Spike Traits Research Articles

Allocation of Photosynthates and Grain Growth of Two Wheat Cultivars with Different Potential Grain Growth in Response to Pre‐ and Post‐anthesis Shading

AbstractGrain yield in wheat is dependent on photosynthate production and allocation. Light intensity is one of the main factors affecting photosynthate production and allocation, and grain yield. This study was conducted to determine whether cultivars varying in grain number per spike and grain weight respond differently to pre‐anthesis shading (PRE) and post‐anthesis shading (POST), and to characterize the responses in production and allocation of photosynthate, yield and yield components, and spike traits. Both PRE and POST caused a decrease in both dry matter (DM) accumulation and allocation to grain. Cultivar Lumai 22, which has a large spike and large grains, was more sensitive to either PRE or POST. PRE reduced photosynthate production and partitioning to the spike in Lumai 22 at anthesis. In contrast, PRE had little influence on these parameters in the small‐spike, small‐grain cultivar Yannong 15. POST reduced the partitioning to the grain, especially in Lumai 22, for which marked reductions in biomass and grain yield were found for both the PRE and POST treatments. Changes in yield components attributable to shading varied with cultivars. The number of spikes m−2 was not affected by either PRE or POST. Lumai 22 was more seriously affected by shading than Yannong 15 in terms of grain number per spike and weight per grain. The decreases in grain number or weight per spikelet in both the PRE and POST treatments took place mainly in the upper and basal spikelets, especially in Lumai 22. We concluded that the adaptability of the small‐spike, small‐grain cultivar Yannong 15 to either PRE or POST was much greater than that of the large‐spike, large‐grain cultivar Lumai 22 in terms of many characteristics closely related to grain yield. Hence, we suggest that, in areas where low light intensity often occurs, the small‐spike, small‐grain cultivar would be more likely to produce high, stable grain yields.

Seed and spike traits from remnant populations of Cenchrus ciliaris L. in South Tunisia: high distinctiveness, no ecotypes

In South Tunisia, as part of a native seed production program, a collection of 52 accessions ofCenchrus ciliaris was assessed for 12 different traits related to seed and spike. Possible relations between these, eco-geographic origin, and 4 adaptive traits of agronomical value were investigated. We could not establish reliable correlations between traits, nor between traits and eco-geographic origin. However, accessions were very distinct and homogeneous. Our data suggest that native seed production can consider South Tunisia as a single source and target region, but should define sound criteria to select a limited number of accessions for multiplication.

Tiller Development of Winter Type Wheat Iwainodaichi Sown Early in the Southwestern Part of Japan.

暖地のコムギ作における収穫の早期化を実現するための基礎的知見を得るため, 早播きした秋播性コムギの分げつの発育の特徴を明らかにした. 秋播性程度の高いイワイノダイチ(秋播性程度IV)と対照品種のチクゴイズミ(同I～II)を, 1998年の10月26日(極早播き), 11月5日(早播き), 11月24日(標準播き)に播種し, 栽培した. 単位面積当たりの最高茎数は, イワイノダイチがチクゴイズミより著しく多かった. 単位面積当たりの穂数は, イワイノダイチがチクゴイズミよりやや多く, また播種期が遅いほどやや多かった. 個体を対象として分げつの発育過程をみると, いずれの播種期や品種においても分げつは主茎の出葉にともなってT1, T2, T3およびその同伸分げつのT1P, T4およびその同伸分げつのT11とT2Pの順に規則的に出現した. イワイノダイチはチクゴイズミよりT4, T11, T2Pなどの高位・高次の分げつの出現率が高かったが, これらの分げつは無効化することが多かった. 有効分げつでは出葉速度は主茎とほぼ同じであったが, 無効分げつでは出葉速度は次第に低下し, 出葉の停止, 枯死に至った. そこで, 無効分げつは, その出葉速度が主茎の半分以下となった時点で無効化したとして, 個体当たりの分げつ数の推移をみたところ, 早播きのイワイノダイチの分げつ数が最大となる時期は早播きのチクゴイズミより遅く, 標準播きのイワイノダイチ, チクゴイズミより早かった. このような分げつ数の推移は幼穂の発育と密接に関連していることが示唆された.

Chromosomal location of genes for supernumerary spikelet in tetraploid wheat

The supernumerary spikelet (SS) trait of durum wheat (Triticum turgidum L.), including the ramified and four-rowed spike traits, is characterized by an increased number of spikelets per spike. Chromosomal location of the SS gene(s) was determined by crossing the ramified spike line PI349056 to the set of 'Langdon' D-genome disomic substitution lines. Double monosomic F1 plants were backcrossed to PI349056 and the testcross F1 plants were classified for chromosome pairing and spike type. Segregation for spike type was observed in the testcross F2. Data indicated that the major SS gene was located on chromosome 2A. Subsequent crosses with the 'Langdon' 2A telosomics indicated that the major SS gene was located on the short arm of chromosome 2A. Segregation of the testcross F2 indicated that a minor SS gene was located on chromosome 2B. Results also indicated that inhibitors of SS may be located on the D-genome chromosomes and an additional experiment was designed to test this hypothesis. Eight D-genome monosomic addition lines were developed by backcrossing PI349056 from one to three times to plants containing D-genome univalents. The test populations contained two cytological types of plants, disomics having 14 pairs of durum chromosomes and D-genome monosomic additions having 14 pairs of durum chromosomes plus a D-genome monosome. Comparison of these two types of plants indicated that chromosome 2D (from 'Chinese Spring' wheat) had a strong inhibitor of SS expression.Key words: Triticum, branched spike, ramified spike, four-rowed spike, cytogenetics.