 ml/min.     

云南咖啡品种使用研究及创新应用

对云南咖啡种植规模、使用品种种类、育种背景及栽培特点进行了调研分析。证实了主栽品种卡蒂姆7963与P4是同一品种;对各品种的杯品质量进行了评价,多次杯品鉴定表明,生产上种植卡蒂姆类咖啡虽然内在品质赶不上波邦和铁比卡,但可通过加强水肥管理、遮荫栽培、高海拔种植和提高初加工水平等来提升咖啡杯品质量;对今后发展咖啡使用品种及应注意的问题提出了建议。     

Isolation of solanidine from haulm and tuber sprouts of potato (Solanum tuberosum L.)

Summary The kinetics of enzymatic transformation of total glycoalkaloids (TGA) in haulm and tuber sprouts of potato to solanidine and the kinetics of solanidine isolation from plant material were studied. The optimum reaction conditions for the enzymatic TGA transformation were found for haulm to be: plant material to liquid phase 1:4 w/v, temperature 35°C, pH 5.4; and for tuber sprouts: plant material to liquid phase 1:3 w/v, temperature 37°C, pH 5.4. The. maximum degree of enzymatic transformation of TGA in haulm and tuber sprouts of 65 and 75%, respectively, was achieved after 50h. Carbon tetrachloride was the best solvent for solanidine extraction from the plant materials. The optimum ratio of plant material to carbon tetrachloride for the isolation of solanidine was 1:8 w/v for both extraction cycles, ensuring a yield of solanidine of approximately 55 and 65% from haulm and tuber sprouts, respectively, after 30 min.     

Amylase activity in potato tubers

Summary Amylase activity in extracts of sprouted tubers was optimised at final concentrations of soluble starch in the incubation medium of 0.6–2.0 mg cm⁻³. Optimum pH was 6. The exclusion of calcium ions from extraction and incubation media did not result in reduced enzyme activity. This, together with a shift in the absorption maximum of the starch-iodine complex almost identical to that observed with pure β-amylase, indicates the predominance of β-amylase in the extracts. Over a 15-min incubation period the linearity of the response was dependent upon the volume of tuber extract included in the assay medium. Gel filtration of extracts did not influence this response.     

黑龙江省水稻新品系品质状况研究

选用16个目前黑龙江省较有希望推广的新品系,种植于省内4个积温带中的典型生态环境地点,初步分析了每个品系的品质表现。主要结果如下:供试材料品质性状除垩白大小外,国优一级达标率为25%以上,而国优二级达标率均在87.5%以上;比较而言,垩白度的降低应是重要育种目标之一;早晚熟品种在综合性状表现上各有优势,早熟品种的整精米率、垩白度、直链淀粉含量占优势;而晚熟品种在胶稠度、食味上占优势。     

A rapid quantitative determination of the individual glycoalkaloids in tubers and leaves ofSolanum tuberosum L.

Summary A rapid quantitative determination of the individual glycoalkaloids solanine and chaconine is described. The glycoalkaloids were extracted by blending with methanol and the dry residues obtained were worked up by extraction withn-butanol. After separation of them by thin layer chromatography, they were assayed by in situ fluorodensitometry of the chromatograms. The recoveries levels obtained by the newly developed extraction and work-up procedure were similar to those obtained by the method of Sachse and Bachmann. Potato tubers and leaves, and industrial potato protein were analysed with this method and its precision was equal or better than that of other methods. It can also be used as a semiquantitative thin layer chromatography assay of potato glycoalkaloids.

