Adaptation and environmental sensitivity of mungbean genotypes evaluated in the international mungbean nursery

Summary Yield data from the 5th–12th international mungbean nursery (IMN) trials conducted at 23 sites in 15 countries were analyzed by conventional stability analysis—regression of genotype mean on the environmental index, and by segmented regression analysis—fitting separate linear regressions in low yielding and high yielding environments. The gene pool base concept allows comparison of genotypes from different IMN trials grown in different years and sites. A very high positive linear relationship was observed between the regression coefficient and the average yield of cultivars, indicating that high yielding cultivars were less stable across environments. When data points of the regression of genotype mean and site mean for VC 1973A, a high yielding and widely adapted cultivar, were examined, the relationship appeared not to be linear. The segmented regression analysis improved the coefficient of determination (r²) and the genotypes were grouped based on regression coefficients in high yielding and low yielding environments. Different categories of genotypes suitable for high input environments, widely adaptable genotypes, and highly stable genotypes were identified.Texas Agricultural Experiment Station Technical Article 23208.     

Selection environment and environmental sensitivity in barley

Summary Groups of 10 barley genotypes were selected for high grain yield under either high yielding (two groups) or low yielding conditions (two groups). The genotypes had a similar average grain yield across a wide range of yielding conditions, but differed in their linear response over environments (environmental sensitivity). The genotypes selected for high grain yield under low yielding conditions were less sensitive to changing environments than genotypes selected for high grain yield under high yielding conditions. The higher stability of genotypes selected under low yielding conditions was shown by both the linear regression analysis and the comparison of coefficients of variation. The use of a safety-first index showed that the probability of a crop failure of genotypes selected for high grain yield under high yielding conditions was between 1.8 and 2.7 times higher than for genotypes selected for high grain yield under low yielding conditions. The development of new cultivars for areas where a large proportion of the crop is grown by subsistence farmers should therefore be based on selection under low yielding conditions.     

Genotype × environment interaction for yield and reaction to leaf spot infections in groundnut in semiarid West Africa

Capitalizing on the yield potential in available groundnut germplasm, and high stability of kernel yield are important requirements for groundnut producers in semiarid environments. Forty-seven groundnut genotypes were evaluated from 2003 to 2005 at 4 locations representative of the Guinea and Sudan savanna ecologies in Ghana. The objectives were to assess genotypic differences in reaction to early and late leaf spot infections under natural field conditions, assess the extent of genotype × environment (G × E) interaction for kernel yield, and determine the relationship between yield potential and yield stability. Genotypes differed significantly in their reaction to leaf spot infections indicated by the area under disease progress curve (AUDPC). Genotypic AUDPC was negatively correlated with maturity period (P < 0.01), with kernel yield (P < 0.05) at each of the 3 locations in the Guinea savanna ecology but not in the Sudan savanna ecology and with each of four stability parameters (P < 0.05). High or low yielding genotypes were grouped based on Dunnett’s test at P < 0.10. High yielding groups had significantly low AUDPC, high biomass, high partitioning of dry matter for kernel growth, and were later in maturity compared to low yielding genotypes. Significant G × E interaction effect for kernel yield was dominated mainly by the lack of correlation among environments variance (76–78%) relative to the heterogeneity of genotypic variance component (22–24%). Stability of yield assessed through the among-environment variance, Wricke’s ecovalence, and Finlay-Wilkinson regression coefficient revealed that genotypes in the higher yielding group were relatively unstable compared to the low yielding group. Indicated by the Kataoka’s index of yield reliability, however, relatively unstable genotypes in the high yielding group are expected to be more productive even under assumptions of high risk aversion (P = 0.75–0.95) compared to the more stable, low yielding genotypes. The findings indicate that deploying these recently developed germplasm in semiarid regions in West Africa provides a better match to farmers’ risk-averse strategies compared with the use of existing earlier maturing cultivars.     

