Testcross Research Articles

Inheritance of downy mildew resistance and its relationship with biochemical traits in cauliflower (Brassica oleracea L. var. botrytis)

Downy mildew (DM) is a destructive disease of cauliflower and other Brassica vegetables that not only affects young seedlings and transplanted crop but also produces damaging abnormalities in the inflorescence of infected seed crops. The development of resistant cultivars is an alternative to control phytosanitary problems that affect cauliflower crop. This study was conducted to investigate the mode of inheritance of resistance to DM in cauliflower under field conditions and its association with biochemical traits. Six generations derived from hybridization between four diverse genotypes, namely DPCaY-3 (susceptible), Palam Uphar (susceptible), DPCaY-8 (resistant), and DPCaY-6 (resistant), were evaluated in the randomized block design along with standard check. The result of this study provided an indication that DM resistance was conditioned by a single dominant gene. In DPCaY-3 × DPCaY-8, DPCaY-3 × DPCaY-6, and PU × DPCaY-6, the segregation of F2 generations was in the ratio 3(R):1(S), which suggests the monogenic inheritance of resistance in these crosses. This was further confirmed by the test cross ratio of 1(R):1(S) in a backcross with the susceptible parent in all the three crosses. Correlation matrix revealed that plant disease (DM) index (PDI) exhibited significant and positive association with total sugars, whereas vitamin C and total phenols exhibited significant and negative relationship with PDI. This exemplifies the significance of these phytochemicals in plant-defense mechanism against pathogens.

Inheritance of parthenocarpy in gynoecious cucumber (Cucumis sativus L.) cultivar PPC-2

The gynoecious and parthenocarpic inbred line, Pant Parthenocarpic Cucumber-2 (PPC- 2) was crossed with Indian monoecious and non-parthenocarpic cultivar Pusa Uday to develop F1, F2, B1 and B2 to determine the inheritance of parthenocarpy.The crop was grown under insect proof net house of 40 mesh. The pistillate buds were covered using butter paper bags before anthesis to prevent out-crossing.The observations were recorded separately for the development of early parthenocarpic fruits (i.e.1-7th nodes), late parthenocarpy (8th and above nodes) and non-parthenocarpic fruits. In F1 generation, out of 40 plants screened, 2 plants produced parthenocarpic fruits at lower nodes (1-7th nodes), 37 plants produced parthenocarpic fruits at upper nodes (8th and above), whereas,only 1 plant that did not produced any fruit was considered as non-parthenocarpic. The segregation of F2 population and test crosses for parthenocarpic fruit development suggested that parthenocarpy in gynoecious and parthenocarpic cucumber line PPC-2 is under the control of incomplete dominant gene.

Assessing heuristic models through k-fold testing approach for estimating scour characteristics in environmental friendly structures

Scouring downstream of grade control structure is a common problem. W-weir structures are recommended for controlling, reducing soil erosion, and development aquatic organisms habitat. W-weir structures can provide energy dissipation, increased aquatic habitat, grade-control, and bank and bed stabilization through the diversion of conveyance with the river-channel center. The current study aimed at analyzing the scour geometry downstream of W-weirs in the sinuous channels using heuristic gene expression programming (GEP) and support vector machine (SVM) models. A comparison was also made between the GEP and SVM with traditional multi variable linear regression (MLR) technique. The cross-validation technique (i.e. k-fold testing) was used to assess the developed models. Observations revealed that the scour typology affects the maximum scour depth value. The obtained results showed that both the GEP and SVM models give promising results in simulating the scour depth and scour length magnitudes. Assessing the models confirmed that using the k-fold testing cross validation is very necessary as all the available patterns can participate in training and testing stages, which reduces the risk of over fitting.

Genetic dissection of main and epistatic effects of QTL based on augmented triple test cross design.

