The transfer of a gene for glutinous endosperm to Oryza glaberrima Steud. From a japonica variety of O. sativa L.

Summary In common rice, Oryza sativa L. (n=12), the gene Am for non-glutinous is dominant over the gene am for glutinous. In African rice, O. glaberrima Steud. (n=12), no spontaneous glutinous strain has been found, but recently a glutinous strain of glaberrima was induced by EMS-treatment.The interspecific cytoplasm substitution line with sativa cytoplasm and glaberrima nucleus is male sterile. It has been confirmed that the complete restoration of pollen fertility in this male sterile line is attributed to a single dominant nuclear gene Rf _j.Trial to transfer gene am from sativa to glaberrima was commenced with backcrosses of the F₁ hybrid (glutinous sativa cv. Iwai-mochi × glaberrima ) to glaberrima type plants of the substitution line homozygous for Rf _j,using the latter as the pollen parent. At the B₁ step, highly fertile glaberrima type Am/am plants were obtained. Thereafter plants of this type were backcrossed to normal glaberrima as the recurrent pollen parent to complete the nuclear substitution. It was confirmed that the EMS-induced glutinous character of glaberrima was a monogenic recessive and that the same gene controls the expression of glutinous character in the different rice species, sativa and glaberrima.     

Application of Functional Markers to Identify Genes for Bacterial Blight Resistance in Oryza rufipogon

Field resistances of nine accessions of common wild rice (Oryza rufipogon Griff.) and one rice variety (IR24) were evaluated by using nine strains of bacterial blight pathogen (Xanthomonas oryzae pv. oryzae) from the Philippines. IR24 was highly susceptible to all the strains, and six common wild rice accessions resisted all the nine strains, with a resistance frequency of 67%. The accessions Yulin and Wanning were only susceptible to PXO280 and PXO71, respectively. The accession Gaozhou was susceptible to the three strains PXO79, PXO99 and PXO339, whereas resistant to the other six strains. It could be concluded that there is at least one resistance gene in each common wild rice accession. The functional markers of the genes xa5, xa13, Xa21 and Xa27 were used to detect the presence of these resistance genes in the nine tested wild rice accessions, and it was found that four wild rice accessions contained heterozygous xa13. Among the nine common wild rice accessions, five were homozygous for Xa27 and three homozygous for xa27, and the accession Laibin contained neither xa27 nor Xa27. In addition, there were no xa5 and Xa21 in all of these accessions.     

Development of new sources of cytoplasmic male-sterile lines in rice

Two male-sterile lines, KalashreeA and PadminiA, with a Miz.21 cytoplasm source were developed through indica/indica hybridization followed by repeated backcrossing with their respective recurrent male parents (Kalashree and Padmini) up to the BC₆ generation. These two cytoplasmic male-sterile lines are suitable for use in the development of hybrids for lowland situations owing to their intermediate to semi-tall stature, late flowering duration, good grain quality and easy fertility restoration ability.     

Variation in cooking and eating quality traits in Japanese rice germplasm accessions

The eating quality of cooked rice is important and determines its market price and consumer acceptance. To comprehensively describe the variation of eating quality in 183 rice germplasm accessions, we evaluated 33 eating-quality traits including amylose and protein contents, pasting properties of rice flour, and texture of cooked rice grains. All eating-quality traits varied widely in the germplasm accessions. Principal-components analysis (PCA) revealed that allelic differences in the Wx gene explained the largest proportion of phenotypic variation of the eating-quality traits. In 146 accessions of non-glutinous temperate japonica rice, PCA revealed that protein content and surface texture of the cooked rice grains significantly explained phenotypic variations of the eating-quality traits. An allelic difference based on simple sequence repeats, which was located near a quantitative trait locus (QTL) on the short arm of chromosome 3, was associated with differences in the eating quality of non-glutinous temperate japonica rice. These results suggest that eating quality is controlled by genetic factors, including the Wx gene and the QTL on chromosome 3, in Japanese rice accessions. These genetic factors have been consciously selected for eating quality during rice breeding programs in Japan.     

