In the present study five bread wheat genotypes (9797, 9801, 9802, Chakwal-50 and Chakwal-86) were tested in a 5?5 full diallel analysis for the estimation of combining ability for yield and its related traits. In randomized complete block design (RCBD) twenty F1s along with their parents were planted in field with three replications in the research area of Department of Plant Breeding and Genetics, University of Agriculture, during 2014-15. Plant height, No. of grains/spike, spike length, No. of productive tillers/plant, flag leaf area, No. of spikelets/spike, 1000 grain weight and grain yield per plant were studied. Except spike length mean squares due to GCA were highly significant for all the traits. All the characters showed highly significant mean squares for SCA and RCA. SCA variance was lower than GCA variance for number of grains/spike and spike length presenting the major role of additive gene action in the inheritance of these traits. While for plant height, flag leaf area, number of spikelets/spike, number of fertile tillers/plant, 1000 grain weight and grain yield/plant the value of GCA variance was lower than the value of SCA variance exhibiting non-additive gene action. Chakwal-50 was the best general combiner for plant height, spike length, number of spikelets/spike, number of grains/spike and grain yield/plant. The best specific combination for most of the traits was 9802?Chakwal-86. In future wheat breeding research programmes, good specific and general combiners can be exploited.
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Global warming affects the environmental parameters of agro-based countries like temperature increase, melting of glaciers, floods, erratic rains, low temperature, frost and high temperature. As a result agriculture is becoming more vulnerable to global environmental shifts. In case of wheat, erratic or low rains badly affect the wheat crop of rainfed areas of the country along with high temperature at seedling or juvenile stage. Similarly, frost affects the early sown wheat crop in irrigated areas of Punjab. Lesser availability of irrigation water from water reservoirs also reduces the wheat crop productivity. Sudden increase in temperature (>30?C) during the month of March adversely affect the grain filling. High temperature during grain filling stage interferes with the photosynthetic activities of the plant due to enhanced maturity, grain become shriveled and results in low grain yield. The threat of these environmental changes can only be overcome through breeding with specific objectives which is cost effective once obtained.
Hence development of wheat varieties for frost, drought and heat tolerance is the only feasible solution to combat these stresses which is being used at Wheat Program of Ayub Agricultural Research Institute, Faisalabad, Pakistan. New emphasis is also being given to develop frost resistant wheat varieties due to changing scenario of last few years. The institute is actively involved for the development of heat, drought and frost tolerant wheat varieties. During working for tolerance against any of these stresses plant types to be breed are physiologically and morphologically modeled in such a way that they should be capable of tolerating respective stress. In addition to breeding work an extensive research is also being done at Wheat Research Institute, AARI., Faisalabad to investigate best agronomic strategies to make wheat crop best adapted to environmental stress conditions.
Wheat is an important cereal crop and staple food in Pakistan. Most of the wheat is cultivated late after cotton, rice and sugarcane. Introduction of long duration Bt cotton varieties further pushed its sowing to late December or even early January. Late sowing of wheat crop results in yield loss in the Punjab province. A study has been conducted in experimental fields of Wheat Research Institute, AARI, Faisalabad, Pakistan to find out the possible reasons of low grain yields in late sown crop. Twelve experimental wheat lines were planted on seven sowing dates starting from 1st November to 30th December with ten days interval. The experimental design was a factorial combination of seven sowing dates as main plots and twelve varieties/ genotypes as subplots in a split-plot design with three replications. Effect of temperature on several crop growth stages was studied. Mean minimum temperature during the month of December, 2016 and January, 2017 remained below 5?C and mean maximum was more than 30?C during March 2017. Weather conditions experienced by the crop at each developmental stage were compared with the optimum conditions required on that specific stage in each sowing date. It was revealed that in late sown crop, different phonological/growth stages of the crop and yield components and grain yield were affected negatively. It was concluded from the study that the late sown crop suffered from two types of temperature stresses. The late sown crop faced low temperature stress at starting phase which result in delayed germination and low tillering. At caryopsis formation and grain filling the same crop face high temperature stress causing reduced grain formation and shriveled grains due to enforced maturity. Sowing of wheat at proper time i.e., by the end of November was recommended to fetch maximum yields.
