Effective breeding for economically important resistance to Sclerotinia trifoliorum Eriks in alfalfa (Medicago saliva L.) requires that the plant breeder have an understanding of any genetic basis for variability in measurements of resistance and the likelihood that selection for resistance to one isolate confers resistance to other isolates. Fifty alfalfa plants were repeatedly evaluated for their resistance to five isolates of S. trifoliorum. Tips of excised stems were inoculated with a S. trifoliorum isolate and stem necrosis was measured after 14 d. The inoculation of five stems from each of 50 plants with a single isolate was repeated five times. For the length of stem necrosis, the interaction of pathogen isolate and alfalfa plant was not significant but differences among alfalfa plants and among isolates were significant. The plants that, on average, developed larger necrotic regions did not have more or less variation in their replicated measurements of necrosis than those plants which averaged much smaller necrotic regions. The genotype of the alfalfa plant had a greater effect on the variability in replicate measurements of disease than the genotype of pathogen isolate. Resistance to different isolates were significantly correlated (r = 0.48–0.60) and selection of some plants for resistance to one isolate appeared to improve resistance to other isolates.

Sclerotinia crown and stem rot (SCSR) caused by Sclerotinia trifoliorum Eriks. is often a serious disease on alfalfa (Medicago sativa L.) during cool, wet periods of the year. No cultivars have been developed with increased resistance to this disease. This research determines the selection responses to one cycle of divergent selection for resistance to SCSR. Plants of four genetically different populations were evaluated for resistance to SCSR using a stem‐tip inoculation technique. Selectious were made at 4 and 8% selection intensities for both resistance and susceptibility. Selections were polyerossed to produce four experimental synthetics (two selected for resistance and two selected for susceptibility). Plants grown from seed of each experimental synthetic and from remnant seed from each source population were evaluated for resistance along with ramets of the parental plants of the synthetics. Experimental synthetics selected for resistance at selection intensities of 4 and 8% had necrotic regions 4.0 and 4.5 cm long, respectively. The experimental synthetics selected for susceptibility at intensities of 4 and 8% had necrotic regions 7.4 and 8,2 cm long, respectively. Means of each of the experimental synthetics were significantly different (P 0.05) from the mean (6.1 cm) of the unselected population. Ileritability was estimated at 0.49 (SE = 0.14) using a regression of offspring parent. Resistance to Sclerotiula is heritable and can be increased or decreased using the stem‐tip inoculation technique.

Submergence stress due to unpredictable soil flooding is one of the main constraints encountered in rainfed growing areas, especially in Southern Sumatran riparian swamps. The development of submergence-stress-tolerant cultivars through the introgression of Sub1 via marker-assisted backcrossing (MABC) is an ideal solution. This study was carried out during 2020 at Sriwijaya University, Palembang, Indonesia, with the aim to select Sub1-introgressed lines in BC3F1 generations on the basis of MABC and to screen out the SSR markers that were unlinked to the target gene for application in subsequent background selection studies. Results revealed that almost all the backcrossed progenies segregated from the rice parental cultivars ‘FR13A’ and ‘Pegagan’. The backcrossed lines showed significantly improved submergence stress tolerance and recovery rates compared with their parents. Sub1 introgression into the BC3F1 generation was confirmed by the tightly linked Sub1 marker SUB1C173, and marker RM23915 was used for recombinant selection. These markers followed the expected marker segregation ratio in accordance with the Mendelian single gene model. In the parental polymorphism survey, 84 out of 237 SSR markers that were unlinked to the target loci were found to be available for background study. Twenty-seven backcrossed lines were selected on the basis of foreground selection. Seven plants were selected on the basis of the recombinant marker RM23915. Five backcrossed lines were further selected on the basis of submergence stress tolerance and agronomic performance.

Yield and quality of some local black rice cultivars were low as the panicle in the same clump do not reach maturity at the same time. This research program utilized plants of three local black rice cultivars of "Mariana", "Purwokerto", and "Toraja". The plants were planted in pots and placed under a plastic house. Some agronomic traits were measured, including number of productive tiller (NPT) and NPT with mature grains in the panicle>85% (NPT-85). Selected plants were determined by quadrant method of NPT-85 over NPT. After three selection cycles, the research reveals four potential accessions of 17,21,28), 15,23,33); 23,27), and Toraja-06.07 (11,13,19). These four accessions called as Unsri P-1 to Unsri P-4, respectively. Field evaluation indicated, the accessions were able to produce high quality grain with NPT-85 over NPT ratio ranged from 87% to 95 %, and yield potential ranged from 6.16 to 8.81 dry un-hulled grain t/ha.

A stem-tip inoculation procedure has been successfully used in divergent selection for resistance to Sclerotinia trifoliorum (Eriks) on alfalfa (Medicago saliva L.). One unreported observation made in early studies was that lesion development was not continuous for some alfalfa plants over the 14-d incubation. A more in-depth study of disease development was needed to quantify the variability, and the stem-tip inoculation procedure was modified for this purpose. Inoculated stems were placed in plastic sleeves and marks were made daily on the plastic to show the development of necrosis over time. Eight plants previously selected for their higher levels of resistance and eight plants selected for minimal resistance (susceptibility) developed necrosis after 14 d in the plastic sleeves, which was similar to that measured in earlier studies. The length of the lesion on susceptible plants was described by a linear equation with 0.9 to 1.3 cm of necrosis d i. Six of the resistant plants stopped the lengthening of the necrotic stem lesion about 8 d after inoculation while two of the resistant selections continued linear development at rates much less than that measured on the susceptible selections. When the necrotic region stopped developing, a dark border usually developed between the green and necrotic tissues which was not seen when disease continued to develop. Statistical analysis suggested disease resistance might be effected by either of two qualitatively different systems.