Contribution to yield of cereals has traditionally been studied using yield and various yield components, thus neglecting the role of other organs such as ear awns and flag leaf. Here, we studied the effects of genotypes on the photosynthetic activity of the flag leaf blade and the ear awns of spring wheat. The parameters related to the photosynthetic activity were analyzed in relation to the grain yield and various yield components at maturity. In the present study, ten wheat varieties/lines were tested to find out the effects of flag leaf and ear awns detachment on grain yield. There was much genetic variability among different varieties/lines for different traits. Awns detachment exhibited less effect on yield and yield related characters as compared to flag leaf detachment, while detachment of both had more significant effects than individual treatment. Flag leaf area and some other components showed positive and significant correlation with grain yield. Which suggested that flag leaf + awns might be used a morphological marker, while selecting wheat varieties/lines for good photosynthetic activity and high yield.
. H., Whittington, W. J. (1973): Genotypic differences in flagleafarea and their contribution to grain yield in wheat. Euphytica , 22 , 600-606.
Genotypic differences in flagleafarea and their contribution to grain yield
The experimental material comprised three crosses, namely Cocorit 71 × A-9-30-1, HI 8062 × JNK-4W-128 and Raj 911 × DWL 5002, generated from six diverse parents. Twelve populations of each of these three crosses revealed that sufficient genetic variation was recorded among generations for all the traits in three crosses. The results of a correlation study demonstrated that the grain yield per plant was significantly and positively associated with peduncle area and flag leaf area in the cross Cocorit 71 × A-9-30-1. However, the spike area had poor correlation with grain yield. In the cross HI 8062 × JNK-4W-128, grain yield per plant was positively associated with peduncle area and spike area, whereas flag leaf area showed a positive but weak association with grain yield. In the cross Raj 911 × DWL 5002, grain yield per plant was positively associated with all three physiological traits studied, indicating that improvement in grain yield may be made by these traits in this material. Peduncle area appeared to be the most important trait in the present study because of its association with grain yield in all three crosses. Although flag leaf area and spike area showed a positive association with grain yield in all three crosses, their relative magnitudes and significance changed from one cross to the other. Correlation studies revealed that selection for peduncle area would lead to high yield in durum wheat. However, due consideration should also be given to flag leaf area and spike area during the selection of plants for further tangible advances in grain yield in durum owing to their positive association with grain yield.
The genetics of yield and related traits was studied in barley (
L.) by means of 10 × 10 half-diallel progenies (F
) at three sowing dates. An additive-dominance model fitted only for flag leaf area, spike length and 1000-grain weight at different sowing dates. Both additive (D) and dominance components (H
) were significant for all the traits studied, indicating the preponderance of dominance components in controlling the inheritance for these traits. The value of (H
indicated over-dominance for all the traits except for flag leaf area. Values of ‘F’ indicated an excess of dominant alleles in the parents for all traits except for flag leaf area. The environmental component ‘E’ was significant for all traits. The ratio of H
indicated the symmetrical distribution of genes for all the traits studied. The value of h
was less than one for all traits except for spike length, suggesting that a dominant gene was involved in controlling the inheritance of spike length, whereas multiple genes controlled the inheritance of the remaining traits. The heritability estimates were relatively moderate for flag leaf area and 1000-grain weight, but low for all other traits. However, epistatic interactions had an important role in the expression of other traits. Breeding methods such as bi-parental mating in early segregating generations or diallel selective mating may be advantageous to combine important yield component characters for a tangible advance in six-rowed barley.
Authors:S. Gupta, R. Yadav, K.B. Gaikwad, A. Arora, A. Kumar, A. Kushwah, and N.K. Bainsla
Physiological breeding complementing the conventional approach is increasingly being explored in wheat in view of stagnating annual genetic yield gain. Designing improved plant types required knowledge about physiological traits associated with yield gain in the past. Fourteen wheat varieties including 12 historically important and popular (mega) wheat cultivars and two recently registered varieties were observed for various physiological traits for two years. Both breeding period and genotypes within breeding period accounted for significant differences for most of the physiological traits. Regression analysis indicated curvilinear trend for leaf area index (LAI), flag leaf area, and root length and root weight. Near perfect leaf area index (LAI 5.94) with semi-erect leaves and higher flag leaf area was observed in all time mega variety HD 2967 indicated the importance of plant architecture and crop canopy in yield maximization. Linear declining trend was observed for coleoptile length, number of stomata per cm2 and flag leaf length. Increasing trend for total chlorophyll content and normalized difference for vegetative indices (NDVI) at both vegetative and flowering stage indicated the importance of leaf greenness in yield improvement. Root length has continuously declined except for the latest released varieties, however no such trend was observed for root weight. We propose that grain yield stabilization at still higher level can be achieved by increasing photosynthetic capacity, optimizing the crop canopy slightly less than the optimum, and better partitioning to grain yield through directed physiological based breeding.
Wheat is an important source of staple food and has a major role at human nutrition and it is essential to know the relationships between yield and its components in wheat breeding programs. In the examined characteristics, positive and the expression significant correlation were found statistically between the flag leaf area, germination in mannitol, survival after desiccation and number of tillers per plant with grain yield. Negative and significant relationships were determined statistically between the plant height, water loss of excised leaves, root length and root depth with grain yield. Path coefficient revealed that number of tillers per plant (9.166) and root depth (0.2675) had the highest positive direct effects on grain yield. In addition water loss of excised leaves (−9.057) and survival after desiccation (−0.449) have highest negative direct effect on grain yield. The improvement in grain yield will be efficient if the selection is based on the number of tillers per plant, root depth and flag leaf area under drought conditions. Comparatively high genetic variability was found in grain yield, flag leaf area and tillers per plant. Number of tillers per plant had direct and marked effect and majority of the traits affected grain yield through it.
