Marker-Assisted Pyramiding of Downy Mildew-Resistant Gene Ppa3 and Black Rot-Resistant Gene Xca1bo in Popular Early Cauliflower Variety Pusa Meghna

Cauliflower is an important extensively grown cool season vegetable in India. Black rot and downy mildew are major devastating diseases reducing yield and quality of the crop. To tackle these through host plant resistance, a marker-assisted backcross breeding method was followed to pyramid a black rot-resistant gene (Xca1bo) and a downy mildew-resistant gene (Ppa3) from donors BR-161 and BR-2, respectively, into the background of Pusa Meghna cauliflower cultivar. Marker-assisted backcross breeding was followed up to BC2 generation using SCAR marker ScOPO-04833 and SSR marker BoGMS0624 for black rot and downy mildew resistance genes in foreground selection, respectively. In background selection, at each stage of backcrossing, 47 parental polymorphic SSR markers were used. The graphical genotyping of the five two-gene (Xca1boXca1boPpa3Ppa3) homozygous BC2F2 plants showed an average recovery of 85.44% of the Pusa Meghna genome with highest genome recovery of 91.7%. The genome contribution of donor parents (BR-161 and BR-2) was 8.26 with 6.34% of residual heterozygousity. The backcross derived pyramided lines BC2F2:3-7-16 and BC2F2:3-7-33 showed high resistance to both the diseases and exhibited higher yield and vitamin C content as compared with recipient parent Pusa Meghna. It is, therefore, evident from this study that resistant genes can be introgressed successfully into a Pusa Meghna cultivar without any yield penalty, benefitting farmers with reduced input cost and consumers with chemical residue free produce. Besides, the pyramided lines carrying dominant resistant genes can be exploited in a hybridization programme to develop hybrid(s) in cauliflower.

Recurrent parent phenome recovery analysis in six different populations with the introgression of genetic male sterile gene ms10 from hot pepper to heat tolerant bell pepper

Backcrossing is one of the most commonly used breeding methods to transfer target trait(s) into a bell pepper inbreds. We attempted for the first time to transfer genetic male sterile (GMS) ms10 gene from the donor parent MS-12, popular GMS line in India, into the genetic background of six heat tolerant bell pepper inbreds, in restricted generations through the marker-assisted selection (MAS) and backcross breeding method, to develop new GMS lines in bell pepper. In this project, the recurrent parent phenome (RPP) recovery was analyzed in each generations of backcrossing using economic phenotypic markers. Phenotypic background analysis revealed that the extent of RPP recovery ranged from 43.59% (MSSM-1) to 66.26% (MSSM-21) and 70.89% (MSSM-17) to 92.09% (MSSM-21) for fruit weight, from 19.0% (MSSM-21) to 55.14% (MSSM-3) and 61.0% (MSSM-21) to 98.75% (MSSM-1) for number of lobes fruit− 1, from 55.77% (MSSM-17) to 94.25% (MSSM-2) and 69.83% (MSSM-17) to 98.26% (MSSM-3) for total fruit yield plant− 1 in BC1F1 and BC2F1 populations, respectively. Based on a paired 't' test analysis in BC2F1 population, out of six, the MSSM-1 and MSSM-2 generation was shown to be non-significant for all 19 studied traits followed by MSSM-3 (18), indicating a successful recovery of the recipient genome through marker-assisted backcross breeding after successful introgression of the ms10 gene. The GMS lines developed from this project will be utilized in bell pepper breeding programs aimed to identify the best cross-combination for their cultivation under north-Indian plains.

Marker-Assisted Backcross Breeding for Improvement of Submergence Tolerance and Grain Yield in the Popular Rice Variety ‘Maudamani’

Submergence stress due to flash floods reduces rice yield drastically in sensitive varieties. Maudamani is a high yielding popular rice variety but is highly susceptible to submergence stress. The selection of progenies carrying Sub1 and GW5 (wide-grain) enhanced the submergence stress tolerance and grain yield of theMaudamani variety by following the marker-assisted backcross breeding method. Foreground screening detected 14 BC1F1, 17 BC2F1, and 12 BC3F1 backcross progenies that carried the target QTLs for submergence tolerance and grain width. Background screening was performed in the progenies carrying the target QTL and enhanced the recovery of a recipient parent’s genome by upto 96.875% in the BC3 pyramided line. The BC3F1 plant containing the highest recipient parent genome content and the target QTLs was self-pollinated. In BC3F2 generation, the target QTLs the Sub1 and GW5 (wide-grain) alleles and recipient parent’s yield component QTL OsSPL14 were tracked for homozygous states in the progenies. Seven pyramided lines showed tolerance to submergence for 14 days and higher grain yield than both the parents. The pyramided lines were similar to the recipient parent for the majority of the studied morphological and quality traits. The pyramided lines are useful as cultivars and can serve as potential donors for transfer of Sub1, OsSPL14, Gn1a, GW5 (wide-grain), and SCM2 QTLs.