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Zusammenfassung Beschrieben wird eine schnelle und quantitative Bestimmung der Glykoalkaloide Solanin und Chaconin. Die Prim?r-Extraktion der Glykoalkaloide durch Eluieren mit Methanol wurde mit der nach der Methode von Sachse und Bachmann durchgeführten Extraktion unter Rückfluss verglichen. Nach dem Aufarbeiten der Extrakte durch Ausf?llung wurden die Glykoalkaloide dünnschichtchromatografisch (DC) getrennt und die Chromatograpmme durch in situ Fluorodensitometrie gemessen. Da sich keine signifikanten Unterschiede (α=0,05) zwischen den beiden Extraktionsmethoden ergaben (Tabelle 1) wurde die weniger arbeitsintensive Methode des Eluierens für die Extraktion der anderen Proben gew?hlt. Um die zeitaufwendige Methode des Ausf?llens zu umgehen, prüften wir für die Aufarbeitung zwei Modifikationen der von Crabbe & Fryer (1980) benutztenn-Butanol-Extraktion. Der trockene Rückstand der Prim?rextraktion wurde in einer Mischung gleicher Teile von Butanol, ges?ttigt mit einprozentigem Ammoniak und 1% Ammoniak ges?ttigt mitn-Butanol aufgenommen. Nach der Trennung der Schichten wurde die Butanolschicht für die quantitative DC verwendet. Bei der zweiten Modifikation wurde der trockene Rückstand in verdünnter Essigs?ure gel?st und zentrifugiert. Die klare saure L?sung wurde alkalisch gemacht und mitn-Butanol ausgechüttelt. Da in diesem Fall die Verwendung ges?ttigter L?sungsmittel nicht m?glich war, wurde ein Korrekturfaktor für die Volumenver?nderung dern-Butanol-Schicht bestimmt. Nach dem Schütteln blieben von den ursprünglich 10 mln-Butanol 9,5 ml übrig. Die Ergebnisse dieser beiden Aufarbeitungsmethoden wurden mit den durch Ausf?llung erhaltenen Ergebnissen verglichen (Tabelle 2). Bei der einfachenn-Butanol-Extraktion war die Trennung der Glykoalkaloide durch DC bei Proben mit einem geringen Glykoalkaloidgehalt insofern gest?rt als sich zu hohe Glykoalkaloidwerte ergaben. Die Extraktion mit Essigs?ure/n-Butanol ergab Werte, die gleich hoch oder geringfügig h?her waren, als nach der Ausf?llung. Die DC-Trennung der Glykoalkaloide wurde nicht durch andere fluoreszierende Substanzen gest?rt. Die Wiederfindungsrate der gesamten Methode: Eluieren und Essigs?ure/n-Butanol-Extraktion entsprach der Methode von Sachse & Bachmann (1969) und zeigte eine nahezu vollst?ndige Extraktion der Glykoalkaloide an (Tabelle 3). Die Methode ist genau und empfindlich wie Tabelle 4 für die Glykoalkaloidwerte mehrerer Proben zeigt. Eine ann?hernde Bestimmung des Glykoalkaloidgehaltes kann durch einen visuellen Vergleich von Proben- und Standardflecken durchgeführt werden. Für diese halbquantitative DC genügt die einfachen-Butanol-Extraktion.

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Résumé Une méthode de détermination quantitative rapide de la solanine et de la chaconine est décrite. La première extraction des glucoalcalo?des par mélange avec le méthanol a été comparée avec l'extraction sous réfrigérant à reflux, selon la méthode de Sachse et Bachmann. Après le traitement des extraits par précipitation, les glucoalcalo?des ont été séparés par chromathographie sur couche mince (TLC) et évalué par fluorodensitométrie directement sur les chromatogrammes. Dans la mesure où aucune différence significative (α=0,05) n'a été trouvée entre les deux méthodes d'extraction (tableau 1), celle demandant le moins de travail a été choisie pour l'extraction de ces substances dans les autres échantillons. Pour gagner du temps sur la méthode de précipitation, nous avons procédé à deux modifications au niveau de l'extraction aun. butanol utilisée par Crabbe & Fryer (1980). La première consistait à dissoudre la résidu sec de l'extraction précédente dans un mélange, en parties égales, den. butanol saturé avec 1% d'ammoniaque et de 1% d'ammoniaque saturé den. butanol. Après séparation des deux phases, la phasen. butanol a été utilisée pour l'essai quantitatif en chromatographie sur couche mince. La seconde modification consistait à dissoudre la résidu sec dans de l'acide acétique dilué et à centrifuger la solution acide. Cette solution clarifiée était alcalisée et l'extraction était faite aun.butanol; l'utilisation d'un solvant saturé étant impossible dans ce cas, un facteur de correction de volume a été déterminé pour len.butanol. Après agitation on conservait 9,5 ml des 10 ml d'origine de la phasen.butanol. Les résultats de ces deux procédés ont été comparés avec ceux obtenus par la méthode de précipitation (tableau 2). Avec la seule extraction aun.butanol la séparation des glucoalcalo?des par chromatographie a été perturbée pour les échantillons ayant une faible teneur en donnant des valeurs trop élevées. L'extraction à l'acide acétique/n.butanol a donné des valeurs égales ou légèrement supérieures à celles de la méthode de précipitation. La séparation des glucoalcalo?des n'a pas été perturbée par les autres composés fluorescents. Les valeurs obtenues par la méthode totale=mélange avec méthanol et extraction à l'acide acétique/n.butanol ont été approximativement les mêmes que celles obtenues par la méthode de Sachse & Bachmann (1969); elles indiquent une presque complète extraction des glucoalcalo?des (tableau 3). La méthode est précise et sensible comme le montrent les valeurs indiquées dans le tableau 4. Une évaluation approximative de la teneur en glucoalcalo?des peut être obtenue par comparaison visuelle entre l'échantillon et des bandes témoins standard. Pour cette chromatographie semi-quantitative la simple extraction aun.butanol est suffisante.