Studying the effect of environmental variables on the genotype × environment interaction of tomato

Genotype × environment interaction (GEI) affects marketable fruit yield and average fruit weight of both hybrid and open-pollinated (OP) tomato genotypes. Cultivars vary significantly for marketable fruit yield, with hybrid cultivars having, on average, higher yield than OP cultivars. However, information is scanty on environmental factors affecting the differential response of tomato genotypes across environments. Hence, the aim of this research was to use factorial regression (FR) and partial least squares (PLS) regression, which incorporate external environmental and genotypic covariables directly into the model for interpreting GEI. In this research, data from an FAO multi-environment trial comprising 15 tomato genotypes (7 hybrid and 8 OP) evaluated in 18 locations of Latin America and the Caribbean were analyzed using FR and PLS. Environmental factors such as days to harvest, soil pH, mean temperature (MET), potassium available in the soil, and phosphorus fertilizer accounted for a sizeable portion of GEI for marketable fruit yield, whereas trimming, irrigation, soil organic matter, and nitrogen and phosphorus fertilizers were important environmental covariables for explaining GEI of average fruit weight. Locations with relatively high minimum and mean temperatures favored the marketable fruit yield of OP heat-tolerant lines CL 5915-223 and CL 5915-93. An OP cultivar (Catalina) and a hybrid (Apla) showed average marketable fruit yield across environments, while two hybrids (Sunny and Luxor) exhibited outstanding marketable fruit yield in high yielding locations (due to lower temperatures and higher pH) but a sharp yield loss in poor environments. Two stable hybrid genotypes in high yielding environments, Narita and BHN-39, also showed high and stable yield in average and low yielding environments.     

Introgression of resistance to late blight (Phytophthora infestans) from Solanum pinnatisectum into S. tuberosum using embryo rescue and double pollination

In order to investigate the agricultural potential of the genus Vicia, and identify traits associated with productivity and responsiveness to environment, 34 undomesticated Mediterranean accessions representing Section Narbonensis (V. johannis, V. narbonensis) and V. sativa were grown in five contrasting environments in northern Syria (growing season rainfall: 76–290 mm).Highly significant genotype × environment interactions were observed for all traits. For most of the components of yield, accession mean performance (productivity)was highly correlated with responsiveness across environments (r = 0.59–0.96), as defined by joint linear regressions. Thus high yielding genotypes tended to be relatively more productive than low yielding genotypes under conditions that favoured high yields. Regression analysis revealed that mean site yields were positively correlated to rainfall (r = 0.85) and its attendant effect on growing season length as measured by cumulative season temperature and phenology (r = 0.59–0.81).In order to examine yield related traits independently of taxonomy, genotypes were grouped into three categories using K-means clustering based on productivity and responsiveness of seed, hay and biological yield. Highly productive/responsive genotypes were tall with high harvest index, large seeds and low fecundity (seeds and pods per plant), whereas unproductive/unresponsive plants tended to be short, highly fecund, with small seeds and low harvest index. Principal components analysis showed that responsiveness, in terms of seed, hay and biological yields, was closely related to phenological plasticity. Thus highly productive/responsive genotypes were able to start flowering earlier than unproductive/unresponsive genotypes in early environments, but significantly later in late, higher rainfall environments. Plant growth habit was also related to yield responsiveness. In environments with little biomass production the proportion of erect plants was high in all three categories. In more favourable, high biomass environments, the proportion of erect plants in unproductive/unresponsive genotypes fell dramatically, but was unchanged among productive/responsive genotypes. We suggest that for unproductive/unresponsive genotypes competition for light is increased under optimal growth conditions. We argue that the optimal combination of fixed and responsive traits in high yielding genotypes results in a `compound interest-type' response to more favourable environments. Highly productive and responsive genotypes can capture resources more effectively than their low yielding counterparts, leading to a positive relationship between performance and responsiveness for most components of yield. Differences in productivity and responsiveness for seed, hay and biological yield reflected Vicia taxonomy, increasing in the following order from low to high: V. johannis, V. sativa, the small seeded V. narbonensis (salmonea, jordanica, affinis) V. n. var. narbonensis, and finally V. n. var.aegyptiaca. V. n. var. aegyptiaca showed the most agricultural potential, since the taxon contained all the properties of productive/responsive genotypes listed above, yielding >1 t/ha under extremely arid conditions (104 mm),and >2.5 t/ha on 290 mm rainfall, confirming its potential for dry environments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pattern analysis on grain yield performance of Chinese and CIMMYT spring wheat cultivars sown in China and CIMMYT

