Estimation of Heritability in F2 Generation of Bread Wheat (TriticumaestivumL.)

Objectives: To estimate the heritability in a broad sense and the genetic advance F2 generation of bread wheat. Methods/Statistical Analysis: The collected data were statistically analyzed for analysis of variance by Gomez and Gomez, heritability in a broad sense and the genetic advance was worked out after Falconer. Findings: The results showed that genotypes parents, percent x crosses were highly significant at 0.01 level for days to 75% heading, days to 90% maturity, plant height (cm), tiller plant1, spike length (cm), spikelet spike-1, grain spike-1, grain yield plant-1 (g), Biological yield and harvest index (%) while seed index (1000 grain weight, g) showed non-significant for parents vs crosses. Mean performance of six commercial and F2 hybrids revealed that early heading (62.2) presented by Kiran-95 and his F2 hybrids (59.95%), days to 75% heading taken by Benazir x TD-1, minimum days (114.8) to 90% maturity shown by variety TJ-83, dwarf plant (59.82cm) shown by variety Hamal. The maximum tiller plant-1 (13.76) produced by cross Benazir x TD-1, longer spike length (9.95cm) shown by the variety Kiran-95, while the genotype TD-1 produced maximum number of spikelet spike-1 (20.76), maximum grain spike-1 (56.03) highest grain yield plant-1 (30.53 g) and highest biological yield was obtained from the cross TD-1 x Sindhu. Highest weight for 1000-grain was recorded for TD-1, (50.20). The highest biological yield was shown by Benazir (61.03g). Among the hybrids, higher grain yield plant-1 displayed by Sindhu x Kiran-95, within the F2 population maximum harvest index of 56.45% was observed in Sindhu x TJ-83. The cross Benazir x TD -1 showed higher heritability for tiller plant-1, spike length, spikelets spike-1 and harvest index. While Benazir x Sindhu exhibited higher heritability for grain spike-1, plant height. Variety TD-1, Kiran-95, and Sindhu may be selected in further breeding programs and crossed Benazir x TD-1 could be evaluated in the subsequent generation and selection could be made on spikelets spike-1 and harvest index. Application/Improvements: The variety TD-1 performs better in spikelets spike-1, grains spike-1, grain yield plant-1, seed index, while variety Kiran-95 had higher in spike length, and harvest index. *Author for correspondence Indian Journal of Science and Technology, Vol 12(24), DOI: 10.17485/ijst/2019/v12i24/144871, June 2019 ISSN (Print) : 0974-6846 ISSN (Online) : 0974-5645