Under changing climatic conditions, the emergence of new diseases or new races of existing diseases is a serious threat to global wheat production. Particularly, the presence of wheat blast in Bangladesh and stem rust race Ug99 in Iran, created a fearsome and intractable situation for Pakistan. A study was planned for monitoring and surveillance of the wheat blast and rust pathogens in wheat growing districts of Punjab, Pakistan during the cropping season 2016-17 as vigilance program. During the survey, one hundred and seventy one wheat fields of upper and central Punjab region were monitored and two types of Rusts (Leaf Rust & Yellow Rust) were recorded in varying intensity on different varieties of wheat. Out of 171 locations 86 spots were free from both types of rusts i.e. Leaf Rust & Yellow Rust, while the remaining locations were found to be infected with both leaf and yellow rust. However, all the surveyed fields were free from the stem rust infestation. Among the infected fields, 23 were infected by Leaf Rust while 63 fields were infected by Yellow Rust.The susceptible type of rust attack was noticed on old/ banned/ unapproved wheat varieties. Moderately resistant to resistant reaction was observed on newly approved varieties. The rust infected samples having S or MS type infection were collected for race analysis. Similarly, blast suspected samples were analyzed in laboratory and none of the tested samples showed the presence of wheat blast pathogen, which indicates no need to panic but vigilant in future.
Resistance breeding for wheat leaf rust requires testing of breeding materials under field conditions, which must be complemented with diagnostic molecular makers. A set of 28 exotic wheat lines from advanced CIMMYT material along with three check varieties (Siran, Atta-Habib, Ghanimat-e-IBGE) were tested at three contrasting locations (Peshawar, Mansehra and Lakki-Marwat) and were genotyped with markers linked to three Lr genes (LrPr, Lr37, and Lr34). The overall leaf rust pressure was low during the wheat season of 2015-16, with the maximum disease observed at Lakki-Marwat (up to 70%), followed by Peshawar (up to 50%) and the minimum disease at Mansehra (up to 30%). Despite the overall low leaf rust pressure, the germplasm behaved variably in terms of leaf rust resistance as revealed through average co-efficient of infection (ACI). According to ACI value, 16 out of 28 genotypes were completely resistant, while few genotypes showed partial resistance. The maximum CI value was recorded for wheat line W-SA-87, which was 55 at Lakki Marwat, 33 at Peshawar and 15 at Mansehra, while 18 lines had CI value of zero across the three locations. Variability existed in yield parameters with W-SA-84, W-SA-78 and W-SA-79 producing the better grain yield. Genotyping with Lr linked markers viz., STS-7 (LrPr), SC-Y15 (linked with Lr37) and csLV34 (linked with Lr34) revealed that among the tested lines LrPr was the most frequent (83.8%), present in 26 lines; followed by Lr37 (77.4%), present in 24 lines, while Lr34 was present in 16 lines (71.1%). All three genes were detected in 45% of the germplasm. Cluster analysis grouped the germplasm in four clusters based on both phenotypic and molecular markers data. The information generated in the present study would be valuable in resistance breeding for a better control of leaf rust disease in Pakistan.
To reduce losses caused by rusts, regular and timely replacement of susceptible varieties with new high yielding, rust resistant varieties must occur. Data from a farmer survey carried out across Pakistan (Punjab, Sindh, KPK and Baluchistan) in 2014 enabled an analysis of the uptake of rust resistant variety NARC 2011. The empirical results indicated that the major sources of information that farmers obtained about NARC 2011 were research stations (83%), seed companies (7%) and fellow farmers (5%). Although production inputs were applied equally to both rust resistant NARC 2011 and rust susceptible wheat varieties the average yield of NARC 2011 (5,063 kg/ha) was superior to high yielding but rust susceptible varieties (4,446 kg/ha). Quality attributes of NARC 2011, including taste, color, dough kneading and chapatti making properties, were preferred by >70% of farmers). Seed availability and accessibility of NARC 2011 were major issues. Farmer awareness of rusts, especially the threat of exotic Pgt race Ug99, needs to be improved.