Understanding the relationships among testing environments is essential for better targeting cultivars to production environments. To identify patterns of cultivar, environment, cultivar-by-environment interactions, and opportunities for indirect selection for grain yield, a set of 25 spring wheat cultivars from China and the International Maize and Wheat Improvement Center (CIMMYT) was evaluated in nine environments in China and four management environments at CIMMYT in Cd. Obregon, Mexico, during two wheat seasons. Genetic background and original environment were the main factors influencing grain yield performance of the cultivars. Baviacora M 92, Xinchun 2 and Xinchun 6 showed relatively more stable and higher grain yields, whereas highly photoperiod sensitive cultivars Xinkehan 9, Kefeng 6 and Longmai 19 proved consistently inferior across environments, except in Harbin and Keshan, the two high latitude environments. Longmai 26, also from high latitude environments in the north-eastern Heilongjiang province, was however probably not as photoperiodicly sensitive as other cultivars from that region, and produced much higher grain yield and expressed a broader adaptation. None of the environments reported major diseases. Pattern analyses revealed that photoperiod response and planting option on beds were the two main factors underlying the observed interactions for grain yield. The production environment of planting on the flat in Mexico grouped together with Huhhot and Urumqi in both wheat seasons, indicating an indirect response to selection for grain yield in this CIMMYT managed environment could benefit the two Chinese environments. Both the environment of planting on the flat with Chinese Hejin and Yongning, and the three CIMMYT environments planting on raised beds with Chinese Yongning grouped together only in one season, showing that repeatability may not be stable in this case.     

Genotype × environment interactions for tea yields

Several methods were used to evaluate phenotypic stability in 20 tea (Camellia sinensis) genotypes, many of which are cultivated widely in East Africa. The genotypes were evaluated for annual yields at two sites over a six year period. Data obtained were used to compare methods of analysis of G × E interactions and yield stability in tea. A standard multi-factor analysis of variance test revealed that all first order interactions (genotypes × sites; genotypes × years; sites × years) as well as second order interactions (sites × genotype × years) were significant. Regression analysis was used to assess genotype response to environments. Regression coefficients (b_i) obtained ranged from 0.78 to 1.25. Deviations from regression (S²d) were significant (p < 0.05) from 0.0 for all the test genotypes. Analysis for sensitivity to environment change (SE² _i) revealed that the test genotypes differed in their level of sensitivity. The hierarchical cluster analysis method was used to assemble the test genotypes into groups with similar regression coefficients (b_i) and mean yield, which proved useful for the identification of high yielding genotypes for breeding purposes as well as for commercial exploitation. Rank correlation between yield and some stability parameters were significant. Mean yield was significantly correlated to b_i (r = 0.80^***) and SE² _i(0.74^***) which is an indication that selection for increased yield in tea would change yield stability by increasing b_i and SE² _i leading to development of genotypes that are specifically adapted to environments with optimal growing conditions. Genotypes differed in response to years and sites. As stand age increased, genotype yields generally increased though annual yield fluctuations were more pronounced in some genotypes than others. This response was not consistent across the sites for all genotypes indicating the need to test clones at multiple sites over longer periods of time. This revised version was published online in August 2006 with corrections to the Cover Date.     