Introduction
Southwestern Asia is the region where the wheat crop has been cultivated in, which is its geographic center of origin, since more than 10,000 years. Its related wild species still grow in Lebanon, Eastern Turkey, Syria, Iraq, and Northern Israel. Human began breeding wheat in the early 1800s from then, the improvement in the yield and grain quality has been noticed, modifications in the plant architecture and increased resistance to drought, lodging, insect-pest and disease pathogens 1 .
Wheat is an important part of human nutrition in all parts of the world. For the world's population, it is an important cereal crop and staple food. Wheat is a globally significant crop that grows in diverse environments 2 . Wheat is consumed in various forms and is consumed by populations such as bread, crepes, porridge, flour, and suji. Among cereal crops, the wheat yield is a complex quantitative feature and an incentive for many yield contributors. These characteristics directly or indirectly affect grain production, and breeders are naturally interested in investigating the degree and type of association of these traits 3 . Wheat is an important food crop in the world and a source of food and livelihood for more than 1 billion people in developing countries. It is considered to be one of the "three major cereal crops". Rice, wheat, and corn. Today, more than 200 million hectares of wheat cultivated in the world is the most important agricultural product in international trade 4 . Approximately 35% of the world's population feeds on this 5 . Wheat (Triticumaestivum L.) is the main grain grown not only in Pakistan but throughout the world. Pakistan is one of the top ten wheat producers, with 80% of the agricultural community growing wheat. Wheat production in 2015-16 increased from 8.69 million hectares to 25.4 million tons, showing an increase of 3.2% in the region with an average yield of 2,787 kg per hectare. In 2015-16, wheat accounted for 9.9% of agricultural value added and 2.0% of Pakistan's GDP. The area planted with wheat increased from 9.204 million hectares last year to 9.26 million hectares, an increase of 0.6%. Wheat production in 2015-16 was 25.482 million tons, an increase of 1.6% from last year's output of 250.86 million tons 6 . As crops are sown at the right time and available moisture, especially at the Barani Track, the use of germination/ growth and availability and inputs is still sufficient, and production is increasing. Depending on the climate, seed type, and soil conditions, it usually takes between 150 and 180 days between planting and harvesting. It is the world's most widely grown crop, accounting for about one-sixth of the total area of cultivated land. Wheat has been extensively and continuously researched to maximize food production while also increasing food production per unit area. However, there is still considerable room for improvement, especially in order to expand the ongoing genetic improvement efforts of wheat to meet the growing needs of a growing population. Genetic manipulation is the best way to increase wheat yield. It is necessary to estimate and study the genetic variation and genetic patterns of different plant parameters in order to initiate an effective wheat breeding program. The stagnant wheat production in Pakistan is due to the limited diversity of germplasm in breeding programs 7 .
In order to develop effective breeding strategies for crops, important knowledge of the genetic traits of quantitative traits is also essential. In this case, the heritability of the trait/genotype contributes to plant breeding to predict the behavior of subsequent generations to make the desired selection 8 . Heritability studies provide breeders with valuable genetic information to predict the interaction of genes in isolated generations. Observations of hereditary and genetic progression have led us to understand the inheritance of parents and their responses to their offspring. Heritability is an estimate of the genetic part of the physical appearance. Heritability and genetic progression values help us make choices more effective and estimate responses to choices 9,10 . Heritability is a component of the phenotype determined by genetic factors 11 . If the environmental variability associated with genetic differences is small, the choice will be more effective 12 . Studies of statistical parameters such as mean, variance, heritability, and genetic progression help us measure the genetic diversity, genetic potential, and stability of any genotype 13, 14 .

Material And Methods
The experiment was carried out at Southern wheat research station Tando Jam, during rabi season 2016-2017. The experiment was conducted in a randomized complete block design (RCBD) with three replications using 6 varieties and their 15 F 2 hybrids. The sowing was done by dibbling with the space of 22.5 cm between row to row and 7.5cm between in plants. Vol  Statistical Analysis : The collected data were statistically analyzed for analysis of variance by Gomez and Gomez 15 (1984), heritability in a broad sense and the genetic advance was worked out after Falconer 16 (1987).

Analysis of Variance
The mean square regarding genotype, parent, and crosses were highly significant (P > 0.01) for all the traits studied, while parents vs crosses (p × c) were highly significant at P > 0.01 level of probability for all the traits studied except seed index which is non-significant (Table 1).