The use of heterosis has considerably increased the productivity of many crops; however, the biological mechanism underpinning the technique remains elusive. The North Carolina design III (NCIII) and the triple test cross (TTC) are powerful and popular genetic mating design that can be used to decipher the genetic basis of heterosis. However, when using the NCIII design with the present quantitative trait locus (QTL) mapping method, if epistasis exists, the estimated additive or dominant effects are confounded with epistatic effects. Here, we propose a two-step approach to dissect all genetic effects of QTL and digenic interactions on a whole genome without sacrificing statistical power based on an augmented TTC (aTTC) design. Because the aTTC design has more transformation combinations than do the NCIII and TTC designs, it greatly enriches the QTL mapping for studying heterosis. When the basic population comprises recombinant inbred lines (RIL), we can use the same materials in the NCIII design for aTTC-design QTL mapping with transformation combination Z1, Z2, and Z4 to obtain genetic effect of QTL and digenic interactions. Compared with RIL-based TTC design, RIL-based aTTC design saves time, money, and labor for basic population crossed with F1. Several Monte Carlo simulation studies were carried out to confirm the proposed approach; the present genetic parameters could be identified with high statistical power, precision, and calculation speed, even at small sample size or low heritability. Additionally, two elite rice hybrid datasets for nine agronomic traits were estimated for real data analysis. We dissected the genetic effects and calculated the dominance degree of each QTL and digenic interaction. Real mapping results suggested that the dominance degree in Z2 that mainly characterize heterosis showed overdominance and dominance for QTL and digenic interactions. Dominance and overdominance were the major genetic foundations of heterosis in rice.

Detection of epistasis through triple test cross (TTC) analysis in maize (Zea mays L.)

The present study was carried out to detect the epistasis present in two cross of maize through triple test cross (TTC) analysis. The mean squares due to total epistasis was highly significant at P?0.01 for all the characters in both C-I and C-II, except for ear length in C-I. The i type of epistasis was highly significant for the traits such as days totasseling, days to silking, earlength, ear circumference, kernels row-1,100 grain weight and shelling percentage in C-I and in C-II, ‘i’ type was non-significant for ASI, ear length, kernels row-1and grain yield plot-1. Both j type and l type of epistasis were significant for all characters in both C-I and C-II, except for ear length in C-I and days to silking in C-II. The estimate of additive genetic component (D) was highly significant for all characters in both C-I and C-II. Epistasis played a significant role in the inheritance of all the characters in both C-I and C-II except for ear length in C-I. Both additive and dominance components of genetic variance with a predominance of dominance genetic variance played an important role in the inheritance of all the quantitative traits except ear length in C-I and kernel rows ear-1 in C-II.

Study of combining ability of forage sorghum genotypes based on biochemical composition of biomass and grain

The article discusses the results of the evaluation of combining the ability of forage sorghum varieties in test-crosses with CMS-lines of grain sorghum A2 O-1237, A2 AGS, and A2 KVV114. The experiment included forage sorghum varieties (11), CMS-lines (3), and tester hybrids (33) of F1 generation. The differentiation of varieties and hybrids based on sugar content in the stem juice and protein, fat, fiber, ash and NFE in biomass and grain was performed using statistical methods, and GCA and SCA parameters were calculated. The use of forage sorghum varieties in breeding programs for the improvement of the biochemical composition of grain and biomass hybrids of the F1-generation and synthetic varieties-populations was considered. GCA and SCA variability of the content of sugars in juice of the stem detected in genotypes allows using them in breeding programs. Chayka, k-592, and k-2963 varieties are effective in breeding for the production of synthetic varieties and unsuitable for the production of hybrids with high-sugar content, since they are characterized by high GCA but relatively low variance of SCA. In breeding for heterosis by sugar content in the stem juice, most promising were L-2, L-10, and L-69 lines. Varieties k-6 and L-7 with high values of GCA effect and variances of SCA were suitable for the use in breeding of synthetics varieties and F1 hybrids. It was demonstrated that, in breeding of sorghum varieties, the test cross method allows identifying GCA and SCA indexes of the best lines and providing a more rigorous analysis of experimental data.

Evaluation of new inbreds for fertility restoring and maintaining behaviours in two diverse CMS sources of sunflower (Helianthus annuus L.)

