Summary of composite and variety trials ICRISAT Pearl Millet Breeding 1977-1986

The purpose of this report is to provide information on the objectives, materials and methods, and status of statistical analysis of ICRISAT trials involving composites and varieties of pearl millet. The documentation of this information mill aid interpretation and combined analyses of previous experiments..

Early-maturing dual-purpose sorghums: Agronomic trait variation and covariation among landraces

Landrace cultivars represent potentially valuable source material for breeding dual-purpose (grain and stover) sorghums. To characterize the genetic variation and interrelationships for major agronomic traits among potential dual-purpose sorghum landraces, 74 accessions, primarily from Southern Africa, the Sudan, and India, were evaluated in five environments at Patancheru, India. These environments, at 17°N with 520-540 mm rainfall during the growing season, are representative of the major sorghum-growing areas in India and the Sudanian Zone of Western and Central Africa. Significant genetic variation and high heritabilities (P = 0.01, h2= 0.63-0.92) were observed for seedling vigour, grain and stover yields, growth rate and harvest index. Time to flower was correlated with stover yield (r = 0.48, P = 0.01) and an index (Iev) of total economic value (r = 0.44, P = 0.01) but not with grain yield (r = 0.22, P = 0.05). Grain and stover yields varied independently (r = 0.22, P = 0.05) and were similarly related to Iev, values (r = 0.79 and r = 0.77 (P = 0.01), respectively). The 13 landraces with the highest Iev values (adjusted for maturity) had above-average growth rates and harvest indices that ranged from 20 to 38%. Landraces from Botswana and India were more highly represented in the high Iev set than in the full set of accessions

Recurrent Selection for Increased Grain Yield and Resistance to Downy Mildew in Pearl Millet

Six pearl millet (Pennisetum glaucum [L.] R. Br.) composites were subjected to three or more cycles of selection in multilocational yield trials and downy mildew disease nurseries in India. The base and selected populations were tested (a) over four years at three locations in India (11° to 29°N), (b) under terminal-drought and optimal moisture conditions for two years, and (c) under induced downy mildew infections to determine the impacts of selection on grain yield, agronomic traits, and resistance to downy mildew (Sclerospora graminicola Sacc. Schroet.). Mean grain yield increases for four composites undergoing three to six cycles of selection ranged between 23 to 94 kg ha-1 cycle-1 (0.9 to 4.9 % cycle-1) which, averaged over composites, amounted to 3.3 % cycle-1. Yield gains were generally expressed at all test locations and under both terminal-drought and optimal moisture environments. The gains in grain yield were associated with increases of both biomass and harvest index without extending the growth duration except in the earliest composite. Susceptibility to downy mildew remained below 10 % in all selected populations. Thus, the effectiveness of recurrent selection for increasing yield and yield stability of pearl millet is clearly demonstrated

Biometrical analysis of alternative plot types for selection in rye

Maximizing the efficiency of selection for yield and baking quality of winter rye (Secale cereale) requires reliable knowledge of the pertinent population parameters. Estimates of variances, heritabilities and genetic correlations from (1) large (~ 5 m²) drilled (LD) plots, (2) micro drilled (MD) plots, and (3) one-row plots of 4 spaced plants (SP) are reported. Thirty-eight single crosses of rye were grown at 2 locations for 2 years in LD, MD and SP plots replicated 2, 4 and 6 times, respectively. Genotypic differences were significant in all plot types for all agronomic and quality traits, although estimates of genetic variances were smaller in LD than MD or SP plots for grain yield, 32-spike weight and grains/spike. Heritabilities on an entry mean basis (0.62 to 0.95) were similar among plot types, but on a single plot basis estimates were lower for SP than for MD or LD plots. Genetic correlations were high between all 3 plot types, with correlations between LD and SP plots being approximately 1.0 for falling number, 1000-grain weight, and flowering date, 0.90 for grain yield, grains/spike, test weight and height, and 0.70 for tiller number. Based on the high heritabilities achieved in small plots and the close agreement between MD- or SP- with LD-plot performance it was concluded that greater use should be made of small plot types when selecting for yield and quality in winter ry