Assessment of mungbean genotypes for durable resistance to Yellow Mosaic Disease: Genotype × Environment interactions

Yellow mosaic disease (YMD) is the major constraint of mungbean for realizing high productivity worldwide. Moreover, management of disease using YMD‐resistant genotypes is the simplest approach. Therefore, based on a preliminary screening of 220 genotypes during the year 2010 and 2011 at 17 locations, a set of 25 genotypes was further selected to evaluate at six locations over 2 years for identification of more stable resistant genotypes. The genotype and genotype × environment (GGE) analysis indicated that the genotypes and environment effects were significant (P < 0.001) for YMD incidence. Interestingly, the GGE biplot analysis successfully accounted for 74.71 per cent of the total variation with three genotypes (ML 818, ML 1349 and IPM 02‐14) showing high degree of resistance and stability over the locations. Notably, a strong positive association was observed between disease reaction and temperature, relative humidity and rainfall. As crop is grown in diverse growing environments, aforementioned genotypes can be used as stable/durable sources for future breeding programme to develop YMD‐resistant cultivars.     

Effects of Temperature and Frost on Genotypes of Medicago truncatuh L. and Medicago aculeata L. from Contrasting Climatic Origins

The growth of M. truncatula and M. aculeata genotypes collected from sites of contrasting altitudes and winter temperatures was compared under different temperature regimes. Genotypes collected from mild winter environments produced more shoot dry matter, had higher leaf area and lower specific leaf weight than those from cold environments; however these effects were largely related to seed size for M. aculeata. Only genotypes from mild environments were responsive to temperature.
Frost tolerance of the genotypes was tested using a laboratory freezing test based on seedling survival. There was a relationship between frost tolerance and winter temperature at site of collection for M. aculeata , with the most frost tolerant genotypes coming from high altitudes. All genotypes of M. truncatula demonstrated low survival rates following frost damage. Genotypes from high altitudes represent a promising source for breeding for first tolerance with greater variation m M. aculeata than M. truncatula.     

Simple approach to the analysis of GxE interactions in a multilocational spaced plant trial with timothy

Summary Sixty genotypes of timothy, comprising 12 genotypes originating from each of five locations, were grown at the same locations in northern Scandinavia and Iceland, as a part of a joint breeding project in timothy. The trials were observed for two years and various characters were evaluated. Large genotype x environment interactions occurred for most characters and the response of individual genotypes. irrespective of origin contributed most to the variation. A superiority measure (P.), based on the genotype's response and the maximum response, averaged over all locations, was used to rank the genotypes with respect to yield and other morphological attributes. Based on this ranking it is possible to choose genotypes which are high yielding and show good stability over the area.     

Genetic variation in drought tolerance at seedling stage and grain yield in low rainfall environments in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Genetic architecture of seedling drought tolerance is complex and needs to be better understood. To address this challenge, we developed a protocol to identify the most promising drought-tolerant genotypes at the seedling stage in winter wheat. A population of 146 recombinant inbred lines (F₉) derived from a cross between wheat cultivars, ‘Harry’ (seedling drought tolerant) and ‘Wesley’ (seedling drought susceptible) were used in this study. All genotypes were sown in three replications in a randomized complete block design under controlled conditions in a greenhouse. Seven traits were scored and grouped into tolerance traits; days to wilting, leaf wilting, and stay green and survival traits; days to regrowth, regrowth, drought survival rate, and recovery after irrigation. Three selection indices were calculated (1) tolerance index, (2) survival index, and (3) drought tolerance index (DTI). The same set of genotypes were also tested for grain yield in two low rainfall environments for two seasons. High genetic variation was found among all genotypes for all seedling traits scored in this study. Correlations between tolerance and survival traits were weak or did not exist. Heritability estimates ranged from 0.53 to 0.88. DTI had significant phenotypic and genotypic correlations with all seedling traits. Genotypes were identified with a high drought tolerance at the seedling stage combined with high grain yield in low rainfall. Breeding for tolerance and survival traits should be taken into account for improving winter wheat drought tolerance at seedling stage. The selected genotypes can be used for to further improve drought tolerance in high yielding wheat for Nebraska.     

