COMBINING GENES FOR ENHANCING RUST RESISTANCE AND HIGH YIELD IN WHEAT WITH PHENOTYPIC AND MOLECULAR MARKERS

摘要

Epidemics of leaf, stripe and stem rust on wheat have induced significant losses in the past during the early nineteenth century and would continue to be a major threat to future wheat production. Constant threat of leaf and stripe rust in Pakistan and stem rust throughout the world would prevail due to evolution of new rust races and favorable environments. Chemical control of these ailments remained unaffordable for poor farmers; hence the only effective strategy to avert the losses is the development of rust resistant varieties. Therefore, the hypothesis was to explore high yield and rust resistance potential through combining lines with high yield + durable rust resistance genes among the existing germplasm. So the current study was designed to combine genes for enhancing rust resistance and high yield potential in wheat. The parents' lines were selected on the basis of slow rusting history, phenotypic characters for durable rust resistance genes by the selection of desirable parents used in filial generations (F1 to F5). Total 750 head rows were planted in F6 from selected heads among F5 generation. Among these 750 single head rows planted in Kaghan, 345 lines were selected on the basis of agronomic traits and rust resistance performance. These 345 lines were put in yield testing study to select the high yielding and rust resistance lines. Among 345 lines, two hundred and twenty lines were selected on the basis of high yield rust resistance which was evaluated for the presence of durable rust resistant genes through phenotypic and molecular markers. It was confirmed that the lines showing durable, rust resistance possess Lr34/Yr18, Lr46/Yr29 and Sr2/Yr30 genes in combination or individuals from these lines. They are associated with several traits like pseudo black chaff (Pbc), leaf tip necrosis (Ltn) and adult plant resistance (APR) contributing to near immunity to leaf, stripe and stem rust infection. So these studies confirm the presence of durable rust resistant genes in finally selected lines on the basis of yield and rust resistance supported by phenotypic and molecular markers. The most prominent crosses yielded lines with FRT/SA42//PRL/SA42/3/ Wblli 2*/Kiritati (V-11211), Wattan/2*ERA/2/Pak81/2*Wattan/3/Shafaq/4/Brambling (V11212,V-11218 and V-11227) Luan/Kohistan/ Pak81/3/Kiritati (V-11262), Wattan/ 2*ERA/ 2/Pak81/2*Wattan/3/Shafaq06/4/Kingbird (V-11288), SH88/90A204//MH97//PRL/2*Pastor (V-11296), Shafaq06/Luan//MH97 (V-11304, V-11308 and V-11319), Uqab-2000/Wattan ud/Lr28//Yecora (V-11338), Wattan/2*ERA//V-04178 (V-11353), Wattan/2*ERA//V03007 (V11365) and Lasani-2008/Iqbal-2000 (V-11396). These are the most brilliant lines which have derived from the above crosses and showed the combination of three designated slow rusting /durable genes. These lines were high yielding with better resistance than all existing approved wheat varieties of the country. None of these lines had complete resistance, but were of slow rusting type and were suitable for commercial cultivation. The resistance is most probably by the additive effect of partial resistance genes accumulated from the diversified parents crossed with each other. Monitoring of the rust virulence pattern was conducted to monitor the virulent pattern in the country through avirulence/virulence formula. The survey was carried out on the rust trap nurseries planted at different agroecological condition in Pakistan. The rust trap nursery consisted of 40 Lr differentials and 24 Yr differentials. The studies revealed that there were no virulence observed for Lr9, Lr19, Lr25, Lr28, Lr27+31, Lr32, Lr34, Lr36, Lr23+Gaza and Lr37, and Yr1, Yr3, Yr5, Yr8, Yr10, udYr15, Yr18,Yrcv and Yrsp during the study period. Among the varieties Iqbal-2000, Uqab2000, Lasani-2008, Faisalabad-2008, AARI-2011, Millat-2011 and Pb-2011 exhibited resistance both for LR and YR. Moderate YR was observed on Shafaq-2006 and Chenab-2000 ranging from 20-30 MRMS.