Breeding rust resistant cultivars using conventional methods is time-consuming, complex and slow, but molecular markers offer a rapid alternative for developing cultivars with improved disease resistance. Three wheat cultivars, DBW88, DBW107, and DBW110, from different production zones were used as recipients for incorporation of resistance genes using a marker-assisted backcross (MAB) breeding approach. Leaf rust resistance gene Lr32 is being incorporated into all the three varieties, stripe rust resistance gene Yr15 is being incorporated into DBW88 and DBW107, and stem rust resistance gene Sr26 is being added to variety DBW110. Lines PBW703 (Yr15), FLW15 (Lr32) and Avocet (Sr26) were used as donors. Six cross combinations viz., DBW88/PBW703, DBW107/PBW703, DBW88/FLW15, DBW107/FLW15, DBW110/FLW15 and DBW110/Sr26 were made at Karnal during 2015-16 and the crosses were grown at IIWBR-RS, Dalang Maidan for backcrossing. BC1F1 plants were raised at Karnal during 2016-17. Both foreground and background selections were practiced in each combination. SSR markers gwm264 and barc135 were used for foreground selection of Lr32, marker barc8 was used for selection of Yr15, and markers Sr26#43 and BE518379 were used to detect presence and absence of Sr26. From 90 to 127 polymorphic SSR markers chosen for each cross from an initial set of 800 screened on the parents are being used for background selection.
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Rust diseases are among the most important affecting wheat because they are responsible for a significant yield reduction globally. Different types of conventional breeding approaches are currently underway to protect wheat from these diseases. The involvement of molecular genetics and biotechnology tools in conventional plant breeding sets new directions to develop crop varieties with desired traits more efficiently and accurately. An array of molecular markers linked to rust resistant genes and dense molecular genetic maps are now available for use. Marker assisted selection (MAS) is now a routine activity in various crops especially for agronomic traits that are otherwise difficult to tag like resistance to pathogens, insects, nematodes etc. Gene pyramiding involves the stacking of many genes leading to real-time expression of all genes in single variety to develop durable resistance. This method is gaining significant popularity as it would enhance the efficiency of conventional breeding methods and precise development of broad spectrum resistant capabilities. Keeping in view the significance of MAS, rust resistant wheat parental lines were selected and molecular information was tagged using gene linked markers through PCR. Conventional breeding plane was designed on the basis of molecular data and maximum crosses were made between high yielding susceptible and resistant wheat genotypes. Molecular screening and other yield parameters were keenly noted on each stage of segregating population. Three rust resistant genes i.e. Lr-34/Yr-18, Lr-46/Yr-29 and Lr-19 were successfully combined in three cross combinations. Twenty crosses were found positive for two resistant genes i.e. Lr-46/Yr-29 and Lr-19, Moreover, one cross was positive for Lr-34/Yr-18 and Lr-46/Yr-29, and one was positive for Lr-34/Yr-18 and Lr-19. Introduction of more genes is also continued to develop superior resistance against a wide range of rust pathogen in wheat.
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.
Rusts continue to cause significant losses in grain yield of wheat in Iraq. Substitution of susceptible cultivars with resistant ones is an important step in reducing the vulnerability of the wheat crop. The present study represents a breeding program to develop high yielding bread wheat cultivars with resistance to brown rust and yellow rust. The performance of 265 spring wheat genotypes representing an international bread wheat-screening nursery from CIMMYT were evaluated in different agro-ecological zones in comparison with local commercial cultivars. Adult plant stage screening of the materials for brown rust and yellow rust reaction under inoculated conditions for three successive seasons identified 29 resistant and 59 moderately resistant genotypes, and 79 genotypes out-yielded the local cultivars. The selected lines were comprehensively evaluated for grain yield potential and disease response in different locations and agro-systems. Among 13 genotypes line 172 was selected for higher grain yield than local commercial cultivars in the presence and absence of both diseases. Mean coefficients of infection on line 172 were 0.57 and 5.35 to brown rust and yellow rust, respectively. It was also moderately resistant to common bunt. Yield potential of the new cv. Alaa was 9-20% higher than the commercial local cultivars Araz, Tamuz 2 and Adana. Alaa was registered and released by the National Committee for Registration and Release of Agricultural Cultivars according to order no. 39, 30/10/2017 as a new cultivar with high yield potential and resistance to brown rust and yellow rust. Great emphasis was made on multiplication and delivery of seeds to farmers. Grain yield potential of Alaa on a farm scale is 3,372 Kg/ha under rain-fed conditions and 5,024 Kg/ha under irrigated conditions.
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.