Genetic potential and variability for phenological and yield attributes in facultative winter wheat

To feed ever growing world population, development of high yielding and disease resistant wheat varieties are of utmost importance. A set of 20 genotypes including 18 facultative winter wheat lines and two checks (Pirsabak-2005 & Pirsabak-2013) cultivar were evaluated at Cereal Crops Research Institute (CCRI), Pirsabak Nowshera Khyber Pakhtunkhwa-Pakistan during 2014-15 cropping season. Highly significant differences (P ≤ 0.01) were found among the facultative lines for all traits except biological yield. Days to heading, maturity, plant height, biological yield, grain yield and harvest index varied from 116 to 133 days, 152 to 168 days and 87 to 128 cm, 11805.56 to 16666.67 kg ha, 1627.78 to 4713.89 kg ha and 15.11 to 36.00% respectively. Based on mean performance, FWWL-6 was found best for days to heading and maturity as it headed and matured earlier than other lines. For reduced height, FWWL-7 was found best. Comparison of mean for grain yield showed that FWWL-14 produced the highest grain yield (4713.89 kg ha) as compared to other genotypes. Heritability estimates in broad sense for days to heading, maturity, plant height, grain yield, biological yield and harvest index was 0.81, 0.59, 0.86, 0.26, 0.70 and 0.83 respectively. Genetic advance (%) for days to heading, days to maturity, plant height, biological yield, grain yield and harvest index was 3.69, 2.61, 10.98, 4.83, 19.67 and 22.93 respectively. High heritability estimates for all the traits except biological yield, suggested that selection would be more effective to develop superior lines that could be used in future wheat improvement programs.


Introduction
Wheat (Triticum aestivium L.) is one of the most important cereal crops because of its high nutritive value, unique characteristics and its uses in a variety of products.Worldwide wheat is grown in many ecological zones.In Pakistan wheat was grown over an area of 8.69 million hectares which produced 24.2 million tons with an average yield of 2787 kg ha -1 while total area under wheat in Khyber Pakhtunkhwa was 0.72 million hectares [1].The average yield of Khyber Pakhtunkhwa province (1807 kg ha -1 ) is much lower than the national average yield (2787 kg ha -1 ).Among other factors, one of the major issues for low wheat productivity in the province are unavailability of high yielding, disease resistant cultivars suited best to semiarid and arid environment.Due to increase in population and current scenario of climatic change, demands of wheat are increasing consistently worldwide and in Pakistan.Therefore introducing new cultivars/ advanced lines with superior features like high yield, disease resistance and adaptation to arid and semiarid climates are the prerequisites (Brant., 2009) [2].Development of new high yielding cultivars requires a thorough knowledge of the existing genetic variation for economically important traits, features of genotypes (G), environment (E) and G × E interaction.Ideal genotype having high grain yield or component traits needs to express genetic potential revealing the lowest value of variance (σ 2 ) in diverse environmental growing factors.Yield is indeed a complex quantitative trait and selection on the basis of grain yield alone is in-effective as other component traits are not properly considered [3].Therefore, identification of those characters which reveals significant contribution to final grain yield is indispensable for efficient wheat breeding.Likewise, characters which are easily measurable and showing healthy heritability values & reflecting positive relationship with final yield have supreme importance to exercise indirect selection method for better yield [4].If the heritability for a character is higher than the selection will become much easier and thus response to selection will be greater [5].Wheat production must be increased by 40% till 2020 to meet the worldwide wheat demand."Increasing the intensity of production in those ecosystems that lend themselves to sustainable intensification, while decreasing intensity of production in the more fragile ecosystems" could be the possible solution for agriculture to be maintained with growing population [6].In addition, crop production enhancement really emphasized on grain yield potential (GYP), user preferences and stability of yield on a wide range of environments.In the current study 18 wheat lines which were selected from 21-Facultative winter wheat observation nursery for semi-arid (FAWWON-SA) nursery along with two checks were grown at CCRI, Pirsabak with the key objectives to determine potential of promising selected Facultative winter wheat lines for phonological and yield attributes. Estimate the genotypic variation and heritability for the studied traits.Testing of promising selected lines in advanced trials and its utilization in future wheat breeding.

Experimental material
Facultative CIMMYT nursery (21-FAWWONSA) was grown at CCRI, Pirsabak, during Rabi season 2013-14.Each line/ entry was composed of 2 rows having row length of 2 meter, with R-R spacing 30 cm.Among the 108 lines only 18 promising lines were chosen on the basis of better performance for final grain yield and physiological maturity and were promoted for further testing to advanced yield trial.