     

Effect of heading date of perennial ryegrass cultivars on tillering and tiller development in spring and summer

Three cultivars (two diploid and one tetraploid) in each of three maturity groups (early, intermediate and late) of perennial ryegrass were sown in 10 m² plots, replicated four times, in Northern Ireland in June 1997 in a study of the effect of heading date on tiller development (including initiation to flower) and turnover of tillers produced at specific times in spring in 1998 and 1999. The plots were harvested seven times in each year. Annual dry‐matter production was similar for all groups in each year. In spring and early summer of both years, tiller density of the diploid cultivars was 1·5 times greater than that of the tetraploid cultivars and the mean tiller density over all swards in June was about 0·40 times greater than that in April. Maximum proportions of reproductive tillers in the early, intermediate and late maturity groups, determined from apical dissections, were found in early April, mid‐May and early June, respectively. Although a high proportion of tillers, which were present when annual observations commenced in spring, was decapitated at the first harvest in the early group, the previous population density was maintained by rapid production of new tillers during May, including those from suppressed tiller buds during reproduction. It is concluded that the relationship between heading date and rate of tiller turnover (including flowering) at specified times in spring is important in sward management throughout the early part of the growing season and should be taken into account in tiller‐based grass growth models.     

甘蔗增糖增产剂对不同甘蔗品种（系）产量和品质的影响

以广西引进和自育的甘蔗品种（系）为试验材料,在甘蔗生长后期喷施甘蔗增糖增产剂的试验结果表明：甘蔗增糖增产剂处理对参试甘蔗各品种（系）的增产作用不明显;而对甘蔗品质有明显影响,能明显提高甘蔗蔗糖分,并能抑制甘蔗早熟品种退糖,降低甘蔗工艺成熟早期的还原糖分,改善蔗汁的品质,同时还一定地提高甘蔗的抗寒能力。     

播期对三江平原主栽水稻品种品质的影响

通过播期试验,对三江平原5个主栽水稻品种的品质性状进行分析。结果表明,播期对整精米率、垩白米率、垩白度、直链淀粉含量、蛋白质含量、食味值均有影响,对糙米率、精米率影响较小。随着播期的推迟,整精米率明显降低,外观品质变劣,且二者呈极显著负相关;直链淀粉含量呈升高趋势,蛋白质含量则呈降低趋势;食味值变化因品种而异。对品质各性状的变异系数进行聚类分析,结果表明,垩白粒率、垩白度受播期影响最大,属于敏感性状;糙米率、精米率、食味值、直链淀粉含量和蛋白质含量受播期影响较小,属于迟钝性状;整精米率受播期影响变异幅度在二者之间。综合而言,早播对5个水稻品种整体品质提升具有正向作用;但从食味值角度出发,早熟品种龙粳31和龙粳46适当晚播可能更有利于口感的改善。     