The investigation was concerned with the effects of water stress on the yield and yield components of wheat grown under rainfed conditions in Rawalakot, Pakistan. A pot experiment was conducted with four wheat genotypes, Inqlab-91, Chakwal-97, Rawal-87 and Kohsar-95, tested against five irrigation levels with drought imposed at different growth stages including control, terminal drought, post-anthesis drought, three irrigations and pre-anthesis drought. The parameters studied were flag leaf area, ear stalk length, number of grains per spike and grain yield per pot. Flag leaf area and ear stalk length exhibited a significant reduction of 14 and 36%, respectively, when wheat was subjected to water stress. The proportional reduction in yield was 40% with three irrigations and 98% in the case of pre-anthesis drought depending upon the extent and degree of stress. Results showed that wheat could withstand and tolerate drought only up to anthesis, after which water stress resulted in the complete failure of the crop. It could be deduced that the critical stage for moisture in wheat started 60 days after germination, and became more severe at 90 days, i.e. at the anthesis stage. Among the genotypes, Inqlab-91 was found to be more tolerant of drought and could thus be a good option for further testing and recommendation for rainfed areas.
A diallel cross involving six wheat varieties, namely Sehar 06, Punjab 96, GA 2002, Barani 83, Kohistan 97 and Chakwal 86 was carried out to determine the mode of gene action for some physio-morphological traits under water stress conditions. Analysis of variance showed highly significant differences among genotypes for all the traits studied. Additive type of gene action with partial dominance was observed for flag leaf area, stomatal frequency, leaf venation, days to heading and spike density while 100-grain weight was controlled by over dominance. Additive type of gene actions shows the fruitfulness of early selection for the traits while over dominance type of gene action indicates selection in later generations. Epistasis was absent for all the traits studied.
Authors:H. Sharma, R. Behl, K. Singh, N. Narula, and P. Jain
Field experiments were conducted over two years under low input conditions to know the influence of bio-inoculants, namely arbuscular mycorrhiza fungi (AMF,
Azotobacter chroococcum (Azc)
on the performance and gene effects for important root and plant characters in three crosses of wheat (WH147×WH157, WH147×PBW175 and WH147×WH542). Six generations representing P
populations of each cross were grown in randomized block design with three replications. The estimate of means (m) indicated that bio-inoculants enhanced the mean performance of most of the characters and root length density and grain yield in some crosses only. Crop season also showed considerable effect on impact of bio-inoculants. The joint scaling test revealed adequacy of additive-dominance model of gene effects for root biomass, root length density, flag leaf area, tillers/plant, grain weight and grain yield in all the crosses and bio-inoculants treatments in both years. The AMF treatment brought about changes in the magnitude and significance of additive component for root biomass, plant height, flag leaf area in all the three crosses. Both additive (d) and dominance (h) components were affected with respect to grain yield in WH147×WH157 and WH147×WH542. The dominant component was important for tillers/plant, grain yield, root length in control, as well as bio-inoculants treated populations of WH147×PBW175 but treatment of AMF and AMF+
reduced the magnitude of h and increased the magnitude of d. Digenic interactions were prominent for grains/spike in WH147×WH157. Magnitude of digenic interactions was higher under bio-inoculation. Simple pedigree and bulk pedigree methods are suggested to capitalize on adequate additive gene effects for developing bio-inoculants responsive wheat genotypes.
Authors:M.Z. Islam, M.A. Siddique, N. Akter, M.F.R.K. Prince, M.R. Islam, M. Anisuzzaman, and M.A.K. Mian
Genetic diversity of 28 restorer lines of rice was studied under irrigated condition through Mahalanobis D2 statistics and simple sequence repeat (SSR) banding patterns. The cluster analysis grouped the lines into five clusters. The principal component analysis showed that the first four components with vector values > 1 contributed 76.32% of the total variations. The intra- and inter-cluster distances were the maximum in cluster V (0.86) and between clusters II and V (15.14), respectively. Flag leaf area, plant height, panicle length, five panicle weight, primary branches per panicle and secondary branches per panicle had maximum contribution towards genetic divergence. A total of 24 alleles varied from 2 to 5 with an average of 2.67 alleles per locus were detected for the nine microsatellite markers across 28 lines. The polymorphism information content (PIC) values ranged from 0.12 to 0.71 with an average of 0.29. RM229 was considered as the best markers on the basis of the highest PIC value. Phylogenetic cluster analysis of the SSR data based on distance divided all lines into three groups (A, B and C), whereas the cluster analysis divided these lines into five groups (I, II, III, IV and V). Besides, evaluation of yield contributing traits demonstrated that the restorer lines under the current study possessed a considerable genetic diversity. Potential lines such as BU1IR, China2R, China1R, BHD3R, IR509R and Heera5R can be used as pollen parent in developing new commercial hybrid varieties. Therefore, potential restorer lines need to be conserved in Genebank for future hybrid rice breeding programs.