Relationship between barley grain yield measured in low- and high-yielding environments

Summary The paper addresses the general question of identifying the optimum environment for selection in plant breeding programs for low input agricultural systems. After defining low-yielding and high-yielding environments based on the average grain yield of large numbers of barley genotypes in different cropping seasons, we examined: 1) the phenotypic relationships between the highest yielding genotypes in low- and high-yielding environments, and 2) the genetic correlation coefficients between grain yield in low- and high-yielding environments. The results indicate that the alleles controlling high grain yield in low-yielding conditions are at least partially different from those controlling high grain yield in high-yielding conditions. Therefore, selection in high-yielding environments is expected to produce a negative response or no response in low-yielding environments. This may explain why crop varieties bred under high-yielding conditions failed to have an impact in low-yielding agricultural systems. The results may be extrapolated to systems where environmental concern suggests a reduction of inputs by raising the question of whether crop breeding programs based on selection under high inputs are likely to generate the right type of germplasm for an environmentally friendly agriculture.     

Yield stability and adaptability of canola (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) in multiple environment trials

Selecting high yielding genotypes with stable performance is the breeders’ priority but is constrained by genotype × environment (G×E) interaction. We investigated canola yield of 35 genotypes and its stability in multiple environment trials (MET) in south-western Australia and the possibility to breed broadly-adapted high yielding genotypes. The Finlay–Wilkinson (F–W) regression and factor analytic (FA) model were used to investigate the G×E interaction, yield and genotype stability and adaptability. The cross-over response in the F–W regression, substantial genetic variance heterogeneity, and the genetic correlations in the FA model demonstrated substantial G×E interaction for yield. Cluster analysis suggests low, medium and high rainfall mega-environments. F–W regression indicated that genotypes with high stability (e.g. low regression slope values) produced relatively low yield and vice versa, but also identified broadly adapted genotypes with high intercepts and steep regression slopes. The FA model provided a more detailed analysis of performance, dividing genotypes by positive, flat or negative responses to environment. In general, early flowering genotypes responded negatively to favourable environments and vice versa for late flowering genotypes. More importantly, a few early flowering hybrids with long flowering phases were consistently productive in both low and high yielding environments, showing broad adaptability. These productive hybrids were consistent with those identified earlier by high F–W intercept and slope values. Hybrids were higher yielding and more stable than open-pollinated canola, as was Roundup-Ready^® canola compared to the three other herbicide tolerance groups (Clearfield^®, Triazine tolerant, conventional). We conclude that yield stability and high yield are not mutually exclusive and that breeding for broadly adapted high yielding canola is possible.     

Comparison of the resistance and susceptibility to downy mildew [<Emphasis Type="Italic">Hyaloperonospora parasitica</Emphasis>, constant. (Pers. Ex Fr)] of nine <Emphasis Type="Italic">Brassica olearacea</Emphasis> accessions in laboratory,seedbed, and field screens

The relationship between resistance in seedlings, young and adult plants is studied for the pathosystem Brassica oleracea–Hyaloperonospora parasitica. Genotypes identified in the laboratory as resistant or susceptible or exhibiting a differential reaction to a selection of H. parasitica isolates were tested in 1997–1999 in seedbeds and fields under natural infestation. Isolates tested in the laboratory were grouped in five pathotypes, of which four were presented by isolates from Brittany, France. Genotypes susceptible to all pathotypes in the laboratory were also susceptible in the seedbed and field tests, while genotypes expressing a differential response to pathotypes were either resistant or susceptible. Accessions Everest, DEGC, ESPG and RS1105 exhibiting resistance to all pathotypes except I, were resistant in all environments and remained resistant in 2000–2002. Pathotype I was not prevailing in the field and results support the hypothesis that accessions resistant under laboratory conditions will be resistant under field conditions, provided the same pathotypes are present under the laboratory and field conditions.     

