Transpiration response of two bread wheat lines differing in drought resilience and their backcross parent under dry-down conditions

Improving wheat productivity in drylands largely depends on how plants manage limited water resources. Using fraction of transpirable soil water threshold (FTSW_Th) and drought stress response function, we characterized the water conservation traits of two wheat multiple synthetic derivative lines (MSD53 and MSD345) which both contain introgressed segments from Aegilops tauschii but differ in drought resilience. The lines and their backcross parent, ‘Norin 61’, were subjected to dry-down conditions. MSD53 had a higher FTSW_Th for transpiration decrease than ‘Norin 61’ and MSD345. In terms of drought stress response function, MSD53 had the lowest threshold suction, suggesting a lower drought resilience capacity compared with MSD345. However, MSD53 exhibited an effective-water-use trait whereas MSD345 exhibited a water-saving trait under dry-down conditions. These results are consistent with the reported higher yield of MSD53 in comparison with MSD345 under drought stress in Sudan, and demonstrate that high FTSW_Th supports effective water use for improved agricultural productivity in drylands. The differences in water conservation traits between the two MSD lines may be attributed to variation in introgressed segments, which can be further explored for drought resilience breeding.     

Applicability of Aegilops tauschii drought tolerance traits to breeding of hexaploid wheat

Few genes are available to develop drought-tolerant bread wheat (Triticum aestivum L.) cultivars. One way to enhance bread wheat’s genetic diversity would be to take advantage of the diversity of wild species by creating synthetic hexaploid wheat (SW) with the genomic constitution of bread wheat. In this study, we compared the expression of traits encoded at different ploidy levels and evaluated the applicability of Aegilops tauschii drought-related traits using 33 Ae. tauschii accessions along with their corresponding SW lines under well-watered and drought conditions. We found wide variation in Ae. tauschii, and even wider variation in the SW lines. Some SW lines were more drought-tolerant than the standard cultivar Cham 6. Aegilops tauschii from some regions gave better performing SW lines. The traits of Ae. tauschii were not significantly correlated with their corresponding SW lines, indicating that the traits expressed in wild diploid relatives of wheat may not predict the traits that will be expressed in SW lines derived from them. We suggest that, regardless of the adaptability and performance of the Ae. tauschii under drought, production of SW could probably result in genotypes with enhanced trait expression due to gene interactions, and that the traits of the synthetic should be evaluated in hexaploid level.     

小麦F2:3家系抗旱相关性状的遗传变异分析

摘要：在水地和旱地两种环境条件下种植以敏感型品种偃展2号和抗旱型品种石4185为亲本构建的402个F2:3家系群体,应用该群体在水地和旱地两种环境条件下研究了株高、穗长、穗茎节长、旗叶长、旗叶宽、穗数、小穗数、穗粒数、穗粒重9个数量性状的遗传特点。结果表明：两种环境条件下,F2:3家系各性状分离明显, 且基本符合正态分布, 表现为数量性状遗传特点, 是一个较为理想的QTL作图群体。     

Assessment of genetic diversity in bread wheat genotypes for tolerance to drought using AFLPs and agronomic traits

Moisture stress greatly limits the productivity of wheat in many wheat-growing regions of the world. Knowledge of the degree of genetic diversity among parental materials for key selection traits will facilitate the development of high yielding, stress tolerant wheat cultivars. The objectives of this study were to: (i) use amplified fragment length polymorphisms (AFLPs) to assess genetic diversity among bread wheat lines and cultivars with different responses to drought stress in two distinct environments and, (ii) compare genetic diversity estimated by AFLPs with diversity evaluated on agronomic performance under drought stress. Twenty-eight genotypes, 14 from Iran and 14 developed or obtained by CIMMYT, were evaluated in the study. Phenotypic data on the 14 Iranian lines were obtained in Iran, and data on the 14 CIMMYT lines were collected in Mexico. Ten AFLP primer pairs detected 335 polymorphic bands among the 28 cultivars. At the 5th fusion level of the resulting dendrogram, 6 genotype clusters were identified. Thirteen of the 14 CIMMYT genotypes grouped into one cluster while 4 of the remaining groups were comprised only of Iranian genotypes. When the agronomic performance of the Iranian materials was compared with the AFLP diversity analysis, 5 of the 6 drought susceptible genotypes clustered together in the agronomic dendrogram, and were located in the same cluster in the AFLP dendrogram. However, the drought tolerant Iranian materials did not show the same degree of relationship. The CIMMYT materials did not demonstrate a significant association between agronomic performance and genetic diversity determined using AFLPs. Clearly these data show that there are genotypes with similar agronomic performance and different genetic constitutions in this study that can be combined in a breeding program to potentially improve tolerance to drought stress.     