北方冬麦区小麦品种产量相关性状和幼穗分化特点研究

为了解北方冬麦区小麦产量相关性状和幼穗分化特点,对该麦区10个代表性小麦品种的产量相关性状和幼穗分化进程进行了研究。结果表明,8个产量相关性状在10个品种间存在不同程度的差异;产量与穗数、穗粒数和千粒重间相关系数分别为0.28、0.45和0.08。不同生态区小麦品种间产量潜力差异较小,高产品种（> 9 000 kg·hm^-2）的成穗数均为中等偏多型。品种间幼穗分化进程有明显差异,北部冬麦区和黄淮冬麦区北片品种一般表现为前期发育慢,后期发育快,个别品种的各个时期发育均慢;黄淮冬麦区南片多数品种则表现为各个时期发育都较快,个别品种前期快,中期慢,后期快。对春化和光周期基因不同等位变异检测发现,除了Vrn-D1,10个供试品种在其他已知春化基因和光周期基因座Vrn-A1、Vrn-B1、Vrn-B3和Ppd-D1上含有相同的等位变异。     

The effect of defoliation practice in Western Australia on tiller development of annual ryegrass (Lolium rigidum) and Italian ryegrass (Lolium multiflorum) and its association with forage quality

The effect of defoliation on the vegetative, early reproductive and inflorescence stages of tiller development, changes in the dry‐matter yield of leaf, stem and inflorescence and the associated changes in forage quality was determined on plants of annual ryegrass (Lolium rigidum Gaud.) and Italian ryegrass (L. multiflorum Lam.). The field study comprised seventy‐two plots of 1 m × 2 m, sown with one annual ryegrass and seven Italian ryegrass cultivars with a range of heading dates from early to late; defoliation commenced 6 weeks after germination. During the vegetative stage of growth, plots were defoliated when the tillers had three fully expanded leaves (three‐leaf stage). During the early reproductive stage of growth, to simulate a cut for silage, plots were defoliated 6–7 weeks after 0·10 of the tillers displayed nodal development. The subsequent regrowth was defoliated every 3 weeks. Assessments of changes in tiller density, yield and quality were made in the growth cycle that followed three contrasting cutting treatments during the winter–spring period (from 10 July). In treatment 1, this growth cycle (following closing‐up before a subsequent conservation cut) commenced on 7 August following two defoliations each taken when the tillers were at the three‐leaf stage. In treatment 2, the growth cycle commenced on 16 October following: for early‐maturing cultivars, two cuts at the three‐leaf stage, a cut for silage and an additional regrowth cut; for medium‐maturing cultivars three cuts at the three‐leaf stage and a cut for silage; and late‐maturing cultivars, five cuts at the three‐leaf stage. In treatment 3, defoliation up to 16 October was as for treatment 2, but the growth cycle studied started on 27 November following two additional regrowth cuts for early‐ and medium‐maturing cultivars and cut for silage for the late‐maturing cultivars. Tiller development for all cultivars was classified into three stages; vegetative, early reproductive and inflorescence. In treatment 1, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with maturation of tillers. IVDMD ranged from 0·85 to 0·60 and CP ranged from 200 to less than 100 g kg^–1 dry matter (DM) during the vegetative and inflorescence stages respectively. This large reduction in forage quality was due to an increase in the proportion of stem, inflorescence and dead material, combined with a reduction in the IVDMD and CP content of the stem. A high level of forage quality was retained for longer with later‐maturing cultivars, and/or when vegetative tillers were initiated from the defoliation of early reproductive tillers (treatments 2 and 3). However, 15 weeks after the closing‐up date in treatment 1, defoliation significantly reduced the density of inflorescences with means (±pooled s.e_m.) of 1560, 1178 and 299 ± 108 tillers m^–2, and DM yield of inflorescence with means of 3·0, 0·6 and 0·1 ± 0·15 t ha^–1 for treatments 1, 2 and 3 respectively. This study supports the recommendation that annual and Italian ryegrass cultivars should be classified according to maturity date based on the onset of inflorescence emergence, and that the judicious defoliation of early reproductive tillers can be used to promote the initiation of new vegetative tillers which in turn will retain forage quality for longer.