Aegilops ovata: a potential gene source for improvement of salt tolerance of wheat

Abstract

Salt tolerant accessions of Ae. ovata were selected for hybridizationwith different tetraploid wheat varieties (Triticum durum). The F1hybrids were top crossed with different hexaploid wheat cultivars. The42 chromosome advanced derivatives (mostly BC2F3) were tested onartificially saline fields located at NIAB and ranging in ECe between8-10 dS.m(-1). The experiment was conducted during 1995-96 in aRandomized Complete Block Design with three replications. The objectiveswere to transfer salt tolerant gene(s) from Ae. ovata to cultivatedwheat varieties and to diversify the genetic base of exiting salttolerant wheat germplasm to be grown on saline lands.For hybridization, simple emasculation (or clipping of florets forbackcrossing) and pollination technique was employed. Immature embryoswere rescued only where necessary. Cytological and morphologicallystable advanced derivative (BC2F3) were tested on saline blocks usingsaline irrigation of EC15dS.m(-1) made artificially. Data with respectto variation in crossability, back cross (top crossed) seed productionand cytological status was collected during the growth period. Plantswere harvested at maturity and data on total biomass grain yield andharvest index was collected. Results were statistically analyzed usingAnalysis of Variance and Duncan' Multiple Range Test.Significant variation in crossability of tetraploid wheats with salttolerant accessions of Ae. ovata that ranges between 10-30% seed setwere observed. Maximum seed set (30%) was obtained for crosses of wheatvariety Durum with Ae. ovata ace. 65 while minimum crossability valueswere obtained for crosses of Akrache-2 with Ae. ovata accession 276978.Within the wheat varieties, variation in crossability of a particularaccession of Ae. ovata was not significant while between different Ae.ovata accessions, variation in crossibility with any particular wheatvariety was significant. Topcross seed production also showedsignificant variation which ranged between 10% (H-19/Ae.ovata:369580//Pasban-90) as minimum and 40% as maximum in H-19/ Ae.ovata //Pasban-90.Production of biomass and grain yield under saline field wassignificantly different from biomass and grain yield obtained undernon-saline control. Harvest index of advanced derivatives on the otherhand improved. Within the saline and non saline (control) fields thedifference in biomass production (7570-9377 kg.h(-1)) between differentderivatives was generally non-significant however, difference for grainyield which ranges between 1088-2701 kg/h was highly significant. Whenthe grain yield and biomass of hexaploid wheat varieties growing underthe same saline and non-saline control was compared with the advancedderivatives, the differences were again highly significant. It wasinteresting to note that when the advanced derivatives were grown undersaline field, reduction as compared to control in biomass and grainyield was 39.40 and 21.50% respectively. However, when hexaploid wheatline were grown under saline fields, the reduction in biomass and grainyield as compared to control was 49.37 and 64.82% respectively anddifference between the two was highly significant. The results indicatedthe anticipated transfer salt tolerant gene(s) from Ae. ovata tohexaploid wheat. Possibility of using the germplasm for cultivation ofsaline lands would be discussed with special reference to significanceof Ae. ovata in wide hybridization.