Mean Performance
Days to 75% Heading: Mean performance of six commercial varieties among parental lines and their F 2 hybrids presented in Table 2   Tillers Plant -1 : Productive tiller plant -1 have a straight impact on grain yield plant -1 . The variety Kiran-95 produced a minimum number of tillers plant -1 (5.16) and a maximum number of tillers plant -1 (7.76) produced by variety TJ-83 (Tabel 2). In the case of hybrids, a minimum number of tillers plant -1 (7.70) produced by cross HAMAL x TJ-83 and a maximum number of tillers plant -1 (13.6) was produced by cross Benazir x TD-1.
Spike Length (cm): Table 2 revealed that longer spike length (9.95 cm) obtained by the variety Kiran-95 whereas the lower spike length (7.35cm) measured by variety Hamal. In the case of hybrids, maximum spike length (14.74 cm) was measured by cross Benazir x TD-1 and minimum spike length (7.71 cm) was measured by cross TD-1 x TJ-83.
Spikelets Spike -1 : According to results presented in Table 2 depicted that the genotype TD-1 had a maximum number of spikelets spike -1 (20.76), while minimum spikelets spike -1 was counted by variety Hamal (13.26). In the case of hybrids, a maximum number of spikelets spike -1 (22.80) counted by cross Benazir x Sindhu and minimum number for spikelets spike -1 (17.66) was obtained by cross Hamal x TD-1 ( Table 2).
Grain Yield Plant -1 : The data revealed that the highest grain yield plant -1 was (30.53) for the parental genotype TD-1 and lowest grain yield plant -1 was recorded in Hamal (21.19 g). In the case of hybrids, maximum grain yield plant -1 (31.43) was obtained by cross TD-1 x Sindhu and minimum grain yield plant -1 (18.94) was shown by cross Hamal x TD-1.
Biological Yield Plant -1 : The data disclosed that the highest biological yield plant -1 (61.03 g) was measured by parental genotype Benazir whereas the lowest biological yield plant -1 was observed in Hamal (41.74). In the case of hybrids maximum biological weight (63.03 g) was noticed in cross TD-1 x Sindhu and minimum biological yield plant -1 (37.52g) measured by cross Hamal x TD-1.
Seed Index (1000-grain weight) (g): It is one the important character that determines the actual grain yield. Highest weight for 1000-grain was recorded for TD-1 (50.2 g) and the lowest weight for 1000-grain was observed in variety Hamal (41.53 g), Among the cross combinations TD-1 X TJ-83 had greater (51.41g) weight for 1000-grains and the lowest seed index was noticed for Hamal x TJ-83 (41.0 g).
Harvest Index (%): Most of the wheat cultivar revealed good harvest index extending between 47.94% to 59.95%. Although, the highest harvest index of 59.95% was manifested in wheat variety Kiran-95. The lowest harvest index of 47.94% was displayed by the variety Benazir. Within the F 2 populations, maximum harvest index of 56.45% was revealed by Benazir x Kiran-95, while the lowest harvest index of 43.53% was displayed by in TD-1 x Kiran-95.

Heritability
Days to 75 % Heading: Genetic analysis of days to 75% heading displayed ( Table 3) that all the crosses showed high heritability the range of genotypic and phenotypic Spike Length: Table 7 showed the heritability for the character spike length which displayed that all the crosses displayed high heritability, the range of genotypic and phenotypic variance ranged from 11.27 and 15.77    (Table 9).
Grain Yield Plant -1 : Grain yield plant -1 displayed that all the crosses showed high heritability, the range of genotypic and phenotypic variance ranged from 78.88 and 94.46 by Hamal x TD-1 to 230.24 and 244.97 by TD-1 x Sindhu respectively. The highest heritability (94.09%) obtained by Sindhu x Kiran -95 followed by TD-1 X Sindhu. The lowest heritability and genetic advance noticed by cross Hamal x TD-1 (Table 10).
Biological Yield Plant -1 : Higher heritability was shown by all the crosses studied for the character biological yield plant -1 the range of genotypic and phenotypic variance    (Table 12).
Harvest Index: Heritability for the character harvest index presented in Table 13 revealed that all the crosses showed higher heritability. The range of genotypic and    24 . Reported the magnitude of the phenotypic coefficient of variance recorded for grain yield pant -1 , whereas high heritability for days heading to 50% was being reported. While 25 reported higher heritability for days to 50% flowering. The higher heritability of 50% flowering in connected with higher genotypic variance, modern wheat is dwarf in height therefore the vegetative period of dwarf variety is shorter as compared to the old wheat. Plant height displayed that all the crossed should high heritability the range of genotypic and phenotypic variance ranges from 1416. 33  Worked out low heritability for kernel weight per spike and explained that traits can be enhanced easily due to the high value of heritability and phenotypic variance. While 34, 35 worked out high heritability along with high genetic advance for 1000 grain weight that was due to the additive genetic effects 36 . Worked out heritability of seed index in two F 2 populations and conducted that cross combination and their parental lines must be given due consideration in a subsequent generation or further breeding programs.

Conclusions
• The mean square regarding genotype, parent, and crosses were highly significant (P > 0.01) for all the traits studied, while parents vs crosses (p × c) were highly significant at P > 0.01 level of probability for all the traits studied except seed index which is non-significant.
• The variety TD-1 performs better in spikelets spike -1 , grains spike -1 , grain yield plant -1 , seed index, while variety Kiran-95 had higher in spike length, and harvest index.
• The cross Benazir x TD-1 showed higher heritability for tillers plant -1 , spike length, spikelets spike -1 , and harvest index. While Benazir x Sindhu exhibited higher heritability for grains spike -1 and plant height.