Adaptation and yielding ability of castor plant (Ricinus communis L.) genotypes in a Mediterranean climate

Successful castor (Ricinus communis L.) cropping in Greece depends on the yielding ability and yield stability of the cultivars (hybrids or inbreds) as well as the reliability of production systems. The adaptation and yielding ability of 19 modern castor oil genotypes were studied for 3 years in two sites of Northern Greece. Genotypes combining high seed and oil yield and desirable morphological characteristics were tested for 2 or 3 years, whereas the rest were tested for 1 year only. The growing period in both locations was long enough for ripening the first raceme and a number of secondary racemes depending on the genotypes. The plant height was dependent mainly on the genotypes but also was affected by the site and the year of the experimentation and ranged from 79 to 278 cm. The seed yield varied between 2.5 and 5.0 Mg ha⁻¹, values that are among the highest reported in the literature. The seed yield was higher in the site where plants produced and ripened more secondary racemes. The seed oil content was dependent mainly on the genotype and ranged from 44.5 to 54.2%. The oil yield followed the changes in seed yield. The variation in seed yield between years was low and in most genotypes less than 20%. Results indicate that the castor oil crop was satisfactorily adapted in the area.     

Characterization of resistance of cassava genotypes to bacterial blight by evaluation of leaf and systemic symptoms in relation to yield in different ecozones

Twenty-two improved and local cassava genotypes were evaluated for their bacterial blight symptom types in reaction to infection by Xanthomonas axonopodis pv. manihotis under field conditions in the forest, forest savanna transition and wet savanna zones of Togo. High genotype × environment interactions in development of each symptom type were observed. Combining data on environments and genotypes, spot, blight and wilt symptoms were positively correlated. Analysing genotype reactions across environments, indications for independent mechanisms of resistance on leaf and stem level, varying by genotype, were found. Genotypes Main27 with resistance to spot and blight symptoms and TMS4(2)1425 with resistance to wilt symptoms are recommended to breeders to introgress their resistance characteristics. Significant negative correlations were generally observed between blight and wilt symptom development and root yield across ecozones, with blight being more important under lower, and wilt under higher inoculum pressure. Genotypes TMS30572, CVTM4, TMS92/0429 and TMS91/02316 showed low spot, blight and wilt symptoms combined with high root yield across ecozones.     

Physiological Responses and Dry Matter Partitioning of Summer Mungbean (Vigna radiata L.) Genotypes Subjected to Drought Conditions

Drought is the most important limitation to summer mungbean production in the tropics and subtropics dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with drought tolerance. However, there is little genotypic information on drought tolerance in summer mungbean. The objectives of this study were to assess the genotypic differences in physiological traits and dry matter partitioning in mungbean and to measure the association of these traits with crop performance under drought conditions. Six mungbean genotypes were tested in drought micro plots at CCS Haryana Agricultural University, Hisar, India. A split plot design was used; two irrigation treatments (watered and droughted) in the main plots and six mungbean genotypes in the subplots with three replicate micro plots. Drought decreased leaf water status, rates of photosynthesis (P_n) and altered dry matter partitioning in different plant parts. Our results showed that P_n did not limit yield, but it was partitioning of dry matter governed by leaf water content (RWC) which influenced the final yield. RWC was positively correlated to the number of pods per plant and seed yield, genotypes maintaining high RWC produced higher seed yield. Therefore, the drought tolerance of summer mungbean was related to the maintenance of high RWC, which can be used as a physiological marker to identify and develop superior genotypes suited to drought-prone environments.     

Non-parametric measures of phenotypic stability in chickpea genotypes (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.)