Fermentation kinetics of stems of sorghum and millet genotypes

Gas production profiles were obtained from in vitro fermentation of stems of six genotypes of sorghum and millet grown at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India. The ranking of sorghum and millet genotypes by cumulative gas production was consistent throughout the 96-hour fermentation period. However, differences were proportionally greater during the initial 3 and 6 h of fermentation. The multiphase model described by Groot et al. [Groot, J.C.J., Cone, J.W., Williams, B.A., Debersaques, F.M.A., Lantinga, E.A., 1996. Anim. Feed Sci. Technol. 64:77–89] was used to fit the in vitro fermentation gas observations of these substrates, and fermentation kinetics parameters were calculated using the fitted model. The final estimates of the model parameters (A, B, C), tested by varying the initial estimates obtained with the monophasic model by ±50%, were stable, showing no dependence on the starting values of the model parameters. However, in millet stems, the C parameter has shown a tendency to converge near unity. The stability of the final values of the parameters of the model in this study suggests the potential applicability of the multiphase model when only nine gas observations over a period of 96 h were available. However, the indeterminacy in the parameters of phase 1 for some millet stems indicates the need of an intermediate gas value between 0 and 3 h. In both, sorghum and millet the asymptotic gas of the first phase (A1) was negatively correlated with NDF (r = −0.82, p < 0.05; r = −0.80, p < 0.05, respectively) and lignin (r = −0.86, p < 0.05; r = −0.95, p < 0.01, respectively). The estimated maximum fractional rate of substrate digestion in the second phase (Rm2) showed a strong inverse relationship with lignin (r = −0.93, p < 0.01) in millet but not in sorghum. On the other hand, the time at which the rate of fermentation reached its maximum in phase 1 (tmax1) was negatively correlated with ADF and lignin (r = −0.88, p < 0.05 and r = −0.87, p < 0.05, respectively) in sorghum, whereas in millet only tmax2 (phase 2) was negatively correlated with lignin (r = −0.88, p < 0.05). Estimated differences in the contribution from the different phases to similar cumulative gas at 48 h in stems of different sorghum genotypes indicate the need to complement measurements of total gas production with selected kinetics parameters. The degree of variability between genotypes observed for kinetics parameters related to both, phases 1 and 2 suggest that these parameters have potential for discriminating feed quality differences between crop residues or plant parts. These results point out the difficulty in finding a single feed quality parameter to be used to rank different crop residues of different genotypes. Additional studies are needed to associate these parameters with voluntary intake and in vivo rumen outflow rates with which these phases could be associated

Structure of variation among morphological and physiological traits in three pearl millet composites

The plant breeder's task of improving and stabilizing many plant traits simultaneously is complicated by interrelationships that occur among the traits. Factor analyses were conducted on three phenotypically diverse pearl millet [Pennisetum glaucum (L.) R. Br.] composites to describe the structure of relationships among yield, morphological, and physiological traits. Approximately 1000 S0 spaced-plants from each composite were evaluated for 20 traits, and random samples of 289 S1 progenies from each composite were evaluated for 18 of these traits. Factors extracted in S0 and S1 populations identified unique sets of traits that were interrelated along axes of (a) biological yield, (b) panicle size, (c) dry matter partitioning and (d) compensation between number and size of seeds. Several plant traits had large loading coefficients on the ‘Biological Yield’ and also, but with opposite signs, on the ‘Dry Matter Partitioning’ factor. The traits having large loading on these two factors differed between space-planted and normal-density stands, showing that environmental conditions contributed to the associations observed among traits. Correlations of S1 with parental S0 factor scores for the ‘Biological Yield’, ‘Panicle Size’ and ‘Seed Paramters’ factors produced significant correlation coefficients, indicating that these trait complexes had a genetic basis. The implications of these results for millet breeding are discussed