Eight cytoplasmic male sterile (CMS) lines of sunflower (Helianthus annuus L.) belonging to two different sources of cytoplasmic male sterility, PET-1 (H. petiolaris) (CMS-852A, CMS-7-1A, CMS-234A, CMS-2A, COSF-1A, COSF-7A and CMS-10A) and CMS I (H. lenticularis) (IMS-852A) were crossed with newly developed 20 inbred lines to identify the maintainer or restorer behaviour in Line x Tester fashion and evaluation of test cross progenies was conducted. The presence or absence of pollen in F1 s was recorded in the field whereas pollen fertility was confirmed in the laboratory by acetocarmine staining test. All the inbredswere categorized into complete, partial restorer and maintainer through cytological observation. Twelve inbreds viz., RHAGKVK-1, RHAGKVK-2, AKSFI-49-3, AKSFI-49-4, AKSFI-46-2, HOHAL-37,CSFI-5134,CSFI-5055, CSFI-5133, CSFI-5185, CSFI-5075and Selection-I restored the fertility for most of the PET-1 CMS lines, while CSFI-5033, IB0-50, IB-60, IB-61, IB-67 and IB-101 inbreds maintained sterility. The second CMS line IMS-852A, was maintained by 13 inbreds indicating involvement of different gene(s), while one inbred CSFI-5134 was restored its fertility. Some of the inbreds (AKSFI-49-3 and AKSFI-49-4) were behaved as partial restorers for CMS-10A. The range of fertility restoration in different cross combinations was between 46.6 and 99.5 per cent. In the present study 50 to 65 per cent frequency of pollen fertility was reported for PET-1. However, only 5 per cent frequency of pollen fertility was observed for CMS I. From the study it was evident that among the two CMS sources, restorers for CMS I are rather scarce. Efforts should be made to locate restorers for CMS I for its utilization in production of more productive sunflower hybrids

Identification of best restorers and maintainers in rice genotypes through test cross nursery

Identification of best restorers and maintainers in rice genotypes through test cross nursery

Functional Marker Assisted Improvement of Stable Cytoplasmic Male Sterile Lines of Rice for Bacterial Blight Resistance.

Bacterial blight (BB), caused by Xanthomonas oryzae pv.oryzae is one among the major diseases in rice, which in severe condition cause losses up to 60% in total yield. Marker assisted pyramiding of three broad spectrum BB resistance genes (xa5, xa13, and Xa21) in prominent rice varieties is the most economical and effective strategy for the management of the BB disease. We report here the pyramiding of three genes (xa5, xa13, and Xa21) in maintainer lines (CO 2B, CO 23B, and CO 24B) of three promising wild abortive cytoplasmic male sterile lines (CO 2A, CO 23A, and CO 24A) through functional markers assisted back cross breeding. IRBB60 with xa5, xa13, and Xa21 genes is used as a donor parent. BC2F1 and BC2F2 generations from a cross of CO 2B, CO 23B, and CO 24B with IRBB60 were evaluated for bacterial blight and non-fertility restoration. In BC2F1, plants with all three resistance genes (xa5, xa13, and Xa21) and high parent genome recovery was identified. In BC2F2, plants with all resistance genes and without fertility restorer (Rf3 and Rf4) were selected. Based on agronomic traits, BB resistance and maintenance of sterility, two plants each in CO 2B × IRBB60, CO 24B × IRBB60 and one plant in CO 23B × IRBB60 combinations were identified. The identified lines were crossed with respective male sterile lines for conversion of improved B line into CMS line through back-crossing, in addition to selfing. The plants with high recurrent genome and phenotypically similar to parental lines and sterile are being used for the hybrid rice development program. Currently, using these lines (improved CMS line), test crosses were made to develop new rice hybrids. Hybrids combinations viz., CO 23A × AD08009R and CO 24A × IET20898R were found to be stable at different locations with high yield. The R line used in this study has been introgressed with xa5, xa13, and Xa21 genes in a separate breeding program. These new hybrids with resistance against bacterial blight will increase the crop production at BB environment.

Inheritance of resistance to downy mildew by F1 and F2 sunflower hybrids

Inheritance of resistance to downy mildew by F1 and F2 sunflower hybrids

Identification of Light-Independent Anthocyanin Biosynthesis Mutants Induced by Ethyl Methane Sulfonate in Turnip "Tsuda" (Brassica rapa).