水稻苗期生长特性的遗传剖析

 以1个水稻重组自交系为作图群体进行盆栽试验，分别在播种后第14、24、34和44天进行第1、2、3和第4次取样，考察秧苗苗高和干物重以及播种前所用种子的千粒重。结合1张高密度的遗传图谱，对性状进行复合区间作图，分别检测到控制秧苗干物重、苗高和种子千粒重的主效应QTL 6、14和3个。其中，位于3号染色体RM148-RM85区段的QTL qGC-3-3同时影响第4期干物重和第1、3和4期苗高，且其对苗高的效应呈逐期递增的趋势。与qGC-3-3相反，位于5号染色体RM163-RM161区段的QTL qGC-5 同时影响第1～3期的干物重和苗高，但其效应由强趋弱。在第1～4期中，秧苗干物重与苗高的相关系数分别为0.60～.70，为极显著（P<0.01）正相关。秧苗干物重和苗高与种子千粒重的相关性均呈逐期递减的趋势、以至于到后期相关性较弱或不显著。QTL定位结果表明，对种子千粒重效应最大的QTL正是上述5号染色体上的qGC-5，该QTL对这3个相关性状的效应方向均一致，但对秧苗干物重和苗高的效应大小是逐期递减。将本研究中定位到的QTL与已报道的利用同一定位群体所检测到的籽粒产量性状QTL相比较，发现有的QTL（如3号染色体上的QTL qGC-3-1和qGC-3-3）尽管在水稻生育早期的效应较小，但其效应随着生育进程的发展而逐期递增，且加性效应的方向在全生育期一致；有的QTL（如5号染色体上的qGC-5）在水稻生育早期的效应相对较大，但其效应逐期减弱，以至于对生育后期的生长发育和产量性状没有直接影响或影响很小。这些QTL的表达具有较强的时期特异性。     

共生性广谱生物固氮菌剂在红黄壤水稻上的应用效应研究

将共生性广谱生物固氮菌剂G肥应用于红黄壤水稻上,对水稻的一些生理活性、水稻的衰老、土壤肥力变化、稻米品质和产量进行了研究.结果表明,施用G肥能有效地促进水稻生长,稻株出叶速度加快,分蘖速度快,成穗率提高:叶片叶绿素含量提高,根系活力增强,尤其是在灌浆成熟期仍保持较高的叶绿素含量和根系活力,剑叶SOD、POD等保护酶类活性提高、MDA含量降低,对于提高光合速率、争取高产优质是极为有利的.结果还表明,施用G肥与常规栽培比,对稻米品质无明显影响.此外,施用G肥可减少氮肥20%,改善水稻经济性状,提高产量,直接经济效益明显:施用G肥可有效缓解偏施氮肥引起的土壤酸化,提高土壤全氮含量和有机质含量,对红黄壤的可持续开发利用具有重要的意义.     

一个控制水稻叶色白化转绿及多分蘖矮杆性状基因hw-1(t)的鉴定

通过空间诱变从光身稻品种Francis的M₂群体中发现一株叶色白化转绿、多分蘖矮秆突变体hfa-1。hfa-1在三叶期之前完全白化,随后转绿。白化转绿表型受生长发育和温度调控。亚细胞结构观察发现hfa-1叶绿体发育异常抑制叶绿素合成,造成光合效率降低,产生白化表型。hfa-1的多分蘖表型是由于高节位分蘖芽激活所致,初步鉴定与苗期叶片IAA (吲哚乙酸)含量无关。hfa-1的矮生性则由节间长度缩短所致,与苗期GA (赤霉素)的合成和信号传导无关。遗传分析表明hfa-1的白化转绿、多分蘖矮秆表型受单隐性核基因hw-1(t)控制。利用hfa-1与粳稻品种02428杂交获得的F₂群体将hw-1(t)定位在水稻第4染色体长臂上两个InDel标记HW27和HW7间46.9 kb的物理距离内,该区域有13个阅读框架,其中LOC_Os04g57320编码IMMUTANTS蛋白,推测为hw-1(t)的候选基因。     

