Identification of Striga Resistance in Sorghum Landraces From Eritrea Using Molecular and Invitro Methods

Abstract

Striga hermonthica is the main biological constriant hampering sorghum output in several regions of sub-Saharan Africa including Eritrea. Striga hermonthica, endemic parasitic weed of sub-Saharan Africa is steadily increasing its geographic distribution and level of infestation, and thereby reducing crop yield. Striga attaches itself to the host crop's roots, causing serious damage and reduced yield. Utilization of sorghum genotypes which are resistant to Striga is the best practical and economical method of dealing with the Striga problem. The study's aims were as follows: 1) To determine farmers’ views on sorghum production constraints; opportunities; Striga incidence and extent in sorghum growing area of Eritrea. 2) To find out the levels of stimulants for Striga germination in sorghum landraces and their derivatives. 3) Select for Striga resistance in sorghum landraces from Eritrea using polymorphic SSR markers. 4) To determine at gene level, the differential expression of Striga resistance in a Striga vulnerable and resistant genotypes of sorghum. In order to achieve the first objective, 136 farmers from the Eritrean subzones of Golij, Tesenei, and Hamelmalo were interviewed. The interviews were conducted utilizing semi structured questionnaire and small-group discussions in order to understand the difficulties that the research area's sorghum production faces. Crops such as sorghum, sesame, pear millet, and groundnut were the major significant cereal crops in the research area. More than 80% of the respondents in the surveyed area indicated that drought stress as the most significant limitation to sorghum output, followed by infestation of Striga. Most of the interviewed farmers (81.6%) stated that Striga affected their sorghum farm and the degree of damage it inflicted varied from one subzone to another raging from mild (10%) to severe (70% and above). When it came to choosing xvi sorghum cultivars, local farmers said increased crop output, tolerance to drought, and resistance to Striga were the major essential factors. In the research area, up to 31 diverse landraces were identified as the most prevalent. Local varieties saved by farmers from past harvests were the most common source of seed for production. To determine the levels of stimulants for Striga germination in sorghum from Eritrea, the resilience of 111sorghum local varieties and their derivatives were evaluated using the capability of genotypes of sorghum to effect germination of Striga seed as a measure of the amount of germination stimulant generated. The number of germinated Striga seeds was counted, and the germination percentage for Striga was calculated. Sorghum accessions EG830, EG1076, EG473, EG1261, EG546, and EG746 were reported to produce low levels of Striga germination, with 11.85 %, 13.05 %, 14.68 %, 15.32 %, 15.74 %, and 16.5 % germination percentages, respectively, when compared to controls, IS9830, SRN39, and Framida, which had 22.46%, 22.67%, and 23.27%. Despite the fact that these accessions did not demonstrate total resistance to Striga seed germination, the low amount of stimulant production showed that they had a high level of Striga resistance. The findings suggested that the germplasms identified could be exploited in sorghum breeding efforts as viable options of Striga infection resistance. Laboratory studies using SSR markers aimed at investigating the presence of Striga resistance QTLs in 92 landrace sorghum accessions indicated that 8 genotypes have shown one to three Striga resistance QTLs. Accessions containing one or more Striga resistance QTLs were further evaluated in pot experiment. The results indicated that accessions EG1075, EG1168, and EG1239 have shown lesser number of Striga count and better grain yield compared to the other genotypes tested implying better resistance to Striga.