Experimental site
The present research was carried out at experimental field of Wheat Breeding Section at CCRI, Pirsabak, Nowshera, with coordinates of 34 0 N latitude, 72 0 E longitude and 288m height of sea level Khyber Pakhtunkhwa-Pakistan during Rabi season of 2014-15.The physico-chemical properties of experimental site was 0.82% organic matter, 4.2 ppm available phosphorous, 70 ppm available potassium with 0.13 dSm -1 EC and 8.1 pH.Selected 18 facultative winter wheat lines (FWWL) along with the two check cultivars i.e.Pirsabak-2013 and Pirsabak-2005 were evaluated in randomized complete block design with two replications.The detail of the lines used the study is presented in Table 1.Each line was properly sown in six rows with 5 meter length; row space was kept as 30 cm while plot size was 9 m 2 .Standard agronomic practices were followed throughout the cropping season.Data were recorded on days to heading, physiological maturity, plant height, biological yield, grain yield and harvest index.

Statistical analysis
The recorded data was statistically analyzed using analysis of variance technique by using statistix 8.1 software.Differences among wheat genotypes for different traits were examined by using least significant differences (LSD) with P at 0.05 and 0.01 probability levels.

Heritability
Broad sense heritability was calculated using the following formula.

Days to heading
In wheat earlier spike initiation is desired and wheat scientists are more concerned to develop new highly adapted wheat genotypes with earlier heading.Analysis of the data revealed significant differences (P ≤ 0.01) among the wheat genotypes for heading (Table 2).Highly significant genetic differences have also been reported by Abinasa et al. [8] in evaluating 24 sets of wheat genotypes for morphological traits including heading, maturity and grain yield.Similarly, Tesfaye et al. [9] also reported highly significant genetic differences in advanced bread-wheat lines for days to heading and harvest plus under well water conditions.Days to heading was ranging from 116 to 133 days, having average value (122 days).Wheat genotype FWW-6 was desired with its least days of 116 to heading (Table 3).Genotypic, phenotypic as well as error variance were 12.73, 15.72 and 2.99 respectively.Broad sense heritability for days to heading was high (0.81).High value for days to heading trait was also previously reported by Tazeen et al. [10].Hence higher values of heritability reflect the reliability and availing the supreme chance of the genotypes to be identified by its physical appearances [11].Genetic advance was low (3.69%) for heading (Table 4).Low genetic advance was also reported by [8] in spring wheat experiment evaluated for augmenting the agronomic traits including heading.In addition, medium to low heritability for important traits including heading was observed by Gupta and Verma [12] and suggested that selection should be effective either with high heritability in wheat.Biological yield (kg ha -1 ) Biological yield is vital factor and scientists emphasized on wheat genotypes with higher biological yield.Among lines, nonsignificant genetic differences (P ≤ 0.01) were observed for biological yield (Table 2).Similar differences among the genotypes for biological yield were also reported by Akçura.M [16].
Among the wheat genotypes the biological yield ranging from 11805.56 to 16666.67 kg per hectares with average value 14361.11kg per hectares.Wheat genotypes FWWL-1 as well as FWWL-12 were attractive for having maximum biological yield as compared to other wheat genotypes evaluated (Table 3).Genotypic, phenotypic as well as error variance were 941493.39,3609215.94 and 2667722.55,respectively.Low heritability (broad sense) of 0.26 was recorded for biological yield.Genetic advance for biological yield was low (4.83%) (Table 4).Our results are supported by the findings of Sachan and Singh [17] and Akçura M [16] reported low heritability as well as low genetic advance for yield traits.However, our results are in contrast with the earlier findings of Abinasa et al., [8] whose reported moderate to high heritability for biological yield in evaluating 36 set of spring wheat advanced lines.Grain yield (kg ha -1 ) Increase in grain yield is the decisive target of most wheat programs and availability of diversity in breeding material is hence essential for the improvement of grain yield in wheat.Hence, wheat genotypes with more grain yield are very imperative for plant breeders to focus on maximizing wheat production.Highly significant differences (P heritability broad based, Vg= Genetic variance Vp= Phenotypic variance = Vg +Ve Where, MSG= Mean squares due to genotypes MSE= Mean squares due to error Ve= Error variance r= replication Genetic advance (GA) Genetic advance (GA) was calculated by mentioned formula described by [7].Genetic Advance = i ph 2 Similarly, I is the selection intensity and its value is 1.75 at 10 p is the phenotypic std.deviation h 2 (B.S) = heritability Broad based.