The epidermis of swollen storage roots in purple cultivars of turnip “Tsuda” (Brassica rapa) accumulates anthocyanin in a light-dependent manner, especially in response to UV-A light, of which the mechanism is unclear. In this study, we mutagenized 15,000 seeds by 0.5% (v/v) ethyl methane sulfonate (EMS) and obtained 14 mutants with abnormal anthocyanin production in their epidermis of swollen storage roots. These mutants were classified into two groups: the red mutants with constitutive anthocyanin accumulation in their epidermis of storage roots even in underground parts in darkness and the white mutants without anthocyanin accumulation in the epidermis of storage roots in aboveground parts exposed to sunlight. Test cross analysis demonstrated that w9, w68, w204, r15, r21, r30 and r57 contained different mutations responsible for their phenotypic variations. Further genetic analysis of four target mutants (w9, w68, w204 and r15) indicated that each of them was controlled by a different recessive gene. Intriguingly, the expression profiles of anthocyanin biosynthesis genes, including structural and regulatory genes, coincided with their anthocyanin levels in the epidermis of storage roots in the four target mutants. We proposed that potential genes responsible for the mutations should be upstream factors of the anthocyanin biosynthesis pathway in turnips, which provided resources to further investigate the mechanisms of light-induced anthocyanin accumulation.

Evaluation of the role of surface pretreatments on the corrosion process. Correlation between conventional and electrochemical tests

The influence on the anticorrosion properties of three different pretreatments applied on steel panels, before being powder‐paint coated, is investigated both by conventional tests (cross cut, impact resistance, and neutral salt spray tests) and electrochemical tests (electrochemical impedance spectroscopy (EIS) and accelerated cyclic electrochemical technique (ACET)). Amorphous phosphate, microcrystalline phosphate, and a sol‐gel, based on 3‐aminopropyltriethoxysilane (APTES), were the different pretreatments that were analyzed. All of them were compared with a non‐pretreated coated carbon steel panel. The microcrystalline phosphate, followed by the sol‐gel surface treatments, showed the best system properties. These good results are attributed to ions available at the interface, and to covalent bonds generated by the silicon network and the substrate surface, respectively.

Erratum to: Identification of molecular variants of the nonrestoring restorer-of-fertility 1 allele in sugar beet (Beta vulgaris L.).

Only three variants of nonrestoring alleles for sugar beet Rf1 were found from the US maintainer lines which were the selections from a broad range of genetic resources. Cytoplasmic male sterility is widely used for hybrid breeding of sugar beets. Specific genotypes with a nonsterility-inducing cytoplasm and a nonrestoring allele of restorer-of-fertility gene (rf) are called maintainers. The infrequent occurrence of the maintainer genotype evokes the need to diagnose rf alleles. Molecular analysis of Rf1, one of the sugar beet Rfs, revealed a high level of nucleotide sequence diversity, but three variants were tightly associated with maintainer selection in Japan. The question was raised whether this small number of variants would be seen in cases where a wider range of genetic resources was used for maintainer selection. Fifty-seven accessions registered as maintainers in the USDA germplasm collection were characterized in this study. Mitochondrial DNA types (mitotypes) of 551 plants were diagnosed based on minisatellite polymorphism. A mitotype associated with sterility-inducing (S) cytoplasm was identified in 58 plants, indicating S-cytoplasm contamination. The organization of rf1 was investigated by two PCR markers and DNA gel blot analysis. Eight haplotypes were found among the US maintainers, but subsequently two haplotypes were judged as restoring alleles after a test cross and another haplotype was not inherited by the progeny. Nucleotide sequences of rf1 regions in the remaining five haplotypes were compared, and despite the sequence diversity of the gene-flanking regions, the gene-coding regions were identified to be three types. Therefore, there are three rf1 variants in US maintainers, the same number as in the Japanese sugar beet germplasm collection. The implications of having a small repertoire of rf1 variants are discussed.

Inheritance of pod shattering in soybean [Glycine max (L.) Merrill.

In the present investigation, inheritance of pod shattering in soybean was studied in three crosses involving four parents, among them MACS-450 and DS-9712 were tolerant to pod shattering while Monetta and Kalitur were susceptible to pod shattering. The contrasting parents were used to develop three cross combinations viz., Monetta × MACS-450, Kalitur × DS-9712 and Kalitur × MACS-450. Inheritance of pod shattering was found to be governed by partial dominance of susceptibility over the resistance. Two major genes with inhibitory epistasis were involved in inheritance of pod shattering in soybean. As regardsto inheritance of pod shattering tolerance parents MACS-450 and DS-9712, F1s of susceptible × resistant crosses and backcrosses with resistant parent showed tolerance. Two major genes with inhibitory epistasis were involved in inheritance of pod shattering in soybean as evidenced from F2 ratio (13:3) and confirmed by test cross ratio (3:1) in tolerant × susceptible crosses. Two dominant genes with inhibitory epistasis were involved in the inheritance of pod shattering tolerance in soybean.