Marker-Assisted Backcross Breeding for Improvement of Submergence Tolerance and Grain Yield in the Popular Rice Variety, ‘Maudamani’

Background: Submergence stress due to flash flood reduces rice yield drastically in sensitive varieties. Maudamani is a high yielding popular rice variety but highly susceptible to submergence stress. The Sub1 and yield component QTL, GW5 were transferred into the popular high yielding variety for enhancing submergence tolerance and yield. Methods: Sub1 and GW5 QTLs were transferred into Maudamani variety by adopting marker-assisted backcross breeding method. The target QTLs were selected by foreground selection in each backcross generation progenies to track the target QTLs. Recipient parent’s genome recovery was accelerated by adopting background selection in each backcross generation progenies carrying the target QTLs. Results: The two target QTLs were tracked in each backcross generation progenies by employing the tightly linked and direct markers. Background screening was performed in each backcross generation progenies carrying the target QTLs by using 57 background markers for enhancing the recovery of recipient parent’s genome content. The selected progenies containing highest genome recovery of the parent was hybridized with recipient parent, Maudamani. Finally, the selected BC3F1 plant containing highest recipient parent genome content and the two target QTLs was self-pollinated. In BC3F2 generation, two QTLs, Sub1 and GW5 along with recipient parent’s yield component QTLs, OsSPL14, Gn1a and SCM2 were tracked for their homozygous state in the progenies. Amongst the developed pyramided lines, six lines showed tolerance to submergence for 14 days and also exhibited higher grain yield than both the parents. The pyramided lines, MSS 607-116-541-117 and MSS 607-116-541-436 produced >9 t/ha grain yield showing an advantage of >5% over the popular recipient variety. Few pyramided lines were similar in appearance and quality traits with the recipient parent. Conclusion: The pyramided lines will be useful as potential donors for the QTLs Sub1+ OsSPL14+ Gn1a + GW5 + SCM2 and also as cultivars.

Introgression of qDTY1.1 Governing Reproductive Stage Drought Tolerance into an Elite Basmati Rice Variety “Pusa Basmati 1” through Marker Assisted Backcross Breeding

Drought stress at the reproductive stage in rice is one of the most important cause for yield reduction, affecting both productivity and quality. All Basmati rice varieties, including the popular cultivar “Pusa Basmati 1 (PB1)” is highly sensitive to reproductive stage drought stress (RSDS). We report for the first time, improvement of a Basmati cultivar for RSDS tolerance, with the introgression of a major quantitative trait locus (QTL), “qDTY1.1” into PB1. The QTL was sourced from an aus variety, Nagina 22 (N22). A microsatellite (simple sequence repeat (SSR)) marker “RM 431” located at telomeric end (38.89 mb) of chromosome 1, and located within a 1.04 mb QTL region was employed for foreground selection for qDTY1.1 in the marker assisted backcross breeding process. A set of 113 SSR markers polymorphic between N22 and PB1 were utilized for background selection to ensure higher recurrent parent genome recovery. After three backcrosses followed by five generations of selfing, eighteen near isogenic lines (NILs) were developed, through combinatory selection for agro-morphological, grain and cooking quality traits. The NILs were evaluated for three consecutive Kharif seasons, 2017, 2018 and 2019 under well-watered and drought stress conditions. RSDS tolerance and yield stability indicated that P1882-12-111-3, P1882-12-111-5, P1882-12-111-6, P1882-12-111-7, P1882-12-111-12, P1882-12-111-15 and P1882-12-111-17 were best in terms of overall agronomic and grain quality under RSDS. Additionally, NILs exhibited high yield potential under normal condition as well. The RSDS tolerant Basmati NILs with high resilience to water stress, is a valuable resource for sustaining Basmati rice production under water limiting production environments.