Multi-environment trials (MET) play an important role in selecting the best cultivars and/or agronomic practices to be used in future years at different locations by assessing a cultivar's stability across environments before its commercial release. Objective of this study is to identify chickpea (Cicer arietinum L.) genotypes that have high yield and stable performance across different locations. The genotypes were developed by various breeders at different research institutes/stations of Iran and the International Center for Agricultural Research in Dray Areas (ICARDA), Syria. Several statistical methods were used to evaluate phenotypic stability of these test chickpea genotypes. The 17 genotypes were tested at six different research stations for two years in Iran. Three non-parametric statistical test of significance for genotype × environment (GE) interaction and ten nonparametric measures of stability analyses were used to identify stable genotypes across the 16 environments. The non-parametric measures (Kubinger, Hildebrand and Kroon/Van der) for G × E interaction were highly significant (P < 0.01), suggesting differential responses of the genotypes to the test environments. Based on high values of nonparametric superiority measure (Fox et al. 1990) and low values of Kang's (1988) rank-sum stability parameters, Flip 94-123C was identified as the most stable genotype. These non parametric parameters were observed to be associated with high mean yield. However, the other nonparametric methods were not positively correlated with mean yield and were therefore not used in classifying the genotypes. Simple correlation coefficients using Spearman’s rank correlation, calculated using ranks was used to measure the relationship between the stability parameters. To understand the nature of relationships among the nonparametric methods, a hierarchical cluster analysis based on non weighted values of genotypes, was performed. The 10 stability parameters fell into three groups.     

Indonesian mungbean landraces II. Comparison of performance,components of variance and selection for grain yield under wide row-spacing in monoculture and when intercropped with maize

Summary The possibility of testing mungbean for grain yield in monoculture in single wide-spaced row plots as an alternative to selection in intercropping with maize was investigated. Results indicated no significant genotype x planting pattern interactions and genetic correlation coefficients between grain yields in the two planting patterns were, in most cases, close to unity. It was concluded that, as far as the mungbean component in the mixture is concerned, yield selection in either of the two planting patterns is justified. Effects of single-plant and progeny selection on mungbean characteristics were also studied empirically. Lines derived from single-plant selection in monocropping or intercropping showed differences in yield, number of pods per plant and seed weight. Except for seed weight, no differential effects of progeny selection in monoculture or intercropping were observed for any characteristic.     

Variation in sensitivity to streptomycin-induced bleaching and dark-induced senescence of rice (<Emphasis Type="Italic">O. sativa</Emphasis>) and ragi (<Emphasis Type="Italic">E. coracana</Emphasis>) genotypes and their relationship with yield and adaptability

Variation in streptomycin sensitivity and dark sensitivity of 36 rice genotypes of three different maturity groups and 30 ragi genotypes of two different maturity groups were studied. Streptomycin sensitivity and dark sensitivity of rice and ragi genotypes were expressed in terms of bleaching index (BI) and senescence index (SI), respectively. Genotypes of each maturity group of each crop showed wide variation in their BI / SI values. The objective of this investigation was to find the relationship of the BI / SI parameter with yield, adaptability, and stability in yield performance of rice and ragi genotypes. Yield performance of rice and ragi genotypes were evaluated over 12 and nine environments, respectively. Adaptability and stability analysis were done following the linear regression model of Eberhart and Russell (1966) and the AMMI Stability Value (ASV) of Purchase (1997). BI parameter showed a positive correlation with yielding ability and deviation from regression (S2d) in both rice and ragi, and a negative correlation with adaptability parameter (b) for all the maturity groups of rice and ragi except in the early ragi group. SI parameter showed a negative correlation with yielding ability for all the maturity groups of rice and ragi except in the early ragi group and a positive correlation with adaptability parameter (b) for all the maturity groups of rice and ragi. This experimental study revealed that sensitivity of rice genotypes to streptomycin (SM) in terms of BI could be used to predict yielding ability of genotypes, and dark sensitivity (SI) could be used to indicate adaptability to rich and poor environments. This novel approach may help the breeder in indirect selection of high-yielding genotypes and genotypes well-adapted to rich or poor environments at an early seedling stage before going for multilocation trials.