Simple genetic inheritance conditions resistance to Liriomyza sativae in melon

The leafminer Liriomyza sativae (Diptera: Agromyzidae) stands out as the main plant health problem in melon in the Northeast region of Brazil, which is the main region for production and export of the fruit. Genetic resistance of plants is an important strategy in management of this pest. The plant BAGMEL 56-R was selected as a new source of resistance to L. sativae through antibiosis; this resistance is characterized by the death of larvae soon after they begin feeding on the leaf mesophyll; the result is leaf mines that are small and insignificant in terms of yield reduction. Lines with contrasting levels of resistance were obtained from the progenies of this source of resistance through successive self-pollinations, conducted by the pedigree breeding method. Through the segregation pattern of the progenies and the test cross, the genetic nature of resistance was determined; one gene with complete dominance conditions resistance. The name Liriomyza sativae resistance and the symbol Ls are suggested to represent this new gene. In addition, through a non-preference test with lines in contrast for antibiosis and the susceptible hybrid ‘Goldex’, the presence of antixenosis was observed in this source of resistance. Probably, these different types of resistance in the source BAGMEL 56-R are associated with distinct defense mechanisms. Therefore, with this new source, introgression of resistance to L. sativae in elite lines or commercial hybrids of melon is possible.

Molecular stacking of wide compatibility gene, S5 n and elongated uppermost internode (eui) gene into IR 58025B, an elite maintainer line of rice

One of the most widely used and stable wild-abortive cytoplasmic male sterile (WA-CMS) line is IR 58025A. We had earlier transferred the gene (eui1) for elongated uppermost internode into the elite WA-CMS line named IR 58025eB with the help of markers. To overcome incomplete panicle exsertion in the WA-CMS line and better exploitation of indica/japonica heterosis, we have stacked a major gene for wide-compatibility (S5 n ) into IR 58025eB through marker-assisted breeding. SSR markers (RM5970) tightly linked to eui1 gene and (S5-InDel) functional maker of S5 n gene were used for foreground selection, while ninety-one microsatellite markers polymorphic between IR 58025eB and donor Dular (S5 n ) were utilized for background selection at each backcross generation and backcrossing was continued till BC3 generation. Phenotypic observation previous to background selection at each generation provided supplementary information for identifying the novel recombinants and the fast-tracked recurrent parent genome recovery which ranged from 94.50 to 96.70% in selected BC3F4 plants. At BC3F5 generation, seven stable, backcross-derived lines possessing S5 n and eui genes, high yield, and long-slender grain type have been identified; their maintainer ability was confirmed through test crosses. These improved lines are being converted to CMS lines by marker-assisted backcrossing.

Antigenotoxicity of Depsidones Isolated from Brazilian Lichens

Although phenolic compounds produced by lichens have been widely investigated in antitumor assays, only a small number have been evaluated for mutagenicity and genotoxicity. This study evaluated protocetraric, hypostictic, psoromic, and salazinic acids for their potential genotoxic or antigenotoxic activity against somatic cells of Drosophila melanogaster . These compounds were isolated from the lichens Parmotrema dilatatum, Pseudoparmelia sphaerosphora, Usnea jamaicensis, and Parmotrema cetratum , respectively, collected from the Brazilian Cerrado biome. The compounds were evaluated at 0.75, 1.5, 3.0, and 6.0 mmol L –1 using the SMART test, employing standard and high-bioactivation crosses of Drosophila melanogaster. Doxorubicin (DXR) was the positive control. Psoromic and salazinic acids proved toxic at 6.0 mM. None of the compounds evaluated exhibited mutagenicity, but each of them significantly reduced genetic damage caused by DXR, proving antigenotoxic when tested on somatic cells of D. melanogaster . DOI: http://dx.doi.org/10.17807/orbital.v9i1.897

Combining ability and testcross performance of drought-tolerant maize inbred lines under stress and non-stress environments in Kenya.