Feasibility of Mass Selection in Pearl Millet

Mass selection is a technique widely used in both population and pedigree breeding of pearl millet, Pennisetum glaucum (L.) R. Br. To determine the feasibility of mass selecting for 19 agronomic traits of pearl millet, we (i) estimated trait heritabilities on both a single-plant and a progeny-mean basis and (ii) observed responses of S1 progenies to divergent selection on parental S0 plants. Fourteen hundred and forty S0 spaced plants from each of three pearl millet composites were self-pollinated and evaluated for 19 traits at Patancheru, India on a Udic Rhodostalf soil. Random samples of 289 S1 progenies from each S0 population were evaluated for these same traits in triple-lattice experiments at the same location. Heritabilities estimated on a progeny-mean basis were all significantly (P < 0.01) larger than zero. Heritabilities estimated on a single-plant basis were highest for traits such as panicle length (0.64), plant height (0.58), and seed weight (0.52); they were intermediate straw yield (0.40); and they were lowest for grain yield (0.29), threshing ratio (0.24), and harvest index (0.23), averaged across composites. Divergent selection of the highest and lowest decile of S0 plants identified S1 progenies with significantly (P < 0.05) increased and decreased means, respectively, for panicle and seed characteristics in all composites and for grain yield in two of the composites. Selection for increased efficiency of dry matter partitioning, however, was ineffective. The observed heritability values suggest that mass selection of pearl millet can be effective for all traits examined, with the rate of gain being proportional to the magnitude of those value

Getting the Most Out of Sorghum Low-Input Field Trials in West Africa Using Spatial Adjustment

Breeding sorghum for low-input conditions is hindered by soil heterogeneity. Spatial adjustment using mixed models can help account for this variation and increase precision of low-input field trials. Large small-scale spatial variation (CV 39.4 %) for plant available phosphorus was mapped in an intensely sampled low-input field. Spatial adjustments were shown to account for residual yield differences because of this and other growth factors. To investigate the potential of such models to increase the efficiency of low- and high-input field trials, 17 experiments with 70 sorghum genotypes conducted in Mali, West Africa, were analysed for grain yield using different mixed models including models with autoregressive spatial correlation terms. Spatial models (AR1, AR2) improved broad sense heritability estimates for grain yield, averaging gains of 10 and 6 % points relative to randomized complete block (RCB) and lattice models, respectively. The heritability estimate gains were even higher under low phosphorus conditions and in two-replicate analyses. No specific model was best for all environments. A single spatial model, AR1 × AR1, captured most of the gains for heritability and relative efficiency provided by the best model identified for each environment using Akaike's Information Criterion. Spatial modelling resulted in important changes in genotype ranking for grain yield. Thus, the use of spatial models was shown to have potentially important consequences for aiding effective sorghum selection in West Africa, particularly under low-input conditions and for trials with fewer replications. Thus, using spatial models can improve the resource allocation of a breeding program. Furthermore, our results show that good experimental design with optimal placement and orientation of blocks is essential for efficient statistical analysis with or without spatial adjustment

Cultivar mixtures: a means of exploiting morpho-developmental differences among cultivated groundnuts

Groundnut (Arachis hypogaea L.) cultivars vary greatly in maturity and growth habit. This morphological and developmental variability may provide opportunities for greater kernel and haulm yields by sowing mixtures of cultivars that interact synergistically. We used two genotypes from each of four growth-habit classes (Spanish, Valencia, Virginia bunch, and Virginia runner) to form two-cultivar (1:1) mixtures representing diverse maturity and growth-habit combinations. The mixtures, 12 in the 1983–1984 dry season, and 28 in the 1984 rainy season, were sown at three and two plant densities, respectively. Land Equivalent Ratios (ler) of mixtures showed that overcompensation was more frequent than undercompensation. The largest lers were 1.23 for pod yield, 1.29 for kernel yield, and 1.18 for haulm yield average over planting densities in the rainy season. Intersubspecific combinations that gave diversity for both maturity and growth habit exhibited synergistic interactions most frequently. However, this intergenotypic interaction was specific to the genotypes involved. Investigation of cultivar mixtures in groundnuts should focus on stability rather than maximization of yield since no mixture yield surpassed that of the highest-yielding variety

Sorghum cultivation and improvement in West and Central Africa

The diversity of sorghum cultivated in Africa attests to the African origin of this crop. Ten to 25 or more varieties of sorghum may be cultivated as distinct pure stands in a single village in Mali (Siart, 2008) or Burkina Faso (Barro-Kondombo et al., 2010). In Northern Cameroon, varietal mixtures are cultivated, with each mixture containing 12 varieties on average (Barnaud et al., 2006). Farmers have developed strategies for using varietal diversity to minimize risk and maximize productivity in the context of complex and diverse adaptive challenges, strategies developed over several thousand years of cultivating sorghum. The diversity of sorghum types cultivated reflects the wide and contrasting ecosystems in which it is cultivated and the range of ways it is used (Rooney, 2004)..