Greenhouse screening using infested toothpicks was compared to field evaluation of soybean [Glycine max (L.) Merr.) breeding lines for resistance to stem canker disease, caused by southern strains ofDiaporthe phaseolorum (Cke. & E11. (Sacc.) var. caulivora Athow and Caldwell (Dpc). Field screenings are reliable indicators of resistance, but often the disease does not develop naturally in field screening nurseries. Thirty‐seven random F4:6 lines from the cross ‘Hutton’ (susceptible ) ✕ ‘Tracy M’ (resistant) were evaluated for their reaction to Dpc in the field (two locations, 2 yr) under natural infestation and infection conditions, and in the greenhouse (three experiments) with artificial inoculation using infested toothpicks. Our objectives were to compare field and greehouse screening and to determine the usefulness of greenhouse inoculation in predicting the yield and disease reaction of breeding lines when these lines were subjected to natural field infection conditions. Field screening based on symptoms and yield was highly effective in identifying resistant genotypes. Heritabilities for yield and disease ratings in the field were 87 and 92%, respectively. The toothpick inoculation procedure used in the greenhouse was effective with each of three Dpc isolates (different in geographic origin from the field location) in identifying the genotypes that showed highest levels of disease resistance in the field. Phenotypic correlations between greenhouse ratings and yield in the infested field ranged from −0.71 to −0.61. Results indicated that selection based on greenhouse screening can be an effective alternative to field screening when resistance is derived from Tracy M.

http://aasj.bu.edu.eg/index.php Combining ability analysis using diallel crosses among seven inbred lines of corn under two sowing dates.

This work aimed at studying earliness, yield and photosynthetic parameters in some local and exotic rice resources. Twelve rice entries were used in the study including two from Bangladesh, one from Madagascar, three from Egypt, two from Korea and four from IRRI. These genotypes were evaluated during 2020 and 2021 seasons in RCBD using four replications at the Faculty of Agriculture, Moshtohor Experiment Station. Significant differences were found among rice entries for all studied traits in the two growing seasons. The genotype GZ 10686-1-2-2-1 was the earliest among all studied entries, while genotype PR 78 was the shortest among all entries. Entry IRRI 142 had the highest significant value for chlorophyll content comparing to Giza 179, panicle length was highest with the genotype SAIBORO 9361. The genotype Korea 27 expressed the best mean values for panicle weight, weight of 100 grain and grain yield plant -1 , while genotype IRRI 152 ranked the second best for grain yield plant -1 . Genotype GZ 10848-1-2-2-1 was the best for number of tillers plant -1 . Moreover, the genotype IRRI 152 exhibited the most desirable mean values for cuvette temp. and leaf diffusive, while genotype Korea 27 was the best for quantum sensor, stomatal conductance and Co2 assimilation rate in both seasons. For transpiration rate, the genotype AC 2882 expressed the best mean value, while Korea 47 gave the lowest value for this trait with significant difference from the variety Giza 179.

Five rice lines and three testers were crossed in line x tester mating design and the resultant fifteen hybrids along with their eight parents were evaluated under normal and drought conditions (irrigation every 12 days). This investigation was undertaken at the experimental farm of Rice Research and Training Center (RRTC), Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt during 2019 and 2020 growing season. Genetic diversity, combining ability, heterosis, and antioxidant enzymes were studied. Four primers were used to study genetic diversity. The results revealed a total number of 7 alleles were ranged from one to three alleles per locus, the average of major allele frequency, gene diversity, and (PIC) were 0.607, 0.45, 0.46), respectively. The GD dendrogram revealed the close similarity among the genotypes; IET 1444, GZ1368 and G177 clustered together in the main cluster. On another hand, NP856-9 diverged in sub cluster and the other genotypes G178, G179, A22, and G182 were clustered together. The drought had an intensive inhibition on studied traits, plant height, chlorophyll content, grain yield plant-1 and 1000 grain weight. Otherwise, all genotypes were more earliness under drought than under normal. Highly significant differences were detected among genotypes and their partitions for all studied traits. Both additive and non-additive are important in the inheritance of studied traits. The parents GZ 1368 under normal irrigation and combined data and IET 1444 under stress condition seemed to be the best combiner for grain yield plant-1. The cross NP856-9 X GZ 182 revealed the highest significant and positive SCA effects for chlorophyll content and grain yield/plant. The most desirable midparent and better-parent heterosis for grain yield plant-1 were detected for the crosses IET1444 x G182 and NP856-9 x G182, respectively in the combined data. Results indicated that the activity of antioxidant enzymes: CAT, APX, SOD, and MDA enhanced under drought conditions. Similarly, proline accumulation increased due to water stress.

This investigation was conducted at Agriculture Research station, Sakha, Kafr El-sheikh, Egypt during 2019 and 2020 rice seasons to study genetic diversity, combining ability and photosynthetic parameters in rice. A line x tester model was used in this study where five rice varieties were crossed with three testers. Four primers were used to estimate the genetic diversity of the studied paternal lines and the values of major allele frequency ranged from 0.62 to 0.75 and averaging 0.69. Genetic diversity values ranged from 0.37 to 0.47 and averaging 0.42. The PIC values ranged from 0.43 to 0.61 and averaging 0.52. The GD dendrogram classified the studied rice genotypes into two main clusters: The first cluster included Giza 178 and Sakha 108, while the second cluster included the other genotypes. Genetic distance ranged from 0.147 to 0.886 and the highest genetic distance was observed between Giza 182 and Sakha 178. Highly significant differences were detected among genotypes and their partitions for all studied traits. The highest mean values were detected for the crosses Sakha 107 x Sakha 101 for earliness as well as Sakha 108 x Sakha 101 and Giza 182 x Giza 179 for grain yield plant -1 . The mean squares due to SCA were much higher than those of GCA for all studied traits, indicating that the studied traits were governed by non-additive gene action. The parent Sakha 107 expressed the highest significant and negative gca effects for days to 50% flowering. Parent Sakha 108 seemed to be the best general combiner for grain yield plant -1 . The most desirable SCA effects for days to 50% flowering were detected for the cross Sakha 108 x Sakha 101, while the cross Giza 182 x Giza 179 expressed the most desirable SCA effects for grain yield plant -1 . The most desirable mid-parent and better-parent heterosis values were detected for the cross Sakha 107 x Sakha 101 for days to 50% heading and the cross Sakha 108 x Sakha 101 for grain yield plant -1 . The cross Sakha 108 x Sakha 101 expressed the highest mean values of cuvette temperature, leaf diffusive, net assimilation rate and stomatal conductance, while the cross Sakha 107 x Giza 179 gave the best values for transpiration rate.