中国粳稻地方种资源核心样品的构建方法研究

以《中国稻种资源目录》中的16 791份中国粳稻地方种为材料,根据完全随机、变种类型（丁颖分类法）下随机和系统聚类3种取样方法和4种核心样品规模（12.5%、10%、7.5%和5%）设计12个核心样品,以8个编目性状的平均数变幅、方差和变异系数加以评价。结果表明：（1）变种类型下系统聚类取样方法是构建中国粳稻地方种资源核心样品的适宜方法;（2）样品规模5%的核心样品可以有效地代表中国粳稻地方种资源的总体样品。     

Effects of twice harvesting on total dry matter yield of rice

We examined the effect of twice harvesting of forage rice with the first harvest at the full heading stage on total dry matter yield in the cultivars Taporuri, Mohretsu, and Hinohikari and in line Saikaishi 253 in southwestern Japan. Taporuri produced the highest total dry matter yield, with a value 60% higher than that of Hinohikari. The first crop of Taporuri had a longer duration of vegetative growth than those of Mohretsu and Hinohikari, and had the highest dry matter yield because of its greater weight per tiller than Hinohikari and its more tillers per square meter than Saikaishi 253, which had a similar duration of vegetative growth. The second crops of Mohretsu, Taporuri, and Saikaishi 253 had longer vegetative growth and higher dry matter yields than Hinohikari. Dry matter yields of both crops were closely related to the duration of vegetative growth and the weight per tiller, but not to tillers per square meter. These results suggest that cultivars with a long duration of vegetative growth, high weight per tiller, and adequate tillers per square meter can produce high dry matter yield in both crops. There was a significant interaction (P < 0.05) in total dry matter yield between cultivar or line and cultivation type. The total dry matter yield of Taporuri in twice harvesting was about 10% higher than that in once harvesting, whereas that of Hinohikari was about 10% lower. The suitability for twice harvesting ([total dry matter yield in twice harvesting]/[total dry matter yield in once harvesting]) was significantly positively correlated (r = 0.875) with the increase in dry weight before the full heading stage, but significantly negatively correlated (r = −0.903) with the increase in dry weight between full heading and the yellow ripe stage. Thus, cultivars with a high increase in dry weight before full heading appear to be more suitable for twice harvesting than those with a high increase between full heading and the yellow ripe stage. In addition, our study showed that twice harvesting can prevent lodging in Taporuri, thereby increasing the suitability of this cultivar as a forage rice. Our results suggest that twice harvesting can be performed in southwestern Japan and warmer regions.     

水稻黑条矮缩病抗性评价方法及抗性资源筛选

水稻黑条矮缩病是水稻主要病毒病害之一。目前由于缺乏规模、高效的黑条矮缩病抗性鉴定体系,制约了抗黑条矮缩病水稻资源的发掘,限制了抗黑条矮缩病的育种进程和基础研究。本研究通过分析水稻黑条矮缩病田间鉴定所需灰飞虱的有效接种密度、带毒率及播期等,提出水稻黑条矮缩病田间鉴定有效接种的灰飞虱密度在800万头 hm^-2左右较为合理,而带毒率应不低于5%。并进一步对现有黑条矮缩病人工接种鉴定的循回期、接种虫量、接种时间及虫龄等进行了优化。利用上述鉴定体系,2010年对来源于20个国家的共1240份水稻种质进行黑条矮缩病田间鉴定,初步获得发病率低于10%的品种34个;2011、2012连续两年对该34个品种进行多年多点重复抗性鉴定,发现来自东南亚地区的3个品种Kanyakumari 29、Madurai 25和Vietnam 160连续3年发病率均低于10%,表现较高的黑条矮缩病的抗性。进一步分期播种鉴定的结果表明,Kanyakumari29在3个播期、3个鉴定点的发病率均低于12%,而Madurai 25和Vietnam 160发病率均低于9%。此外,在人工接种条件下Kanyakumari 29、Madurai 25和Vietnam 160的发病率均低于9%。因此,多年多点田间鉴定和人工室内接种鉴定的结果均表明,Kanyakumari 29、Madurai 25和Vietnam 160稳定、高抗黑条矮缩病。综上所述,本研究建立的田间鉴定与室内鉴定相结合的黑条矮缩病鉴定体系准确、可靠,可用于黑条矮缩病的大规模鉴定,该体系的建立及高抗黑条矮缩病水稻资源的发掘为水稻抗黑条矮缩病基因的鉴定及育种利用提供了重要的方法和材料基础。