Drought and poor soil fertility are among the major abiotic stresses affecting maize productivity in sub‐Saharan Africa. Maize breeding efforts at the International Maize and Wheat Improvement Center (CIMMYT) have focused on incorporating drought stress tolerance and nitrogen‐use efficiency (NUE) into tropical maize germplasm. The objectives of this study were to estimate the general combining ability (GCA) and specific combining ability (SCA) of selected maize inbred lines under drought stress (DS), low‐nitrogen (LN) and optimum moisture and nitrogen (optimum) conditions, and to assess the yield potential and stability of experimental hybrids under these management conditions. Forty‐nine experimental three‐way cross hybrids, generated from a 7 × 7 line by tester crosses, and six commercial checks were evaluated across 11 optimum, DS and LN sites in Kenya in 2014 using an alpha lattice design with two replicates per entry at each site. DS reduced both grain yield (GY) and plant height (PH), while anthesis–silking interval (ASI) increased under both DS and LN. Hybrids ‘L4/T2’ and ‘L4/T1’ were found to be superior and stable, while inbreds ‘L4’ and ‘L6’ were good combiners for GY and other secondary traits across sites. Additive variance played a greater role for most traits under the three management conditions, suggesting that further progress in the improvement of these traits should be possible. GY under optimum conditions was positively correlated with GY under both DS and LN conditions, but GY under DS and LN was not correlated. Our results suggest the feasibility for simultaneous improvement in grain yield performance of genotypes under optimum, DS and LN conditions.

Use of Genomic Estimated Breeding Values Results in Rapid Genetic Gains for Drought Tolerance in Maize.

More than 80% of the 19 million ha of maize ( L.) in tropical Asia is rainfed and prone to drought. The breeding methods for improving drought tolerance (DT), including genomic selection (GS), are geared to increase the frequency of favorable alleles. Two biparental populations (CIMMYT-Asia Population 1 [CAP1] and CAP2) were generated by crossing elite Asian-adapted yellow inbreds (CML470 and VL1012767) with an African white drought-tolerant line, CML444. Marker effects of polymorphic single-nucleotide polymorphisms (SNPs) were determined from testcross (TC) performance of F families under drought and optimal conditions. Cycle 1 (C1) was formed by recombining the top 10% of the F families based on TC data. Subsequently, (i) C2[PerSe_PS] was derived by recombining those C1 plants that exhibited superior per se phenotypes (phenotype-only selection), and (ii) C2[TC-GS] was derived by recombining a second set of C1 plants with high genomic estimated breeding values (GEBVs) derived from TC phenotypes of F families (marker-only selection). All the generations and their top crosses to testers were evaluated under drought and optimal conditions. Per se grain yields (GYs) of C2[PerSe_PS] and that of C2[TC-GS] were 23 to 39 and 31 to 53% better, respectively, than that of the corresponding F population. The C2[TC-GS] populations showed superiority of 10 to 20% over C2[PerSe-PS] of respective populations. Top crosses of C2[TC-GS] showed 4 to 43% superiority of GY over that of C2[PerSe_PS] of respective populations. Thus, GEBV-enabled selection of superior phenotypes (without the target stress) resulted in rapid genetic gains for DT.

English

The doubled haploid (DH) technology enables maize breeders to develop a large number of homozygous lines rapidly and test them in hybrid combinations early in the breeding cycle. The objectives of this study were to evaluate testcross performance of 556 DH lines derived from 10 diverse tropical backcross (BC1) populations, and to estimate variance components and broad-sense heritability under both well-watered and managed drought-stress conditions in Kenya. The 556 DH testcrosses were divided into six trials, with each trial comprising 84 to 126 entries and six commercial checks developed through conventional pedigree method. Trials were evaluated at 3 or 4 well-watered (WW) and two managed drought-stress (WS) sites in 2012 using an alpha lattice design with three replications per environment. Test crosses of the DH lines showed significant differences in grain yield and other agronomic traits. In the combined analysis across the WW locations, the top 10 DH testcrosses from each trial gave 0.6 to 32.7% higher grain yield than the best commercial check. Under managed drought-stress condition, the top 10 DH testcrosses from each trial gave 11.8 to 40.9% more grain yield than the best check. The best DH lines identified in the study could be used in tropical maize breeding programs in Africa for improving grain yield and drought-tolerance. Following evaluation in advanced testing and national performance trials (NPT), a total of 36 hybrids involving DH lines from this study were recommended for commercial cultivation in east and southern Africa. Key words: Africa, heritability, managed drought-stress, testcrosses.