Wheat rust is a group of deadly, constantly changing fungal pathogens that pose a serious threat worldwide and also equally most important in Pakistan. Three participatory wheat seed value chain workshops conducted in Pakistan in 2014 indicated the predominance of informal seed systems in Khyber Pakhtunkhwa and Pothwar region of Punjab. A relatively old and rust susceptible variety Sahar06 was covering nearly 50% area of irrigated wheat in Punjab while the coverage of TD-1 was nearly 75 % of wheat area in Sindh. Predominance of mega susceptible varieties with informal seed systems can be an important recipe for the outbreak of rust diseases threatening the stability of wheat production systems in Pakistan. It is challenging to continue to improve and sustain wheat productivity by reducing vulnerability of wheat varieties to rust diseases, both in time and space when more than 70% of wheat seed used comes from farmers' own farm saved seeds mostly of old and obsolete varieties. To address this, 17 recently released rust resistant wheat varieties with diversity in genetic background, adaptation and good yield potential have been deployed through a network of partners to nearly 10,000 smallholder farmers in parts of 62 districts of Pakistan. Varietal deployment was done by coordinating on farm participatory varietal selection with agronomic interventions and village level seed multiplication and marketing. Though, rusts pathogens can evolve into new strains that are more virulent and damaging to wheat crops, nevertheless, some of these varieties do carry known genes conferring resistance to yellow, leaf or stem rusts thereby help avert any sudden rust epidemics. This effort will be instrumental in improving the access to new seed varieties in the grassroots level and widening the genetic bases of wheat that will help in buffering the rust incidence and contribute to household food security of smallholder farmers in Pakistan.
With ongoing threats of rust from both internal and international sources it has become a priority at CIMMYT and for Pakistan national programs to accelerate the rate of seed increase and to popularize new Pgt race Ug99 resistant varieties to avert future disasters. Seed of Ug99 resistant varieties NARC-11, Pak-2013, Dharabi-2011 and BARS-09 was produced under the Wheat Productivity Enhancement Program (WPEP). The country-wide participatory approach involves a partnership of farmers, seed companies and research institutes. In 2014 16,020 and 6,085 kg of seed of NARC-11 and Pak-13, respectively, were distributed all over the country, including Azad Jammu Kashmir and Gilgit-Baltistan. Comparative yields across Pakistan show that the rust resistant varieties are equal, or superior, to current stem rust susceptible varieties grown by farmers. Deployment and use of these varieties by farmers in Balochistan will have a significant impact not only on productivity, but may also avert the consequences of possible introduction of race Ug99.
A set of 63 wheat landraces obtained from Institute of Agri-Biotechnology and Genetic Resources, NARC-Islamabad was screened for adult plant resistance (APR) at two inoculated locations during the 2012-13 cropping season, i.e. Wheat Research Institute (WRI), Faisalabad, for leaf rust and Cereal Crops Research Institute (CCRI), Pirsabak, for stripe rust. Responses based on coefficients of infection (CI) were recorded. Five landraces were susceptible (CI >60) and 39 were resistant to both rusts at the adult plant stage; 47 lines were resistant to leaf rust and 51 were resistant to stripe rust, with CI values of 0-20. Four landraces had moderate levels of APR (CI 21-40) to both rusts, 12 to leaf rust and 8 to stripe rust. Only two landraces (accessions 10975 and 11029) showed MR/MS reactions, and one (11438) had an MS/S reaction; the remaining produced S reactions to leaf rust at WRI. At CCRI Pirsabak, the majority of lines responded with MR/MRMS reactions, the remaining lines were susceptible. The 39 landraces identified to have resistance to both diseases may carry new APR gene(s) to one or both rusts, but must be further characterized prior to use as parents in national wheat breeding programs.
Resistance has been an environmentally friendly and proven means of controlling stem rust for more than a century; the problem is that resistance has not been durable. A collection of 100 wheat landrace accessions from the Institute of Agri-Biotechnology and Genetic Resources, NARC-Islamabad, was tested at the seedling stage for response to 11 of Pgt races with multiple virulences, including TTKSK (from Kenya), TRTTF (Yemen), TTTTF (USA), and RRTTF (Pakistan). Six accessions were resistant (IT 0; to 2) to race TTKSK, 11 to race RRTTF, and 9 to races TRTTF and TTTTF. Further tests with US races QTHJC and TPMKC indicated that the majority of these landraces were susceptible. The resistant landraces could be used as donor parents in crossing programs to broaden the genetic base for stem rust resistance in Pakistani wheat varieties.