Marker‐assisted backcross breeding for improvement of drought tolerance in bread wheat (Triticum aestivum L. em Thell)

Drought stress is presently a major productivity limiting factor in wheat. This study developed five wheat lines with inbuilt tolerance to drought stress using marker‐assisted backcross breeding (MABB) approach employing three linked quantitative trait loci (QTLs) in an initial population of 516 BC₁F₁ plants. The high‐yielding wheat cultivar ‘HD2733’ grown over last few years extensively in the eastern plains of India is largely sensitive to drought and is used as the recurrent parent. ‘HI1500’ released for water‐limiting conditions and carrying drought‐tolerant QTLs was used as donor parent. MABB lines were advanced using foreground and background selection, coupled with stringent phenotyping. We identified 29 lines that were homozygous for targeted QTLs in different combinations with background recovery range of 89.2%–95.4%. Further evaluation of selected lines for physiological traits and distinctness, uniformity and stability (DUS) characters under rainfed condition identified five potential varieties for national varietal evaluation programme in the zone. The report is first of its kind in implementing known QTLs for the development of drought‐tolerant wheat lines through MABB approach.     

Genetic variability,heritability and correlation among agronomic and disease resistance traits in a diversity panel and elite breeding material of spelt wheat

Spelt wheat (Triticum spelta L.) is an old‐world crop that has attracted increased attention since the 1970s accompanied by a constant increase in spelt production. Our objectives were to (i) study the genetic variability and heritability of important agronomic traits and (ii) examine the correlation among these traits for an efficient design of spelt breeding schemes. To this end, we compared a diversity panel of 150 old and new spelt varieties with current elite‐breeding material. Phenotypic data were recorded at multiple locations for yield, plant height, lodging, heading time, number of spikelets, ear snapping and susceptibility to powdery mildew, brown rust and Septoria tritici blotch. We observed highly significant genetic variances for almost all traits in both germplasm sets. Heritability estimates ranged from 0.23 for Septoria tritici blotch to 0.97 for plant height. A significant correlation between yield and plant height of ?0.56 as well as yield and lodging of ?0.39 was determined but no other correlation of yield with any of the examined traits. Thus, pedigree selection with early generation screenings on plant height and lodging can be recommended for further spelt improvement.     

Genetic resources of wild cereals in Israel and vicinity. I. Phenotypic variation within and between populations of wild wheat,Triticum dicoccoides

Summary Populations of wild emmer wheat, Triticum dicoccoides, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1982) and disease resistance polymorphisms (Moseman et al., 1983a, 1983b; Nevo et al., 1984a, 1984b), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, biomass and yield variables. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric (Acedat Farm, and Sede Boqer, in the northern Negev desert). The experimental design involved 12 population quadrangles at Avedat Farm in 1980, and rows of randomized genotypes of five populations in both Haifa and Sede Boqer in 1981 and 1982.The results indicate that the characters studied are partly genetically determined. Striking genetic variation was found between and, at least in some characters, also within populations in each site, whereas remarkable environmental variation including genetic-environmental interaction was found between the mesic and the xeric sites. We conclude that natural populations of wild emmer wheat in Israel vary not only in genetic polymorphisms of allozymes and disease resistance, but also in quantitative traits of agronomic importance. These traits are economically significant and should be conserved and utilized in wheat crop improvement.     

Ear:stem ratios in breeding populations of wheat: significance for yield improvement

Earlier studies showed that the ratio of the weight of the wheat ear to stem at anthesis (ear:stem ratio) may give a better indication of potential yield than harvest index because it is determined early in the life cycle and is not affected by post anthesis stress. These studies concluded that selection for high ear:stem ratio at anthesis may lead to further improvement in grain yield of wheat. The present work was undertaken in the field to identify lines varying in ear:stem ratio in breeding populations and to study its implications for yield improvement.At anthesis stem length, ear length, tiller number, dry weight of stem and ear and ear:stem ratio were measured in 14 crosses on F₂ single plants and F₂ derived lines grown in the F₃, F₄, and F₅ at three locations in Western Australia over four seasons. In addition, biomass, grain yield and yield components were measured on selected crosses at two locations on F₂ derived lines grown in the F₄ and F₅. There was a considerable range of ear:stem ratio between and within the crosses studied. Although ear:stem ratio was strongly correlated with stem length, there was substantial variation within stem length classes. Ear:stem ratio had a high mean broad sense heritability (82%), whereas HI, grain yield and above ground biomass had lower heritabilities, 68, 55 and 35% respectively. Ear:stem ratio was strongly correlated between generations and sites indicating stability of this character. Ear:stem ratio had a significant positive correlation with grain yield, HI, grains per ear and per m². The correlation of grain yield with HI was equal or slightly higher than that of grain yield with ear:stem ratio.Ear:stem ratio offers promise as a predictor of HI and yield potential where post-anthesis moisture stress can influence HI. Ear:stem ratio measurement is unlikely to be adopted for selection purposes in routine breeding programs, as it is laborious and time consuming. However, ear:stem ratio could be used to identify superior parental genotypes and early generation selections from special crosses in terms of its ability to partition assimilate.     

Genetic variation for resistance to Fusarium head blight in bread wheat

Summary During a four year period, a total of 258 winter and spring wheat genotypes were evaluated for resistance to head blight after inoculation with Fusarium culmorum strain IPO 39-01. It was concluded that genetic variation for resistance is very large. Spring wheat genotypes which had been reported to be resistant to head blight caused by Fusarium graminearum were also resistant to F. culmorum. The resistant germplasm was divided into three gene pools: winter wheats from Eastern Europe, spring wheats from China/Japan and spring wheats from Brazil. In 32 winter wheat genotypes in 1987, and 54 winter wheat genotypes in 1989, the percentage yield reduction depended on the square root of percentage head blight with an average regression coefficient of 6.6. Heritability estimates indicated that for selection for Fusarium head blight resistance, visually assessed head blight was a better selection criterion than yield reduction.     

Genetic variation for tolerance or resistance to barley yellow dwarf virus in durum wheat

Summary One durum wheat line (Triticum durum), cv. 82PCD476, with useful BYDV tolerance or resistance, was singled out of 5 152 lines evaluated between 1979 and 1986. A few other lines such as cv. Boohai and cv. 12th IDSN 227, slightly inferior to cv. 82PCD476, also showed some value. With an hybrid of cv. 12th IDSN227 with the susceptible cv. 84PCY-S531, broad-sense heritability values of 0.37–0.41 were obtained for symptoms and a heritability value of 0.55 was obtained for the total weight of spikes. The weight of spikes was considered as a good indicator of wheat tolerance to BYDV. Although BYDV resistance or tolerance genes are not very common in durum wheat, sources of heritable resistance could be found. However, the resistance ofT. aestivum to BYDV was superior to the one found inT. durum.Cintribution no. 323     

小麦K型不育系恢复基因近等基因系农艺性状的遗传差异分析

摘 要：对近等基因系进行遗传背景检测,有利于选育高质量的近等基因系材料。试验以17个小麦K型不育系恢复基因的近等基因系（N1-N17）和轮回亲本不育系豫麦3号为材料,通过调查这些材料的株高、成穗数、旗叶长、旗叶宽、倒二叶长、脖长、倒一节长、倒二节长、穗长、小穗数等10个农艺性状,对恢复基因恢复基因近等基因系的农艺性状进行了差异比较和聚类分析。结果表明,连续回交5代后,回交后代与轮回亲本在形态性状上表现出较高的一致性,其中N14、 N1 、N7 、N16 和N15与不育系豫麦3号的性状差异较小,在欧氏距离为5.2处把它们聚在同一类,但从各性状的变异系数看,N7和N15自身的变异较大,所以N14、 N1和N16 与不育系豫麦3号具有较好的近等性。     

Location of genes for high grain protein percentage and other quantitative traits in wild wheat Triticum turgidum var. dicoccoides

Summary The genetic control of grain protein percentage (GPP) in the wild tetraploid wheat, Triticum turgidum var. dicoccoides, was determined by crossing four accessions of this taxonomic variety with durum cultivar Inbar, and analyzing the parents, F₁ and F₂ populations. Reciprocal crosses indicated no cytoplasmic effect on GPP. The F₂ variation was continuous in all crosses, showing no transgressive segregation. However, crosses between different accessions of var. dicoccoides showed transgressive segregation indicating the presence of different genes for high GPP in these accessions. Grain protein percentage was mostly codominant with high GPP, showing either no dominance, or a weak dominance. Heritability coefficients (broad sense) ranged from 0.30 to 0.53. Correlation coefficients between GPP and yield components were usually significantly negative, with the exception of the number of spikelets per spike, and in some crosses, grain weight.The number and chromosomal location of genes coding for high GPP were determined by the association between GPP and 27 markers (23 morphological and 4 biochemical markers). For this purpose, the genetic control of these markers, their linkage groups and chromosomal location were studied. At least four loci for high GPP that segregated in the F₂ populations are suggested: one on chromosome arm 1AS, marked by the black glume gene (Bg); one on 1BS, marked by the HMW gliadin locus Gli-B1; one on group 5, marked by the genes for beaked glume (Bkg) and toothed palea (Tp); and one on group 7, marked by the kinky neck gene (Kn). The relationship between GPP and several yield components was studied in a similar manner. In general, loci of markers that correlated positively with high GPP were not correlated with a decrease in yield components. Moreover, several loci of var. dicoccoides were associated with an increase in yield components.The utilization of markers for chromosomal location of genes coding for quantitative traits is compared to the technique of aneuploid analysis, commonly used in wheat. The significance of the above findings for breeding is discussed.